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In the field of sustainable architecture, transformability is an important way of actively responding to ambient conditions while also meeting the needs of occupants and addressing issues of building performance. This research contributes knowledge for architects about the potential of kinetics for the shading system to respond effectively to changes in its environment. Within contemporary architecture, there is a growing interest in motion; buildings and their parts are gradually shifting from static to dynamic. However, contemporary activities in architecture are evidence of a lack of a holistic approach to the design of motion in architecture and the design of motion as an alternative mode of design thinking is still in its infancy. Consequently, the existing tradition of static forms being the sole forms taught in architectural studies should be reevaluated as a design strategy. This research is a step in the direction of better understanding the key knowledge exchanges within the design process of transformable shading systems. It will seek to investigate, explore, and propose how the concept of transformability in designing shading systems can be suggested, depicted, or physically incorporated in building envelopes. In order to get the full potential of the design process of transformable shading systems, this study presents a design workflow of a specific case, called AURA, that helps to create openings for establishing a proper design methodology of transformable shading systems. While the workflow will be concerned with identifying the key decision nodes, it is anticipated that in-depth development will determine critical parameters addressing transformation itself as a design parameter of transformable shading systems. Two studio-based courses offered at Virginia Tech and Texas AandM by the author will become a testing ground for evaluating the key decision nodes found in the design process of AURA within the context of architectural programs, bringing forth the opportunity to expand the current domain of transformable shading systems to a broader perspective of architecture pedagogy. In this case, this research is a step towards adding values directly into the content of the curricula, and thus into the field of design education as a whole.' Ph. D.

This thesis focuses on the detailed design, implementation, and testing of a unique high performance rotary actuator for use in a custom haptic force feedback device. This six degree of freedom (DoF) position input and three DoF force output haptic device is specifically designed to recreate force sensations with the goal of improving operator performance in remote or simulated environments. By upholding the strict design principles of an ideal force-source actuator, the developed actuator and consequently the haptic controller can successfully replicate forces accurately and realistically. In the comprehensive presentation of this design, numerous analytical tools are also developed and presented with the intention of them being resourceful in the design or improvement of other haptic actuators, specifically cable-driven force feedback designs. These tools which include a linear system model can be valuable not only in the development but in the control of cable-driven actuators. Due to the imposed design criteria, the developed 1.045 Nm (1.359 Nm peak) cable-driven sectorial rotary actuator exhibits numerous properties that are desired in an open-loop force controlled actuator. These properties include low inertia (6.53e-04 kgm^2), low perceived mass (0.102 kg), small torque resolution (3.84e-04 Nm), small position resolution (21.5 arcsec), and high bandwidth (300 Hz). Due to the efficient cable transmission the design is also backdrivable, isotropic, low friction, and zero backlash. As a result of these numerous intrinsic properties, a high fidelity force feedback haptic actuator was conceived and is presented in this thesis. Master of Science

The focus of Location-Aware Adaptive Vehicle Dynamics System (LAAVDS) research is to develop a system to avoid situations in which the vehicle exceeds its handling capabilities. The proposed method is predictive, estimating the ability of the vehicle to successfully navigate upcoming terrain, and it is assumed that the future vehicle states and local driving environment is known. An Intervention Strategy must be developed such that the vehicle is navigated successfully along a road via modest changes to the driver's commands and do so in a manner that is in harmony with the driver's intentions and not in a distracting or irritating manner. Clearly this research relies on the numerous new technologies being developed to capture and convey information about the local driving environment (e.g., bank angle, elevation changes, curvature, and friction coefficient) to the vehicle and driver. Ph. D.

The following study focuses on the design and validation of an underactuated robotic gripper built for the Tactical Hazardous Operations Robot (THOR). THOR is a humanoid robot designed for use in the DARPA Robotics Challenge (DRC) and the Shipboard Autonomous Fire Fighting Robot (SAFFiR) project, both of which pertain to completing tasks associated with disaster response. The gripper was designed to accomplish a list of specific tasks outlined by the DRC and SAFFiR project. Underactuation was utilized in the design of the gripper to keep its complexity low while acquiring the level of dexterity needed to complete the required tasks. The final gripper contains two actuators, two underactuated fingers and a fixed finger resulting in four total degrees of freedom (DOF). The gripper weighs 0.68 kg and is capable of producing up to 38 N and 62 N on its proximal and distal phalanges, respectively. The gripper was put through a series of tests to validate its performance pertaining to the specific list of tasks it was designed to complete. The results of these tests show the gripper is in fact capable of completing all the necessary actions but does so within some limitations. Master of Science

Series elastic actuators (SEAs) have numerous benefits for force controlled robotic applications. This thesis presents the design and assembly of a set of compact, lightweight, low-friction linear SEAs for the legs of the Tactical Hazardous Operations Robot (THOR). The THOR SEA pairs a ball screw driven linear actuator with a configurable titanium leaf spring. A removable pivot changes the effective cantilever length, setting the compliance to either 372 or 655 kN/m. Unlike typical SEAs which measure actuator load through spring deflection, an in-line axial load cell directly measures actuator forces up to the commandable peak of 2225 N. The continuous operating range of the actuator is computed, along with an evaluation of the range of motion and torque profiles for the parallel hip and ankle joints. With a focus on a large power-to-weight ratio and small packaging size, the THOR SEAs are well-suited for accurate torque control of the parallel joints on the robot. Linearly actuated joints, especially ones driven through a crank arm, tend to suffer from a loss of mechanical advantage toward the ends of its limited range of motion. To augment the range of motion and mechanical advantage profile on THOR, an inverted Hoeken's linkage straight line mechanism is paired with a linear SEA at the hip and knee pitch joints on the robot. The resulting linkage assembly is capable of delivering nearly constant peak torque of 115 Nm across its 150 degree range of motion. The mechanical advantage profile of the Hoeken's linkage actuator is computed for the nominal case, as well the deviation resulting from maximum deflection of the titanium beam. Master of Science

The work seeks toward further developing a novel robotic platform capable of stable three legged locomotion. This will be accomplished by creating a robust and adaptable robotic platform capable of executing different walking strategies and taking multiple continuous steps. Previous iterations of this platform have been developed, all of which have used a single gait strategy. This study will seek to develop two new strategies. The first of which is a modification of the original strategy with theoretically improved gate robustness. A second strategy will seek to implement more advanced control techniques to create a fully stable balanced gait. Master of Science

With the ability to navigate natural and man-made environments and utilize standard human tools, humanoid robots have the potential to transform emergency response and disaster relief applications by serving as first responders in hazardous scenarios. Such applications will require major advances in humanoid control, enabling robots to traverse difficult, cluttered terrain with both speed and stability. To advance the state of the art, this dissertation presents a complete dynamic locomotion and whole-body control framework for compliant (torque-controlled) humanoids. We develop low-level, mid-level, and high-level controllers to enable low-impedance balancing and walking on compliant and uneven terrain. For low-level control, we present a cascaded joint impedance controller for series elastic humanoids with parallel actuation. A distributed controller architecture is implemented using a dual-axis motor controller that computes desired actuator forces and motor currents using simple models of the joint mechanisms and series elastic actuators. An inner-loop force controller is developed using feedforward and PID control with a model-based disturbance observer, enabling naturally compliant behaviors with low joint impedance. For mid-level control, we implement an optimization-based whole-body control strategy assuming a rigid body model of the robot. Joint torque setpoints are computed using an efficient quadratic program (QP) given desired joint accelerations, spatial accelerations, and momentum rates of change. Constraints on the centroidal dynamics, contact forces, and joint limits ensure admissibility of the optimized setpoints. Using this approach, we develop compliant standing and stepping behaviors based on simple feedback controllers. For high-level control, we present a dynamic planning and control approach for humanoid locomotion using a novel time-varying extension of the Divergent Component of Motion (DCM). By varying the natural frequency of the DCM, we are able to achieve generic vertical center of mass (CoM) trajectories during walking. Complementary reverse-time integration and model predictive control (MPC) strategies are proposed to generate dynamically feasible DCM plans over a multi-step preview window, supporting locomotion on uneven terrain. The proposed approach is validated through experimental results obtained using THOR, a 34 degree of freedom (DOF) series elastic humanoid. Rough terrain locomotion is demonstrated in simulation, and compliant locomotion and push recovery are demonstrated in hardware. We discuss practical considerations that led to a successful implementation on the THOR hardware platform and conclude with an application of the presented control framework for humanoid firefighting onboard the ex-USS Shadwell, a decommissioned Navy ship. Ph. D.

Recent advancements in actuator technologies, computation, and control have led to major leaps in capability and have brought humanoids ever closer to being feasible solutions for real-world applications. As the capabilities of humanoids increase, they will be called on to operate in unstructured real world environments. This realization has driven researchers to develop more dynamic, robust, and adaptable robots. Compared to state-of-the-art robots, biological systems demonstrate remarkably better efficiency, agility, adaptability, and robustness. Many recent studies suggest that a core principle behind these advantages is compliance, yet there are very few compliant humanoids that have demonstrated successful walking. The work presented in this dissertation is based on several years of developing novel actuators for two full-scale linearly actuated compliant humanoid robots, SAFFiR and THOR. Both are state-of-the-art robots intended to operate in the extremely challenging real world scenarios of shipboard firefighting and disaster response. The design, modeling, and control of actuators in robotics application is critical because the rest of the robot is often designed around the actuators. This dissertation seeks to address two goals: 1) advancing the design of compliant linear actuators that are well suited for humanoid applications, and 2) developing a better understanding of how to design and model compliant linear actuators for use in humanoids. Beyond just applications for compliant humanoids, this research tackles many of the same design and application challenges as biomechanics research so it has many potential applications in prosthetics, exoskeletons, and rehabilitation devices. Ph. D.

Firefighting robots are actively being researched to reduce firefighter injuries and deaths as well as increase their effectiveness on performing tasks. There has been difficulty in developing firefighting robots that autonomously locate a fire inside of a structure that is not in the direct robot field of view. The commonly used sensors for robots cannot properly function in fire smoke-filled environments where high temperature and zero visibility are present. Also, the existing obstacle avoidance methods have limitations calculating safe trajectories and solving local minimum problem while avoiding obstacles in real time under cluttered and dynamic environments. In addition, research for characterizing fire environments to provide firefighting robots with proper headings that lead the robots to ultimately find the fire is incomplete. For use on intelligent firefighting robots, this research developed a real-time local obstacle avoidance method, local dynamic goal-based fire location, appropriate feature selection for fire environment assessment, and probabilistic classification of fire, smoke and their thermal reflections. The real-time local obstacle avoidance method called the weighted vector method is developed to perceive the local environment through vectors, identify suitable obstacle avoidance modes by applying a decision tree, use weighting functions to select necessary vectors and geometrically compute a safe heading. This method also solves local obstacle avoidance problems by integrating global and local goals to reach the final goal. To locate a fire outside of the robot field of view, a local dynamic goal-based 'Seek-and-Find' fire algorithm was developed by fusing long wave infrared camera images, ultraviolet radiation sensor and Lidar. The weighted vector method was applied to avoid complex static and unexpected dynamic obstacles while moving toward the fire. This algorithm was successfully validated for a firefighting robot to autonomously navigate to find a fire outside the field of view. An improved 'Seek-and-Find' fire algorithm was developed using Bayesian classifiers to identify fire features using thermal images. This algorithm was able to discriminate fire and smoke from thermal reflections and other hot objects, allowing the prediction of a more robust heading for the robot. To develop this algorithm, appropriate motion and texture features that can accurately identify fire and smoke from their reflections were analyzed and selected by using multi-objective genetic algorithm optimization. As a result, mean and variance of intensity, entropy and inverse difference moment in the first and second order statistical texture features were determined to probabilistically classify fire, smoke, their thermal reflections and other hot objects simultaneously. This classification performance was measured to be 93.2% accuracy based on validation using the test dataset not included in the original training dataset. In addition, the precision, recall, F-measure, and G-measure were 93.5 - 99.9% for classifying fire and smoke using the test dataset. Ph. D.

Emergency first responders are the great heroes of our day, having to routinely risk their lives for the safety of others. Developing robotic technologies to aid in such emergencies could greatly reduce the risk these individuals must take, even going so far as to eliminate the need to risk one life for another. In this role, humanoid robots are a strong candidate, being able to take advantage of both the human engineered environment in which it will likely operate, but also make use of human engineered tools and equipment as it deals with a disaster relief effort. The work presented here aims to lessen the hurdles that stand in the way through the research and development of new humanoid robot technologies. To be successful in the role of an emergency first responder requires a fantastic array of skills. One of the most fundamental is the ability to just get to the scene. Unfortunately, it is at this level that humanoid robots currently struggle. This research focuses on the complementary development of physical hardware, digital controllers, and trajectory planning necessary to achieve the research goals of improving the locomotion capabilities of a humanoid robot. To improve the physical performance capabilities of the robot, this research will first focus on the interaction between the hip and knee actuators. It is shown that much like the human body, a biped greatly benefits from the use of biarticular actuation. Improvements in efficiency as much as 30% are possible by simply interconnecting the hip roll and knee pitch joints. Balancing and walking controllers are designed to take advantage of the new hardware capabilities and expand the terrain capabilities of bipedal walking robots to uneven and non-stationary ground. A hybrid position/force control based balancing controller stabilizes the robot's COM regardless of the terrain underfoot. In particular two feedback mechanisms are shown to greatly improve the stability of bipedal systems in response to unmodelled dynamics. The hybrid position/force approach is shown through experiments to greatly extend humanoid capabilities to many types of terrain. With robust balancing ensured, walking trajectories are defined using an improved linear inverted pendulum model that incorporates the swing leg dynamics. The proposed method is shown to significantly reduce the control authority (by 50%) required for satisfactory trajectory following. Three parameters are identified which provide for quick manual or numerical solutions to be found to the trajectory problem. The walking and balance controller were operated on four different terrains successfully, strewn plywood, gravel, and high pile synthetic grass. Furthermore, SAFFiR is believed to be the first bipedal robot to ever walk on sand. The hardware enabled force control architecture was very effective at modulating ground reaction torques no matter the ground conditions. This in combination with highly accurate state estimation provided a very stable balance controller on top of which successful walking was demonstrated. Ph. D.

The research presented in this dissertation pertains to the development of a real time SLAM solution that can be performed by a low cost autonomous underwater vehicle equipped with low cost and memory constrained computing resources. The design of a custom rangefinder for underwater applications is presented. The rangefinder makes use of two laser line generators and a camera to measure the unknown distance to objects in an underwater environment. A visual odometry algorithm is introduced that makes use of a downward facing camera to provide our underwater vehicle with localization information. The sensor suite composed of the laser rangefinder, downward facing camera, and a digital compass are verified, using the Extended Kalman Filter based solution to the SLAM problem along with the particle filter based solution known as FastSLAM, to ensure that they provide in- formation that is accurate enough to solve the SLAM problem for out low cost underwater vehicle. Next, an extension of the FastSLAM algorithm is presented that stores the map of the environment using an occupancy grid is introduced. The use of occupancy grids greatly increases the amount of memory required to perform the algorithm so a version of the Fast- SLAM algorithm that stores the occupancy grids using the Haar wavelet representation is presented. Finally, a form of the FastSLAM algorithm is presented that stores the occupancy grid in compressed form to reduce the amount memory required to perform the algorithm. It is shown in experimental results that the same result can be achieved, as that produced by the algorithm that stores the complete occupancy grid, using only 40% of the memory required to store the complete occupancy grid. Ph. D.

This study focuses on the design and implementation of a humanoid robot for disaster response. In particular, this thesis investigates the lower body design in detail with the upper body discussed at a higher level. The Tactical Hazardous Operations Robot (THOR) was designed to compete in the DARPA Robotics Challenge where it needs to complete tasks based on first-responder operations. These tasks, ranging from traversing rough terrain through driving a utility vehicle, suggest a versatile platform in a human sized form factor. A physical experiment of the proposed tasks generated a set of joint range of motions (RoM). Desired limb lengths were determined by comparing existing robots, the test subject in the experiment of proposed tasks, and an average human. Simulations using the desired RoM and limb lengths were used to calculate baseline joint torques. Based on the generated design constraints, THOR is a 34 degree of freedom humanoid that stands 1.78 [m] tall and weighs 65 [kg]. The 12 lower body joints are driven by series elastic linear actuators with multiple joints actuated in parallel. The parallel actuation mimics the human body, where multiple muscles pull on the same joint cooperatively. The legs retain high joint torques throughout their large RoM with some joints achieving torques as high as 289 [Nm]. The upper body uses traditional rotary actuators to drive the waist, arms, and head. The proprioceptive sensor selection was influenced by past experience on humanoid platforms, and perception sensors were selected to match the competition. Master of Science

This paper discusses the design and implementation of a high performance, custom control solution for series elastic actuators (SEA) in a parallel or serial configuration. In many modern robotics applications, controlling actuator output force accurately and with high bandwidth is extremely important. The series elastic actuator has become popular in applications which require precise force control, however currently not many commercial options exist. Commonly, these actuators are custom designed and use electric motors, however most off-the-shelf electric motor drives are not designed for this specific application. In this paper, the hardware and software architecture of a control device designed specifically for force controlled series elastic actuators is described, along with test results on a novel SEA design. Master of Science

The Whole Skin Locomotion robot propels itself using a motion similar to the cytoplasmic streaming exhibited by an amoeba. In the robot there are embedded ring actuators which evert the material of the robot to produce forward motion. The robot benefits from a highly flexible exterior allowing it to squeeze into constricted passageways or collapsed structures. The development of actuators for such a motion is performed by a shape memory alloy composite actuator. Unlike a typical composite model which utilizes a homogenization of fiber and matrix properties our model is developed for line loads produced in individual shape memory alloy wires onto the rod structure. The load vectors are determined in the deformed configuration of the actuator to account for the highly deformed actuator profiles that would be seen in operation. Also the load requirements for such actuators are developed in terms of the constriction forces and functional design limits are established. In addition, a helical spring backbone design is considered and stiffness properties for general helical springs are determined. The contact of spring coils is included in the analysis and a coupled constitutive model is developed for the spring when coils are in contact. The static design of helical springs for use in the actuators is performed and deformation and load restrictions are determined for subsequent design efforts. Ph. D.

Unmanned ground vehicles are increasingly employing a combination of active sensors such as LIDAR with passive sensors like cameras to perform at all levels of perception, which includes detection, recognition and classification. Typical cameras measure the intensity of light at a variety of different wavelengths to classify objects in different areas of an image. A polarimetric camera not only measures intensity of light, but can also determine its state of polarization. The polarization of light is the angle the electric field of the wave of light takes as it travels. A polarimetric camera can identify the state of polarization of the light, which can be used to segment highly polarizing areas in a natural environment, such the surface of water. The polarimetric camera designed and built for this thesis was created with low cost in mind, as commercial polarimetric cameras are very expensive. It uses multiple beam splitters to split incoming light into four machine vision cameras. In front of each machine vision camera is a linear polarizing filter that is set to a specific orientation. Using the data from each camera, the Stokes vector can be calculated on a pixel by pixel basis to determine what areas of the image are more polarized. Test images of various scenes that included running water, standing water, mud, and vehicles showed promise in using polarization data to highlight and identify areas of interest. This data could be used by a UGV to make more informed decisions in an autonomous navigation mode. Master of Science

Both civilian and defense industry rely heavily on robotics which continues to gain a more prominent role. To exemplify, defense strategies in Middle East have relied upon robotic drones and teleoperative assistant robots for mission oriented tasks. These operations have been crucial in saving the lives of soldiers and giving us the edge in mitigating disasters. Future assistive robotics will have direct human interaction and will reside in normal human environments. As the advancement in technology continues to occur, there will be a focus towards eliminating the direct human control and replacing it with higher level autonomy. Further, advancements in electronics and electromechanical components will reduce the cost and makes the assistive robotics accessible to the masses. This thesis focuses on robotic teleoperation technology and the future high level control of assistant robotics. A dexterous 16 degree of freedom hand with bend sensors for precise joint positions was designed, modeled, fabricated and characterized. The design features a unique motor actuation mechanism that was 3D printed to reduce the cost and increase the modularity. The upper body was designed to be biomimetic with dimensions similar to that of a typical six foot tall male. The upper body of the humanoid consists of a 4 degree of freedom shoulder and upper arm with direct feedback at each joint. A theoretical nonlinear switching controller was designed to control these 4 degrees of freedom. The entire system was teleoperative controlled with an Xbox Kinect that tracks the skeletal points of a user and emulates these 3D points to the joints of humanoid upper body. This allows for a direct user control over a robotic assistive upper body with nothing more than a human emulating the desired movements. Master of Science

This dissertation proposes autonomous robotic strategies for urban search and rescue (USAR) which are map-based semi-autonomous robot navigation and fully-autonomous robotic search, tracking, localization and mapping (STLAM) using a team of robots. Since the prerequisite for these solutions is accurate robot localization in the environment, this dissertation first presents a novel grid-based scan-to-map matching technique for accurate simultaneous localization and mapping (SLAM). At every acquisition of a new scan and estimation of the robot pose, the proposed technique corrects the estimation error by matching the new scan to the globally defined grid map. To improve the accuracy of the correction, each grid cell of the map is represented by multiple normal distributions (NDs). The new scan to be matched to the map is also represented by NDs, which achieves the scan-to-map matching by the ND-to-ND matching. In the map-based semi-autonomous robot navigation strategy, a robot placed in an environment creates the map of the environment and sends it to the human operator at a distant location. The human operator then makes decisions based on the map and controls the robot via tele-operation. In case of communication loss, the robot semi-autonomously returns to the home position by inversely tracking its trajectory with additional optimal path planning. In the fully-autonomous robotic solution to USAR, multiple robots communicate one another while operating together as a team. The base station collects information from each robot and assigns tasks to the robots. Unlike the semi-autonomous strategy there is no control from the human operator. To further enhance the efficiency of their cooperation each member of the team specifically works on its own task. A series of numerical and experimental studies were conducted to demonstrate the applicability of the proposed solutions to USAR scenarios. The effectiveness of the scan-to-map matching with the multi-ND representation was confirmed by analyzing the error accumulation and by comparing with the single-ND representation. The applicability of the scan-to-map matching to the real SLAM problem was also verified in three different real environments. The results of the map-based semi-autonomous robot navigation showed the effectiveness of the approach as an immediately usable solution to USAR. The effectiveness of the proposed fully- autonomous solution was first confirmed by two real robots in a real environment. The cooperative performance of the strategy was further investigated using the developed platform- and hardware-in-the-loop simulator. The results showed significant potential as the future solution to USAR. Ph. D.

Geothermal energy can make an important contribution to the U.S. energy portfolio. Production areas require seismic monitoring tools to develop and monitor production capability. This paper describes modifications made to a prototypical seismic tool to implement improvements that were identified during previous tool applications. These modifications included changing the motor required for mechanical coupling the tool to a bore-hole wall. Additionally, development of a closed-loop process control utilized feedback from the contact force between the coupling arm and bore-hole wall. Employing a feedback circuit automates the tool deployment/anchoring process and reduces reliance on the operator at the surface. The tool components were tested under high temperatures and an integrated system tool test demonstrated successful tool operations. Master of Science

This work proposes a series of driver assistance technologies that enable blind persons to safely and independently operate an automobile on standard public roads. Such technology could additionally benefit sighted drivers by augmenting vision with suggestive cues during normal and low-visibility driving conditions. This work presents a non-visual human-computer interface system with passive and adaptive controlling software to realize this type of driver assistance technology. The research and development behind this work was made possible through the Blind Driver Challenge® initiative taken by the National Federation of the Blind. The instructional technologies proposed in this work enable blind drivers to operate an automobile through the provision of steering wheel angle and speed cues to the driver in a non-visual method. This paradigm imposes four principal functionality requirements: Perception, Motion Planning, Reference Transformations, and Communication. The Reference Transformation and Communication requirements are the focus of this work and convert motion planning trajectories into a series of non-visual stimuli that can be communicated to the human driver. This work proposes two separate algorithms to perform the necessary reference transformations described above. The first algorithm, called the Passive Non-Visual Interface Driver, converts the planned trajectory data into a form that can be understood and reliably interacted with by the blind driver. This passive algorithm performs the transformations through a method that is independent of the driver. The second algorithm, called the Adaptive Non-Visual Interface Driver, performs similar trajectory data conversions through methods that adapt to each particular driver. This algorithm uses Model Predictive Control supplemented with Artificial Neural Network driver models to generate non-visual stimuli that are predicted to induce optimal performance from the driver. The driver models are trained online and in real-time with a rapid training approach to continually adapt to changes in the driver's dynamics over time. The communication of calculated non-visual stimuli is subsequently performed through a Non-Visual Interface System proposed by this work. This system is comprised of two non-visual human computer interfaces that communicate driving information through haptic stimuli. The DriveGrip interface is pair of vibro-tactile gloves that communicate steering information through the driver's hands and fingers. The SpeedStrip interface is a vibro-tactile cushion fitted on the driver's seat that communicates speed information through the driver's legs and back. The two interfaces work simultaneously to provide a continuous stream of directions to the driver as he or she navigates the vehicle. Ph. D.

This research effort aims to develop a series of full-sized humanoid robots, and to research a simple but reliable bipedal walking method. Since the debut of Wabot from Waseda University in 1973, several full-sized humanoid robots have been developed around the world that can walk, and run. Although various humanoid robots have successfully demonstrated their capabilities, bipedal walking methods are still one of the main technical challenges that robotics researchers are attempting to solve. It is still challenging because most bipedal walking methods, including ZMP (Zero Moment Point) require not only fast sensor feedback, but also fast and precise control of actuators. For this reason, only a small number of research groups have the ability to create full-sized humanoid robots that can walk and run. However, if we consider this problem from a different standpoint, the development of a full-sized humanoid robot can be simplified as long as the bipedal walking method is easily formulated. Therefore, this research focuses on developing a simple but reliable bipedal walking method. It then presents the designs of two versions of a new class of super lightweight (less than 13 kg), full-sized (taller than 1.4 m) humanoid robots called CHARLI-L (Cognitive Humanoid Autonomous Robot with Learning Intelligence – Lightweight) and CHARLI-2. These robots have unique designs compared to other full- sized humanoid robots. CHARLI-L utilizes spring assisted parallel four-bar linkages with synchronized actuation to achieve the goals of lightweight and low cost. Based on the experience and lesions learned from CHARLI-L, CHARLI-2 uses gear train reduction mechanisms, instead of parallel four-bar linkages, to increase actuation torque at the joints while further reducing weight. Both robots successfully demonstrated untethered bipedal locomotion using an intuitive walking method with sinusoidal foot movement. This walking method is based on the ZMP method. Motion capture tests using six high speed infrared cameras validate the proposed bipedal walking method. Additionally, the total power and energy consumptions during walking are calculated from measured actuator currents. Ph. D.

While haptics, tactile displays, and other topics relating to non-visual user interfaces have been the subject of a variety of research initiatives, little has been done specifically related to those for blind driving. Many automation technologies have been developed for the purpose of assisting and improving the safety of sighted drivers, but to enable a true driving experience without any sense of sight has been an essentially overlooked area of study. Since 2005, the Robotics & Mechanisms Laboratory at Virginia Tech has assumed the task of developing non-visual interfaces for driving through the Blind Driver Challenge®, a project funded by the National Federation of the Blind. The objective here is not to develop a vehicle that will autonomously mobilize blind people, but to develop a vehicle that a blind person can actively and independently operate based on information communicated by non-visual interfaces. This thesis proposes some generalized considerations for the development of non-visual interfaces for driving, using the instructional interfaces developed for the Blind Driver Challenge® as a case study. A model is suggested for the function of blind driving as an open-loop control system, wherein the human is an input/output device. Further, a discussion is presented on the relationship between the bandwidth of information communicated to the driver, the amount of human decision-making involved in blind driving, and the cultivation of driver independence. The considerations proposed here are intended to apply generally to the process of non-visual interface development for driving, enabling efficient concept generation and evaluation. Master of Science

This research effort develops a comprehensive computational framework to support the parametric optimal design of uncertain dynamical systems. Uncertainty comes from various sources, such as: system parameters, initial conditions, sensor and actuator noise, and external forcing. Treatment of uncertainty in design is of paramount practical importance because all real-life systems are affected by it; not accounting for uncertainty may result in poor robustness, sub-optimal performance and higher manufacturing costs. Contemporary methods for the quantification of uncertainty in dynamical systems are computationally intensive which, so far, have made a robust design optimization methodology prohibitive. Some existing algorithms address uncertainty in sensors and actuators during an optimal design; however, a comprehensive design framework that can treat all kinds of uncertainty with diverse distribution characteristics in a unified way is currently unavailable. The computational framework uses Generalized Polynomial Chaos methodology to quantify the effects of various sources of uncertainty found in dynamical systems; a Least-Squares Collocation Method is used to solve the corresponding uncertain differential equations. This technique is significantly faster computationally than traditional sampling methods and makes the construction of a parametric optimal design framework for uncertain systems feasible. The novel framework allows to directly treat uncertainty in the parametric optimal design process. Specifically, the following design problems are addressed: motion planning of fully-actuated and under-actuated systems; multi-objective robust design optimization; and optimal uncertainty apportionment concurrently with robust design optimization. The framework advances the state-of-the-art and enables engineers to produce more robust and optimally performing designs at an optimal manufacturing cost. Ph. D.

Electro-active polymers (EAPs) have emerged as a new class of active materials, which produce large deformations in response to an electric stimulus. EAPs have attractive characteristics of being lightweight, inexpensive, stretchable, and flexible. Additionally, EAPs are conformable, and their properties can be tailored to satisfy a broad range of requirements. These advantages have enabled many target applications in actuation and sensing. A general constitutive formulation for isotropic and anisotropic electro-active materials is developed using continuum mechanics framework and invariant theory. Based on the constitutive law, electromechanical stability of the electro-elastic materials is investigated using convexity and polyconvexity conditions. Implementation of the electro-active material model into a commercial finite element software (ABAQUS 6.9.1, PAWTUCKET, RI, USA) is presented. Several boundary and initial value problems are solved to investigate the actuation and sensing response of isotropic and anisotropic dielectric elastomers (DEs) subject to combined mechanical and electrical loads. The numerical response is compared with experimental results to validate the theoretical model. For the constitutive formulation of the electro-elastic materials, invariants for the coupling between two families of electro-active fibers (or particles) and the applied electric field are introduced. The effect of the orientation of the electro-active fibers and the electric field on the electromechanical coupling is investigated under equibiaxial extension. Advantage of the constitutive formulation derived in this research is that the electromechanical coupling can be illustrated easily by choosing invariants for the deformation gradient tensor, the electro-active fibers, and the electric field. For the electromechanical stability, it is shown that the stability can be controlled by tuning the material properties and the orientation of the electro-active fibers. The electromechanical stability condition is useful to build a stable free energy function and prevent the instabilities (wrinkling and electric breakdown) for the electro-elastic materials. The invariant-based constitutive formulation for the electro-elastic materials including the isotropic and anisotropic DEs is implemented into a user subroutine (UMAT in ABAQUS: user defined material) by using multiplicative decomposition of the deformation gradient and the applicability of the UMAT is shown by simulating a complicated electromechanical coupling problem in ABAQUS/CAE. Additionally, the static and dynamic sensing and actuation response of tubular DE transducers (silicone and polyacrylate materials) with respect to combined electrical and mechanical stimuli is obtained experimentally. It is shown that the silicone samples have better dynamic and static sensing characteristics than the polyacrylate. The theoretical modeling accords well with the experimental results. Ph. D.

Telemanipulators allow a user to interact with a potentially dangerous environment remotely. Deploying a robot arm from a UAV would allow an operator to reach farther and quicker than he or she would with a ground robotics system alone. This thesis will discuss the design and fabrication of a compact, light, 3 degree of freedom robot arm using common off the shelf products and machined components that in combination can pick up half pound samples and has a reach of 260 mm. Also addressed is making the telemanipulator interface easier to use. One of the challenges in using a robot arm with a single camera in a beyond line-of-sight scenario is the difficulty of interacting with the environment because of a loss of depth information. This lack of information can be remedied with additional sensors. Once depth to an object of interest is known, the sampler can automatically pick up objects of interest. The manipulator arm will be used in conjunction with systems developed by the Unmanned Systems Laboratory at Virginia Tech. This group is developing a unmanned ground vehicle to be carried in the payload pod of a unmanned aerial vehicle. The robot's ultimate objective is to collect shrapnel and bomb material from potentially dangerous environments. Master of Science

A future limitation of autonomous ground vehicle technology is the inability of current algorithmic techniques to successfully predict the allowable dynamic operating ranges of unmanned ground vehicles. A further difficulty presented by real vehicles is that the payloads may and probably will change with unpredictably time as will the terrain on which it is expected to operate. To address this limitation, a methodology has been developed to generate real-time estimations of a vehicle's instantaneous Maneuvering Manifold. This approach uses force-moment method techniques to create an adaptive, parameterized vehicle model. A technique is developed for estimation of vehicle load state using internal sensors combined with low-magnitude maneuvers. An unscented Kalman filter based estimator is then used to estimate tire forces for use in determining the ground/tire coefficient of friction. Probabilistic techniques are then combined with a combined-slip pneumatic trail based estimator to estimate the coefficient of friction in real-time. This data is then combined to map out the instantaneous maneuvering manifold while applying techniques to account for dynamic rollover and stability limitations. The algorithms are implemented in MATLAB, simulated against TruckSim models, and results are shown to demonstrate the validity of the techniques. The developed methodology is shown to be a novel approach that is capable of addressing the problem of successfully estimating the available maneuvering manifold for autonomous ground vehicles. Ph. D.

This dissertation presents the kinematics study on two cases of parallel locomotion mechanisms. A parallel locomotion mechanism can be defined as "a mechanism with parallel configuration and discrete contact with respect to the ground which renders a platform the ability to move". The first case is a tripedal robot and the second case is an actuated spoke wheel robot. The kinematics study on these two mobile robots mainly includes mobility, inverse and forward kinematics, instantaneous kinematics, singularity and so on. The tripedal robot STriDER (Self-excited Tripedal Dynamic Experimental Robot) is expected to walk utilizing its built-in passive dynamics, but in its triple stance phase, the kinematic configuration of the robot behaves like an in-parallel manipulator. The locomotion of this novel walking robot and its unique tripedal gait are discussed, followed by the definitions of its coordinate frames. Geometric methods are adopted for the forward and inverse displacement analysis in its triple stance phase. Simulations are presented to validate both the inverse and the forward displacement solutions. The instantaneous kinematics and singularity analysis are developed respectively. Based on the screw theory, the Jacobian matrices are assembled. Using Grassmann Line Geometry, each row of the Jacobian matrices is interpreted as a line in 3D space and the analytical conditions of the linear dependency cases are identified, which corresponds to the forward singular configurations of the robot. The actuated spoke wheel robot IMPASS (Intelligent Mobility Platform with Active Spoke System) is investigated as the second case. It is revealed that this robot has multiple modes of locomotion on the ground and it is able to change its topology by changing the contact scheme of its spokes with the ground. This robot is treated as a mechanism with variable topologies and Modified Grübler-Kutzbach criterion and Grassmann Line Geometry are adopted to identify the degrees of freedom (DOF) for each case of its topological structures. The characteristic DOF are then verified through the testing on the robot prototype. The forward and inverse kinematics is investigated for two cases of its topologies. In order to improve the computation efficiency of the inverse kinematics formulation, virtual serial manipulator models are constructed. The effectiveness of the virtual serial manipulator models has been validated with numerical simulations. In conclusion, kinematics analyses have been successfully performed on the two parallel locomotion mechanisms. The results are utilized to control the robots' motions in specific configurations. The foundation has been laid for the future development of the robot prototypes and the future research on dynamics, control, intelligence and so on. Ph. D.

Bipedal locomotion in humanoid robots is a very challenging problem within the field of robot locomotion. In this thesis, we propose and demonstrate an omni-directional walking engine that achieves stable walking using feedback from an inertial measurement unit. Our walking engine generates gaits for which the zero moment point is on the center of the supporting foot. The mechanical structure of CHARLI-L, a humanoid robot used as our test platform in this thesis, is first introduced by describing the inverse kinematics of its legs. The principles of the omni-directional gait generator that creates walking motions and overcomes the robot's mechanical deficiencies is discussed. We develop and implement two kinds of feedback controllers; one is the gait feedback controller and the other is the joint feedback controller. Both feedback controllers use proportional-derivative of the angle of the pelvis from an inertial measurement unit. The results of the experiments are presented the efficacy of our proposed walking engine. Master of Science

Mimicking facial structures for a robotic head requires integration of multiple structural and mechanical parameters, design, synthesis and control of muscle actuation, architecture of the linkages between actuation points within skin, and implementation of the deformation matrix with respect to global skull coordinates. In this dissertation, humanoid faces were designed and fabricated to investigate all the parameters mentioned above. A prototype face and neck was developed using servo motors and extensively characterized. In this prototype, a neck mechanism was designed using a four bar mechanism to achieve nodding and turning motions. The modular neck prototype simplifies the assembly and statically in equilibrium and hence demands less torque from the cost-effective RC servo motor. The mechanism was critically investigated for dynamic performance and it was found out that RC servo based robotic head requires a PD external controller to overcome inherent overshoot. The servo based robotic head was analyzed for design and control of anchor, architecture of linkages between actuation points within skin, and deformation matrix with respect to global coordinate for creating specific expressions. A functional relationship between deformation vector of facial control points and actuator parameter, skin elasticity and angular position of actuator was derived. The developed analysis method is applicable to any rotary actuator technology utilized for facial expressions and takes into account the skin stiffness. The artificial skin materials for facial expression were synthesized using platinum-cured silicone elastomeric material (Reynolds Advanced Materials Inc.) with base consisting of mainly polyorganosiloxanes, amorphous silica and platinum-siloxane complex compounds. Systematic incorporation of porosity in this material was found to lower the force required to deform the skin in the axial direction. The performance of the servo motor based face was quite realistic but it suffers from the drawback of large power consumption, bulky, heavy, and limited functionality. Thus, significant effort was made in developing a Biometal fiber and Flexinol shape memory alloy actuator (SMA) based biped mountable baby head facial structure which resembles the form and functionality of a human being. SMAs were embedded inside a skull and connected to elastomeric skin at control points. An engineered architecture of skull was fabricated that incorporates all the muscles with their 35 routine pulleys, two fire wire CMOS cameras that serve as eyes, and a battery powered microcontroller base driving circuit within the total dimensions of 140 mm x 90 mm x 110 mm. The driving circuit was designed such that it can be easily integrated with biped and processed in real-time. The humanoid face with 12DOF was mounted on the body of DARwIn (Dynamic Anthropomorphic Robot with Intelligence) robot which has 21 DOF resulting in a total of 33 DOF system. Characterization results on the face and associated design issues are described that provide pathways for developing human-like facial anatomy. Numerical simulation using Simulink was conducted to assess the performance of a prototypic robotic face mainly focusing on jaw movement. A graphical method “Graphical Facial Expression Analysis and Design (GFEAD)” was developed that can be used to allocate the sinking points on robotic head. The method assumes that the origin of the action units are known prior and the underlying criterion in the design of faces being deformation of a soft elastomeric skin through tension in anchoring wires attached on one end to the sinking point and on the other to the actuator. Experimental characterization on a prototyping humanoid face was performed to validate the model and demonstrate the applicability on a generic platform. During characterization of the SMA based face, it was found that the currently available artificial muscle technologies do not meet the entire requirement for being embedded in the skin and provide the required strain rate, maximum strain, blocking force, response time and energy density. Thus an effort was made to develop conducting polymer based artificial muscles which can meet the metrics of human muscle. Composite stripe and zigzag actuators consisting of a sandwich structure polypyrrole /poly(vinylidene difluoride) (PPy/PVDF) were synthesized using potentiodynamic film growth on gold electrodes. The synthesis was done from an aqueous solution containing tetrabutylammonium Perchlorate (TBAP) and pyrrole by polymerization at room temperature. For depositing thin PPy films and thereby minimizing the response time, an experimental optimization of the deposition conditions was performed. The number of current-potential (potentiodynamic) growth cycles and the thickness of the deposited PPy film were highly correlated in the initial stages of polymer film growth. Strip actuator of size 11 x 5 mm2 with 63μM exhibited a deflection of 3mm under 1V DC voltage and 2mm deflection under 8V AC voltage at 0.5 Hz. It was found that three-segment zigzag actuator of segment length 15x2.5mm and thickness 63μM amplifies the displacement by 1.5 times. A study was also conducted on the synthesis and characterization of thick and thin film polypyrrole (PPy) – metal composite actuators. The fabrication method consisted of three steps based upon the approach proposed by Ding et al.: (i) winding the conductive spiral structure around the platinum (Pt)-wire core, (ii) deposition of PPy film on the Pt-wire core, and (iii) removal of the Pt-wire core. This approach yielded good performance from the synthesized actuators, but was complex to implement due to the difficulty in implementing the third step. To overcome the problem of mechanical damage occurring during withdrawal of Pt-wire, the core was replaced with a dispensable gold coated polylactide fiber that could be dissolved at the end of deposition step. Experimental results indicate that thin film actuators perform better in terms of response time and blocking force. A unique muscle-like structure with smoothly varying cross-section was grown by combining layer by layer deposition with changes in position and orientation of the counter electrode in reference to the working electrode. Synthesis of polypyrrole–metal coil was conducted in aqueous solution containing 0.25 M Pyrrole, 0.10 M TBAP and 0.50 M KCl. The actuator consisted of a single layer of platinum winding on a core substrate. Electrochemical characterization for free strain and blocking stress was conducted 0.1 M TBAP solution and a 6% free strain was obtained at an applied potential of 6V DC after 80 s stimulation time. The blocking stress 18 kPa was estimated by extrapolating the strain magnitude on stress-strain diagram. For axial type actuator with coil winding, a generalized governing equation for the electrochemical stress generated from polypyrrole–metal coil which accommodates the effect of magnetic field due to winding was proposed and numerically studied. It was considered as insightful modeling. Ph. D.

Networked, multi-sensor array systems have proven to be advantageous in the sensor world. A large amount of research has been conducted with these systems, with a main interest in data fusion. Intelligently processing the large amounts of data collected by these systems is required in order to fully utilize the benefits of a multi-sensor array system. A robust but flexible simulation environment would provide a platform for accurately comparing current and future data fusion theories. This thesis proposes a simulator model for testing fusion theories for these acoustic multi-sensor networks. An iterative, lossless data fusion algorithm was presented as the model for simulation development. The arrangement and orientation of objects in the simulation environment, as well as most other system parameters are defined by the user before the simulation runs. The sensor data, including noise, is generated at the appropriate time delay and propagation loss before being processed by a delay and sum beamformer and a matched filter. The resulting range-Doppler maps are modified to probability density functions, and translated to a single point of reference. The data is then combined into a single world model. An iterative process is used to filter out false targets and amplify true target detections. Data is fused from each multi-sensor array and from each simulation run. Target amplitudes are gained if they are present in all combined world models, and are otherwise reduced. This thesis presents the results of the fusion algorithm used, including multiple iterations, to prove the algorithms effectiveness. Master of Science

An infinitely variable transmission (IVT) is a transmission that can smoothly and continuously vary the speed ratio between an input and output from zero to some other positive or negative ratio; they are a subset of continuously variable transmissions (CVTs), which themselves do not have the ability to produce a zero gear ratio. In this thesis, the operation, analysis, and development of a novel, highly configurable, Cam-based Infinitely Variable Transmission of the ratcheting drive type is presented. There are several categories of CVTs in existence today, including traction, belt, and ratcheting types. Drives of these types, their attributes, and associated design challenges are discussed to frame the development of the Cam-based IVT. The operation of this transmission is kinematically similar to a planetary gearset, and therefore, its operation is described with that in mind including a description of the six major components of the transmission, those being the cam, followers, carriers, planet gears, sun gears, and one way clutches. The kinematic equation describing its motion is derived based on the similarities it shares with a planetary gearset. Additionally, the equations for the cam design are developed here as the operation of the CVT is highly dependent on the shape of the cam. There are six simple inversions of this device and each inversion has special characteristics and limitations, for example, the available gear range. A method was developed to select the most suitable inversion, gearing, and follower velocity for a given application. The contact stress between the rollers and cam is the limiting stress within the transmission. A parametric study is used to quantify the relationship between this stress and the transmission parameters. Based off those results, two optimization strategies and their results are discussed. The first is an iterative brute force type numerical search and the second is a genetic algorithm. The optimization results are shown to be similar and successfully reduced the contact stress by 40%. To further improve the transmission performance, several mechanisms were developed for this unique transmission. These include a compact and lightweight differential mechanism based on a cord and pulley system to reduce the contact force on the rollers. In addition, a unique external/inverted cam topology was developed to improve the contact geometry between the rollers and said cam. A prototype was built based on both the optimization strategies and these mechanisms and is described within. Finally, a Prony brake dynamometer with cradled motor was constructed to test the transmission; the results of those tests show the Cam-based IVT to be 93% efficient at low input torque levels. Master of Science

In the past few years, the price of petroleum based fuels, especially vehicle fuels such as gasoline and diesel, has been increasing at a significant rate. Consequently, there is much more consumer interest related to reducing fuel consumption for conventional vehicles and hybrid electric vehicles (HEVs) than in the past. The goal of many competitions and challenges held in North America and Europe is to achieve extremely low fuel consumption. A possible strategy to reduce fuel consumption is to use the vehicle's fuel converter such as an engine to accelerate the vehicle to a high speed and coast to a lower speed with the engine off. This method will reduce fuel flow to zero during the coast phase. Also, the vehicle uses higher power engine load to accelerate to the upper vehicle speed in a limited time, thus increasing the engine brake thermal efficiency. This strategy is known as "pulse and glide" or "burn and coast" in some references. In this study, the "pulse and glide" (PnG) method is first applied to a conventional vehicle to quantify the fuel consumption benefits when compared to steady speed conditions over the same distance. After that, an HEV is used as well to investigate if a hybrid system can further reduce fuel consumption with the proposed strategy. Note that the HEV used in this study has the advantage that the engine can be automatically shut off below a certain speed (~40 mph) at low loads, however a driver must shut off the engine manually in a conventional vehicle to apply this driving strategy. In this document, three preliminary results of the PnG driving strategy are presented; (1) improved fuel economy for a conventional vehicle from a simple spread sheet model, (2) improved fuel economy for an HEV from a dynamic vehicle simulation model (the Powertrain Analysis Toolkit (PSAT)) and (3) improved fuel economy for an HEV from vehicle testing at Argonne National Laboratory (ANL), all compared to steady speed conditions. The preliminary results show that the impact of engine load and kinetic energy stored in vehicle inertia is significant for fuel consumption using a PnG driving strategy compared to steady speed driving at the same average speed case. Especially, fuel economy can be improved at low speed range and higher acceleration because the aerodynamic drag force is smaller at low speed and the engine is running in a more efficient region for a short period of time respectively. In the last section, proposed directions of research are addressed based on the preliminary results. Ph. D.

For realistic predictions of vehicle performance in off-road conditions, it is critical to incorporate in the simulation accurate representations of the variability of the terrain profile. It is not practically feasible to measure the terrain at a sufficiently large number of points, or, if measured, to use such data directly in the simulation. Dedicated modeling techniques and computational methods that realistically and efficiently simulate off-road operating conditions are thus necessary. Many studies have been recently conducted to identify effective and appropriate ways to reduce experimental data in order to preserve only essential information needed to re-create the main terrain characteristics, for future use. This thesis focuses on modeling terrain profiles using the finite difference approach for solving linear second-order stochastic partial differential equations. We currently use this approach to model non-stationary terrain profiles in two dimensions (i.e., surface maps). Certain assumptions are made for the values of the model coefficients to obtain the terrain profile through the fast computational approach described, while preserving the stochastic properties of the original terrain topology. The technique developed is illustrated to recreate the stochastic properties of a sample of terrain profile measured experimentally. To further analyze off-road conditions, stochastic soil properties are incorporated into the terrain topology. Soil models can be developed empirically by measuring soil data at several points, or they can be created by using mathematical relations such as the Bekker's pressure-sinkage equation for homogeneous soils. In this thesis, based on a previously developed stochastic soil model, the polynomial chaos method is incorporated in the soil model. In a virtual proving ground, the wheel and soil interaction has to be simulated in order to analyze vehicle maneuverability over different soil types. Simulations have been created on a surface map for different case studies: stepping with a rigid plate, rigid wheel and flexible wheel, and rolling of a rigid wheel and flexible wheel. These case studies had various combinations of stochastic or deterministic terrain profile, stochastic or deterministic soil model, and an object to run across the surface (e.g., deterministic terrain profile, stochastic soil model, rolling rigid wheel). This thesis develops a comprehensive terrain and soil simulation environment for off-road mobility studies. Moreover, the technique developed to simulate stochastic terrain profile can be employed to simulate other stochastic systems modeled by PDEs. Master of Science

Mimicking human motion with a humanoid robot can prove to be useful for studying gaits, designing better prostheses, or assisting the elderly or disabled. Directly mimicking and implementing a motion of a human on a humanoid robot may not be successful because of the different dynamic characteristics between them, which may cause the robot to fall down due to instability. Using the Zero Moment Point as the stability criteria, this work proposes an Analytical Motion Filter (AMF), which stabilizes a reference motion that can come from human motion capture data, gait synthesis using kinematics, or animation software, while satisfying common constraints. In order to determine how the AMF stabilized a motion, the different kinds of instabilities were identified and classified when examining the reference motions. The different cases of instability gave more insight as to why a particular motion was unstable: the motion was too fast, too slow, or inherently unstable. In order to stabilize the gait two primary methods were utilized: time and spatial scaling. Spatial scaling scaled the COM trajectory down towards a known stable trajectory. Time scaling worked similarly by changing the speed of the motion, but was limited in effectiveness based on the types of instabilities in the motion and the coupling of the spatial directions. Other constraints applied to the AMF and combinations of the different methods produced interesting results that gave more insight into the stability of the gait. The AMF was tested using both simulations and physical experiments using the DARwIn miniature humanoid robot developed by RoMeLa at Virginia Tech as the test platform. The simulations proved successful and provided more insight to understanding instabilities that can occur for different gait generation methods. The physical experiments worked well for non-walking motions, but because of insufficient controllability in the joint actuators of the humanoid robot used for the experiment, the high loads during walking motions prevented them from proper testing. The algorithms used in this work could also be expanded to legged robots or entirely different platforms that depend on stability and can use the ZMP as a stability criterion. One of the primary contributions of this work was showing that an entire reference motion could be stabilized using a single set of closed form solutions and equations. Previous work by others considered optimization functions and numeric schemes to stabilize all or a portion of a gait. Instead, the Analytical Motion Filter gives a direct relationship between the input reference motion and the resulting filtered output motion. Ph. D.

Each year, falls from elevated structures, like scaffolding, kill or seriously injure over a thousand construction workers (Bureau of Labor Statistics, 2007). To prevent such falls, the development of a robotic system is proposed that can climb and navigate on the complex structures, performing hazardous inspection and maintenance in place of humans. In this work, a serpentine robotic system is developed that will be able to climb pole-like structures, such as scaffolding and trusses, commonly found on work sites. Serpentine robots have been proven to be effective at traversing unstructured terrains and manipulating complex objects. The work presented in this thesis adds a new method of mobility for serpentine robots, specifically those with actuated universal joint structures. Movement is produced by inducing a wobbling motion between adjacent modules through oscillatory motions in the actuated axis of the universal joint. Through the frictional interactions between the modules of the serpentine and the surface of the pole, the wobbling motion lets the serpentine effectively roll up the pole's surface. This work investigates theoretical and experimental results for a serpentine robot climbing a pole structure. It discusses the structure and design parameters of the robot and develops relationships between them. These geometric and performance-based relationships are then used to create a design space that provides a guide for choosing a combination of module dimensions for a desired set of performance parameters. From this, case studies are shown which give examples of how the design space can be used for several different applications. Based on the design space procedure, a serpentine robot, HyDRAS (Hyper-Redundant Discrete Robotic Articulated Serpentine) was designed and built. The robot was used to prove the validity of the design space procedure and to validate the climbing motion algorithms. Several tests were performed with HyDRAS that showed the practicality of the helical rolling motion, as well as the feasibility of serpentine pole climbing. Observations and discussion based on the experiments are given, along with the plans for future work involving pole-climbing serpentine robots. Master of Science

Mechanical systems always operate under some degree of uncertainty, which can be due to the inherent properties of the system parameters, to random inputs or external excitations, to poorly known parameters in the interface between different systems, or to inadequate knowledge of the dynamic process. Also, mechanical systems are large and highly nonlinear, while the magnitude of uncertainties may be very large. This dissertation addresses the critical need for understanding of the stochastic nature of mechanical system, especially vehicle and terramechanics systems, and need for developing efficient computational tools to model mechanical systems in the presence of parametric and external uncertainty. This dissertation investigates the influence of parametric and external uncertainties on vehicle dynamics and terramechanics. The uncertainties studied include parametric uncertainties, stochastic external excitations, and random variables between vehicle-terrain and vehicle-soil/snow interface. The methodology developed has been illustrated on a stochastic vehicle-terrain interaction model, a stochastic vehicle-soil interaction model, two stochastic tire-snow interaction models, and two stochastic tire-force relations. The uncertainties are quantified and propagated through vehicle and terramechanics systems using a polynomial chaos approach. Algorithms which can predict the geometry of the contact patch and the interfacial forces and torques on the vehicle-soil interfaces are developed. All stochastic models and algorithms are simulated for various scenarios and maneuvers. Numerical results are analyzed from the computational effort point of view, or from the angle of vehicle dynamics and terramechanics, and provide a deeper understanding of the evolution of stochastic vehicle and terramechanics systems. They can also be used in guiding vehicle design and development. This dissertation represents a pioneer study on stochastic vehicle dynamics and terramechanics. Moreover, the methodology developed is not limited to such systems. Any mechanical system with uncertainties can be treated using the polynomial chaos approach presented, considering their specific characteristics. Ph. D.

Gait is the method of human locomotion using limbs. Recently, the analysis of human motion, specifically human gait, has received a large amount of research attention. Human gait can contain a wide variety of information that can be used in biometrics, disease diagnosis, injury rehabilitation, and load determination. In this dissertation, the development of a model-based gait analysis technique to classify external loads is presented. Specifically, the effects of external loads on gait are quantified and these effects are then used to classify whether an individual gait pattern is the result of carrying an external load or not. First of all, the reliability of using continuous relative phase as a metric to determine loading condition is quantified by intra-class correlation coefficients (ICC) and the number of required trials is computed. The ICC(2, 1) values showed moderate reliability and 3 trials are sufficient to determine lower body kinematics under two external load conditions. Then, the work was conducted to provide the baseline separability of load carriage conditions into loaded and unloaded categories using several lower body kinematic parameters. Satisfactory classification of subjects into the correct loading condition was achieved by resorting to linear discriminant analysis (LDA). The baseline performance from 4 subjects who were not included in training data sets shows that the use of LDA provides an 88.9% correct classification over two loaded and unloaded walking conditions. Extra weights, however, can be in the form of an external load carried by an individual or excessive body weight carried by an overweight individual. The study now attempts to define the differences in lower body gait patterns caused by either external load carriage, excessive body weight, or a combination of both. It was found significant gait differences due to external load carriage and excessive body weight. Principal Component Analysis (PCA) was also used to analyze the lower body gait patterns for four loading conditions: normal weight unloaded, normal weight loaded, overweight unloaded and overweight loaded. PCA has been shown to be a powerful tool for analyzing complex gait data. In this analysis, it is shown that in order to quantify the effects of external loads for both normal weight and overweight subjects, only two principal components (PCs) are needed. The results in this dissertation suggest that there are gait pattern changes due to external loads, and LDA could be applied successfully to classify the gait patterns with an unknown load condition. Both load carriage and excessive body weight affect lower body kinematics, but it is proved that they are not the same loading conditions. Methods in the current work also give a potential for new medical and clinical ways of investigating gait effects in osteoarthritis patients and/or obese people. Ph. D.

Cerebral palsy is an occurrence in which the nerves and muscles if the body may function properly, but there is damage to the brain that causes it to transmit incorrect electrical impulses to the muscles including both too many and too few signals. Without the correct cohesive electrical impulses to balance the opposing muscles of a joint, normal everyday tasks that most of us take for granted become very difficult to learn and perform. As exoskeletons become more advanced and practical, their applications have a lot of room for growth. Cerebral Palsy is one portion of the medical field that can benefit from the development of exoskeletons. As demonstrated with modern rehabilitation techniques, the application of an exoskeleton has the possibility of making the learning process and performance of many tasks easier and faster for both the patient as well as the doctor working with them. However, in order to appropriately apply the technology to the need, many changes in both the controls and the actual physical design of current devices need to be addressed. An exoskeleton for the purpose of helping cerebral palsy patients learn to walk is not limited to one specific form depending on the complexity of the tasks it is desired to assist with. However, there are a couple needs of this type of exoskeleton that are absolutely necessary. The size of the exoskeleton must be designed around the size of a child and not an adult. If the individual is learning to walk from the very beginning, the controls of the device will need to initially be able to take complete control over the individual's limbs to exercise the motions of walking. With the nature of an exoskeleton controlling the limbs of a person instead of simply assisting with current movements, the physical attachments of the exoskeleton must be improved from current designs in order to make movements of the exoskeleton and the body more parallel. Other features such as different muscle sensing techniques may also improve performance, but are not required. An exoskeleton that can help cerebral palsy patients learn to walk can also be applied to many other rehabilitation needs. Master of Science

IMPASS is a novel spoke-wheel robot invented by researchers at the Robotics and Mechanisms Lab (RoMeLa) at Virginia Tech. The robot is driven by a rimless spoke wheel which can alter the length of any given spoke in the hub. This form of novel locomotion combines the efficiency of a wheeled robot and the mobility of a legged robot, arriving at a very practical mobility platform. A highly mobile robot such as IMPASS could prove very valuable in applications where the terrain is complex and dangerous, such as search and rescue, reconnaissance, or anti-terror response. A prototype has been constructed that effectively demonstrates the actuated spoke wheel concept using two wheels containing six spokes each. Manually controlling the motion of two wheels and twelve spokes would be a daunting task for any operator. Due to this inherent complexity, automated motion control is a necessity for the IMPASS platform. The work presented here will discuss two different approaches to the motion planning problem for the two-dimensional sagittal plane. The first approach is deliberative in nature and depends on fairly accurate terrain sensing. The motion planning first decides on a set of contact points based on obstacle configurations and a Lagrangian interpolation of the terrain. A lower level motion planning component then executes the movements that guide the spoke ends to the contact points. The second motion planning approach is reactive in nature. Proprioceptive and tactile sensors are used to determine the robot's pose and immediate surroundings. These sensors directly affect the motion profile of the robot. The reactive approach follows much simpler logic, which theoretically will make it more robust. Motion planning strategies were tested in simulation and on the IMPASS prototype. Both strategies proved to be well suited for different applications. The deliberative control was very successful in a structured environment, whereas the reactive control was able to cross a wider variety of terrain. The results from the testing also provided some insight into variables introduced by the hardware. Future improvements to the motion planning control include accounting for these variables in the hardware and eventually developing three-dimensional motion planning algorithms based on the lessons learned from the two-dimension case. Master of Science

This thesis addresses two important issues when operating the novel three legged mobile robot STriDER (Self-excited Tripedal Dynamic Experimental Robot); how to stand up after falling down while minimizing the motor torques at the joints and considerations for gait planning. STriDER uses a unique tripedal gait to walk with high energy efficiency and has the ability to change directions. In the first version of STriDER, the concept of passive dynamic locomotion was emphasized; however, for the new version, all joints are actively controlled for robustness. The robot is inherently stable when all three feet are on the ground due to its tripod stance, but it can still fall down if it trips while taking a step or if unexpected external forces act on it. The unique structure of STriDER makes the simple task of standing up challenging for a number of reasons; the high height of the robot and long limbs require high torque at the actuators due to its large moment arms; the joint configuration and length of the limbs limit the workspace where the feet can be placed on the ground for support; the compact design of the joints allows limited joint actuation motor output torque; three limbs do not allow extra support and stability in the process of standing up. This creates a unique problem and requires novel strategies to make STriDER stand up. This thesis examines five standing up strategies unique to STriDER: three feet pushup, two feet pushup, one foot pushup, spiral pushup, and feet slipping pushup. Each strategy was analyzed and evaluated considering constraints such as static stability, friction at the feet, kinematic configuration and joint motor torque limits to determine optimal design and operation parameters. Using the findings from the analysis, experiments were conducted for all five standing up strategies to determine the most efficient standing up strategy for a given prototype using the same design and operation parameters for each method. Also, a literature review was conducted for human standing from a chair and human pushup exercises and the conclusions were compared to the analysis presented in this thesis. Many factors contribute to the development of STriDER's gait. Several considerations for gait planning as the robot takes a step are investigated, including: stability, dynamics, the body's maximum and minimum allowable heights, the swing legs foot clearance to the ground, and the range of the subsequent swing foot contact positions. A static stability margin was also developed to asses the stability of STriDER. This work will lay the foundation for future gait generation research for STriDER. Additionally, guidelines for future work on single step gait generation based on kinematics and dynamics are discussed. The findings presented will advance the capabilities and adaptability of the novel robot STriDER. By studying standing up strategies and gait planning issues, the most efficient control methods can be implement for standing up and preparing to take a step and lay out the foundations for future research and development on STriDER. Master of Science

The kinematic analysis of an articulated twin body, four-wheel, robotic vehicle is presented. Polaris, a research platform and contending robotic vehicle in the Intelligent Ground Vehicle Competition (IGVC) at Virginia Tech, was redesigned in 2006 to improve the mobility of the vehicle by incorporating an innovative four-bar linkage that connects the two bodies. The new linkage design minimizes vehicle off-tracking by allowing the rear wheels to closely track the path of the front wheels. This thesis will outline the theoretical kinematic model of the four-bar linkage as applied to a twin-bodied, differentially driven vehicle. The kinematic model is validated through computer simulation as well as experimentation on a fully operational robotic vehicle. The kinematic model presented here outlines the foundations for an autonomous, four-wheel drive, multi-body control system and opens avenues for dynamically controlling the tracking of the vehicle's rear body with an actuated linkage configuration. Master of Science

Development of unmanned vehicles will increase as the need to save lives rises. In both military and civilian applications, humans can be taken out of the loop through the implementation of safe and intelligent autonomous vehicles. Although hardware and software development continue to play a large role in the autonomous vehicle industry, validation of these systems will always be necessary. The ability to test these vehicles thoroughly and efficiently will ensure their proper and flawless operation. On November 3, 2007 the Defense Advanced Research Projects Agency held the Urban Challenge to drive the development of autonomous ground vehicles for military use. This event required vehicles built by teams across the world to autonomously navigate a 60 mile course in an urban environment in less than 6 hours. This thesis addresses the testing aspect of autonomous ground vehicles that exhibit the advanced behaviors necessary for operating in such an event. Specifically, the experiences of Team Victor Tango and other Urban Challenge teams are covered in detail. Testing facilities, safety measures, procedures, and validation methods utilized by these teams provide valuable information on the development of their vehicles. Combining all these aspects results in a proposed testing strategy for autonomous ground vehicles. Master of Science

Position in the environment is essential in any autonomous system. As increased accuracy is required, the costs escalate accordingly. This paper presents a simple way to systematically integrate sensory data to provide a drivable and accurate position solution at a low cost. The data fusion is handled by a Kalman filter tracking five states and an undetermined number of asynchronous measurements. This implementation allows the user to define additional adjustments to improve the overall behavior of the filter. The filter is tested using a suite of inexpensive sensors and then compared to a differential GPS position. The output of the filter is indeed a drivable solution that tracks the reference position remarkably well. This approach takes advantage of the short-term accuracy of odometry measurements and the long-term fix of a GPS unit. A maximum error of two meters of deviation from the reference is shown for a complex path over two minutes and 100 meters long. Master of Science

Research in mobile robotics, unmanned systems, and autonomous man-portable vehicles has grown rapidly over the last decade. This push has taken the problems of robot cognition and behavioral control out of the lab and into the field. Two good examples of this are the DARPA Urban Challenge autonomous vehicle race and the RoboCup robot soccer competition. In these challenges, a mobile robot must be capable of completing complex, sophisticated tasks in a dynamic, partially observable and unpredictable environment. Such conditions necessitate a behavioral programming approach capable of performing high-level action selection in the presence of multiple goals of dynamically changing importance, and noisy, incomplete perception data. In this thesis, an approach to behavioral programming is presented that provides the designer with an intuitive method for building contextual intelligence while preserving the qualities of emergent behavior present in traditional behavior-based programming. This is done by using a modified hierarchical state machine for behavior arbitration in sequence with a command fusion mechanism for cooperative and competitive control. The presented approach is analyzed with respect to portability across platforms, missions, and functional requirements. Specifically, two landmark case-studies, the DARPA Urban Challenge and the International RoboCup Competition are examined. Master of Science

For their inherent stability and simple dynamics of motion, wheeled robots are very common in robotics applications. Many highly complex robots are being developed in research laboratories, but wheeled robots remain the most used robot in real-world situations. One of the most significant downfalls of wheeled robots is their inability to navigate over large obstacles or steps without assistance. A wheeled robot is capable of climbing steps that are no larger than the radius of the robot's tires, but steps larger than this are impassable by simply rolling over the object. Active systems that have been designed for use on wheeled robots to lift the robot over a step are effective, but are generally not easily implemented on a range of robotic platforms. Also, the additional size, cost, and power required for the additional actuators is a major drawback to these options. A solution to these problems is a novel, passive dynamic system that is inertially excited by the motion of the robot to allow the robot to rotate on each axle and "hop" over the step. The system that was investigated for this project is a sliding mass-spring that shifts forward and backward based on the acceleration of the base robot. With high acceleration, the mass is pushed towards the rear wheel from an inertial force and compresses a spring that creates a moment on the body to induce rotation. This torque can cause the robot to "pop a wheelie", lifting its front wheels off the ground. To pull the rear wheels up, the inertial force from a large deceleration of the robot shifts the mass forward and extends a spring. These effects result in a moment acting in the opposite direction that can rotate the robot on its front axle and pull the rear wheels up. By coordinating the acceleration and deceleration of the robot, the front wheels can lift over a step and the rear wheels can be pulled up afterward — both actions being a product of inertial actuation. This passive system does not need additional actuators or direct control of the sliding mass, so it can be more durable over a robot's lifetime. Other advantages of this system are that the design is simple, cost-effective, and can be adjusted and retrofit to a different wheeled robot in the future with little effort. By deriving the equations of motion of this inertially actuated sliding mass, the dynamics show how design parameters of the system can be tuned to better optimize the overall step-climbing process. A computer simulation was created to visualize the robotic step-climbing process and demonstrate the effects of changing design parameters. An implementation of this sliding mass system was added to a wheeled robot, and the results from experiments were compared to simulated trials. This research has shown that an inertially actuated sliding mass can effectively enable a wheeled robot to climb a step that was previously impassable and that the system can be tuned for other wheeled robots using an understanding of the system dynamics. Master of Science

Previous work in the Railway Technology Laboratory at Virginia Tech focused on better capturing the dynamics of the friction wedge, modeled as a 3D rigid body. The current study extends that work to a half-truck model treated as an application of multibody dynamics with unilateral contact to model the friction wedge interactions with the bolster and the sideframe. The half-truck model created in MATLAB is a 3D, dynamic, multibody dynamics model comprised of four rigid bodies: a bolster, two friction wedges, and a sideframe assembly. The model allows each wedge four degrees of freedom: vertical displacement, longitudinal displacement (between the bolster and sideframe), pitch (rotation around the lateral axis), and yaw (rotation around the vertical axis). The bolster and the sideframe have only the vertical degree of freedom. The geometry of these bodies can be adjusted for various simulation scenarios. The bolster can be initialized with a pre-defined yaw (rotation around the vertical axis) and the sideframe may be initialized with a pre-defined pitch/toe (rotation around the lateral axis). The multibody dynamics half-truck model simulation results have been compared with results from NUCARS®, an industry standard train modeling software, for similar inputs. The multibody dynamics models have also been extended to a variably damped full-truck model and a variably damped half-truck warping model. These models were reformulated to react dynamically to simulated truck warp inputs. The ability to better characterize truck warping properties can prevent train roll over and derailments from truck hunting. In a quarter-truck variably damped configuration the effects of a curved wedge surface has also been explored. Actual friction wedges have surfaces which are slightly curved, this iteration in the multibody dynamics friction wedge modeling attempts to draw one step closer to actual friction wedge geometry. This model lays the ground work for a contact dependant wedge wearing model based on material properties and tribology. Master of Science

Autonomous ground vehicle operations, such as those found in the 2007 DARPA Urban Challenge, require a reliable and capable vehicle platform. To meet this requirement, an autonomous ground vehicle platform based on a 2005 Ford Escape Hybrid was developed for operations in urban environments. The vehicle conversion, dubbed Odin, contains a drive-by-wire system that is highly integrated with the OEM systems, providing throttle, steering, shifting, and braking actuation. The vehicle also includes a controller that provides low-level longitudinal using a map-linearized PI controller and lateral curvature control using a bicycle model. The control algorithms proved capable of controlling the vehicle at a level acceptable for autonomous operations. Communications are implemented using the Joint Architecture for Unmanned Systems (JAUS) using custom messages to enhance interoperability potential. The net result is a highly capable autonomous vehicle platform that was validated when Odin successfully completed the 60 mile Urban Challenge. Master of Science

There are many forms of speed control for an autonomous ground vehicle currently in development. Most use a simple PID controller to achieve a speed specified by a higher-level motion planning algorithm. Simple controllers may not provide a desired acceleration profile for a ground vehicle. Also, without extensive tuning the PID controller may cause excessive speed overshoot and oscillation. This paper examines an approach that was designed to allow a greater degree of control while reducing the computing load on the motion planning software. The SpAM+PI (Speed-based Acceleration Map + Proportional Integral controller) algorithm outlined in this paper uses three inputs: current velocity, desired velocity and desired maximum acceleration, to determine throttle and brake commands that will allow the vehicle to achieve its correct speed. Because this algorithm resides on an external controller it does not add to the computational load of the motion planning computer. Also, with only two inputs that are needed only when there is a change in desired speed or maximum desired acceleration, network traffic between the computers can be greatly reduced. The algorithm uses splines to smoothly plan a speed profile from the vehicle's current speed to its desired speed. It then uses a lookup table to determine the correct pedal position (throttle or brake) using the current vehicle speed and a desired instantaneous acceleration that was determined in the splining step of the algorithm. Once the pedal position is determined a PI controller is used to minimize error in the system. The SpAM+PI approach is a novel approach to the speed control of an autonomous vehicle. This academic experiment is tested using Odin, Team Victor Tango's entry into the 2007 DARPA Urban Challenge which won 3rd place and a $500,000 prize. The evaluation of the algorithm exposed both strengths and weaknesses that guide the next step in the development of a speed control algorithm. Master of Science

The tire is one of the most complex subsystems of the vehicle. It is, however, the least understood of all the components of a car. Without a good tire model, the vehicle simulation handling response will not be realistic, especially for maneuvers that require a combination of braking/traction and cornering. Most of the simplified theoretical developments in tire modeling, however, have been limited to on-road tire models. With the availability of powerful computers, it can be noted that majority of the work done in the development of off-road tire models have mostly been focused on creating better Finite Element, Discrete Element, or Boundary Element models. The research conducted in this study deals with the development of a simplified tire brush-based tire model for on-road simulation, together with a simplified off-road wheel/tire model that has the capability to revert back to on-road trend of behavior on firmer soils. The on-road tire model is developed based on observations and insight of empirical data collected by NHSTA throughout the years, while the off-road tire model is developed based on observations of experimental data and photographic evidence collected by various terramechanics researchers within the last few decades. The tire model was developed to be used in vehicle dynamics simulations for engineering mobility analysis. Vehicle-terrain interaction is a complex phenomena governed by soil mechanical behavior and tire deformation. The theoretical analysis involved in the development of the wheel/ tire model relies on application of existing soil mechanics theories based on strip loads to determine the tangential and radial stresses on the soil-wheel interface. Using theoretical analysis and empirical data, the tire deformation geometry is determined to establish the tractive forces in off-road operation. To illustrate the capabilities of the models developed, a rigid wheel and a flexible tire on deformable terrain is implemented and output of the model was computed for different types of soils; a very loose and deformable sandy terrain and a very firm and cohesive Yolo loam terrain. The behavior of the wheel/tire model on the two types of soil is discussed. The outcome of this work shows results that correlate well with the insight from experimental data collected by various terramechanics researchers throughout the years, which is an indication that the model presented can be used as a subsystem in the modeling of vehicle-terrain interaction to acquire more insight into the coupling between the tire and the terrain. Ph. D.

Localization is an essential part of any autonomous vehicle. In a simple setting, the localization problem is almost trivial, and can be solved sufficiently using simple dead reckoning or an off-the-shelf GPS with differential corrections. However, as the surroundings become more complex, so does the localization problem. The urban environment is a prime example of a situation in which a vehicle's surroundings complicate the problem of position estimation. The urban setting is marked by tall structures, overpasses, and tunnels. Each of these can corrupt GPS satellite signals, or completely obscure them, making it impossible to rely on GPS alone. Dead reckoning is still a useful tool in this environment, but as is always the case, measurement and modeling errors inherent in dead reckoning systems will cause the position solution to drift as the vehicle travels eventually leading to a solution that is completely diverged from the true position of the vehicle. The most widely implemented method of combining the absolute and relative position measurements provided by GPS and dead reckoning sensors is the Extended Kalman Filter (EKF). The implementation discussed in this paper uses two Kalman Filters to track two completely separate position solutions. It uses GPS/INS and odometry to track the Absolute Position of the vehicle in the Global frame, and simultaneously uses odometry alone to compute the vehicle's position in an arbitrary Local frame. The vehicle is then able to use the Absolute position estimate to navigate on the global scale, i.e. navigate toward globally referenced checkpoints, and use the Relative position estimate to make local navigation decisions, i.e. navigating around obstacles and following lanes. This localization solution was used on team VictorTango's 2007 DARPA Urban Challenge entry, Odin. Odin successfully completed the Urban Challenge and placed third overall. Master of Science