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Industries are revolutionizing everyday as we step into industrial 4.0 with enhanced and smart technologies ruling every micro hub. The Information Technology industry is running with thousands of employees at once needs more power management system. The proposed system identifies the entry of any person at the entrance. The identified person’s cabin or workspace power is turned on with simpler but efficient way of communication as LoRa module is used. The person is face recognized with the assistance of cameras at the entrance and their ID is transmitted to the Distribution box controller where the Air conditioner and other local supplies are automated to be turned on meanwhile. An employee’s ID and his position in the industry are matched in the industry with distribution box control which is reprogrammable. This LoRa WAN network is used effectively with gateways to transport less data to longer range as the system deals with large network. The end node of this network is fitted with energy meter and localized controller to calculate the power consumed as well control the appliances, which also gives a leverage of using implementing this at home.

A novel sliding mode control strategy is proposed to solve the trajectory tracking control problem of an offshore antenna platform, which uses a Stewart-type parallel mechanism and has a large orientation workspace. To obtain comprehensive posture parameters of the offshore antenna platform, a posture compensation algorithm using the information of azimuth and elevation is proposed. Considering known limb lengths, a state observer which based on a super-twisting algorithm is presented to obtain limb velocities. To solve the trajectory-tracking control problem of the platform, a modified nonsingular terminal integral sliding mode controller is proposed. To reduce chattering, the sliding mode controller is equipped with a higher order super-twisting algorithm. The Lyapunov theory was used to prove its stability. Simulation results on a large-orientation workspace offshore antenna platform demonstrate its superiority over three other controllers. Compared with the traditional sliding mode controller with super-twisting algorithm, the integral of the squared error of the proposed control strategy is 49.49% lower.

Automatic 3D navigation control of microrobot in large microenvironment is one of the primary challenges hindering its applications. In this article, we present a systematic approach to use an electromagnetic manipulation system to deal with this challenge. Two movable orthogonal microscopic cameras scan the microenvironment on the top view and side view to build a stereo occupancy map automatically. The initial position of microrobot can be located on the basis of the similarity curves generated by the scanning sequences. In accordance with the distribution characteristic of electromagnetic fields in workspace, an enhanced rapidly exploring random tree algorithm is proposed to avoid obstacles in the complex environment. To ensure continuous visual servo in wide range, a field-of-view tracking method is developed using a specific image definition evaluation algorithm. A prescribed performance controller with disturbance observer is designed, which guarantees that the microrobot can remain in the view of microscopic cameras, and the transient and steady-state performance of the system can satisfy the expected requirements. A set of experiments are performed to verify the effectiveness of the proposed automatic 3D navigation strategy. Experimental results show that the microrobot can navigate automatically in a $\bm {12\,\times 10\,\times \text{10-mm}}$ microenvironment containing obstacles, and achieve reliable field-of-view tracking and path following at high speed.

Hyper-redundant manipulators (HRMs) are widely used in minimally invasive surgery (MIS) because of their flexibility, dexterity, and compactness. However, when an external load acts on an HRM, its bending motion is disturbed and the workspace decreases. In addition, the external load increases the cable tension, and thin cables may break due to their low breaking strengths. This paper proposes a cable-movable rolling joint that increases the workspace for MIS under an external load and reduces the actuating cable tension through cable movement. Further, it presents an optimized motion estimation analysis method that verifies the manipulator performance by finding the equilibrium position and predicting the shape and tip position. The simulated manipulator exhibited a shape similar to that of the prototype and an average tip position difference of 4.59% based on the prototype length. Under an external load of 150 g, the workspace and cable tension of the prototype were 27.32% larger and 1.79 N lower than those of the conventional rolling joint, respectively. The new cable-movable mechanism and estimation analysis method will help improve the bending performance and position accuracy of HRMs for MIS.

Unintended motion has been one of the major causes of intra-operative injuries in tele-operated surgeries. Due to the large workspace discrepancy between master and slave manipulators, the tip of the slave may deviate from the intended master command without prior notice, when the slave is moved beyond its joint limits. Conventional solutions like the constrained optimization based Virtual Fixture (VF) method suffered from non-intuitive tip motion management and unnatural haptics in high-dimensional systems. To this end, we propose a Task Space Virtual Fixture (TSVF) architecture to systematically address those issues by forbidden-region VF design. It decomposes the high-dimensional task space into low-dimensional task sub-spaces according to its inherent topology. In each sub-space, we design a human-centric TSVF geometry and controller to manage the tip behavior by exploiting the nonlinear kinematics mapping. This architecture builds a real-time TSVF system with natural and predictable haptics. To showcase this concept, we designed and implemented the proposed TSVF system for the state-of-the-art surgical system, da Vinci Research Kit (dVRK). Simulations, experiments, and human-factor user study verified its effectiveness and intuitiveness. In the user study, our proposed TSVF system demonstrated the most easy-to-understand tip behavior and showed a significant positive effect over haptics likeability.

Robot simulation is an important way to verify the correctness of model and feasibility of design. Taking the Delta parallel mechanism as the effector of a weeding robot, this paper designs the workspace for the weeding mechanism in the field of corn seedlings, when each corn seedling has three to five leaves, and then carries out a simulation analysis on the workspace of the weeding mechanism. To realize variable rate precision spraying, the authors planned a three-segment gate-shaped trajectory for the end effector, detailed the trajectory under the joint coordinate system, and analyzed the motion law of S-curve motion profile. Then, the law of each kinematics parameter was solved on MATLAB, and plotted into graphs. Based on the simulation results, a prototype was developed for the proposed weeding mechanism, and subject to weeding experiments to obtain the end effector trajectory. Compared with the simulated results, the maximum deviation in the end effector trajectory during actual operation was 11.58%; the prototype could complete a weeding action every 2.8 s, while advancing at the speed of 0.4 m/s. The results fully demonstrate the feasibility of applying Delta parallel mechanism in weeding, and the reasonability of our workspace design and trajectory planning.

This paper presents a new bridge-type compliant displacement amplifier embedded with Scott-Russell mechanism. Based on this design, a novel compliant XY micro-positioning stage is also designed, analyzed and tested to illustrate the advantages of the proposed amplifier. The main feature of the new amplifier is to employ Scott-Russell mechanism to replace one arm of the compound bridge-type mechanism, aiming to improve its lateral stiffness and the natural frequency in the working direction. The compliant XY micro-positioning stage is driven by two novel bridge-type amplifiers with orthogonal distribution. Double parallelogram guide mechanisms are added at the output ends of the bridge-type mechanisms to further lower the parasitic movements of the XY stage. Then, an analytical model based on the stiffness matrix transfer method is established for the static and dynamic characteristics of stage, which are also verified by performing finite element analysis. Finally, an experimental prototype is manufactured and its static and dynamic performances are tested. The test results demonstrate that the stage can realize a workspace of 181.0 μm × 179.5 μm with motion resolution of 20 nm and a maximum coupling error of 1.07%. The natural frequencies of XY stage along the working direction are 178 Hz and 248 Hz respectively when the PZTs are not installed or installed. Additionally, the trajectory tracking performance of the stage is also preliminarily evaluated. All of the results obtained from the analytical model, finite element analysis and experimental tests verify the effectiveness of the novel bridge-type displacement amplifier and the compliant XY micro-positioning stage.

A magnetic manipulation system for medical applications is designed with its coils widely distributed over a sufficiently large space such that a patient can lie down, an operator can enjoy accessibility and the workspace is sufficiently large. However, this design makes the current references asymmetrical. Moreover, at the corners, some references might exceed the coil current rating, and the magnetic field cannot be synthesized as desired. To address this overcurrent reference problem, this paper proposes a magnetic manipulation system controlled with the minimum infinity-norm current reference. In many magnetic manipulation systems, the current reference for a given motion command of the magnetic field is infinite. And the minimum infinity-norm current reference is the most feasible. The proposed control strategy presents an increased maximum synthesizable magnetic field in an arbitrary direction, including the worst-case direction, compared with the conventional field of Moore–Penrose inverse control. To verify the effectiveness, the worst-case direction of the magnetic field of each method is analytically derived. And, the controllable areas of the 8-coil magnetic manipulation system are compared. This paper also proposes a soft mode transition between the two methods for efficiency enhancement. The experimental results show the effectiveness of the proposed control strategy.

Soft robots made of elastic and compliant materials offer various advantages, such as safe interaction, adaptiveness, and easy fabrication. However, the highly dissipative nature of elastic materials intrinsically limits certain functions, such as force transmission, positioning accuracy, and load capability. Herein, we present a design approach for developing articulated soft robots with variable stiffness. We propose a bioinspired bistable articulated joint that consists of a rigid joint and bistable structures. We realize stiffness change through forming a locking function by triggering the bistable structure to switch between two stable states. The trigger force is generated by heating shape memory alloy springs connected to the bistable structures. After the locking function is triggered, the bending stiffness of the articulated joint is highly amplified. Moreover, the joint can be locked at different angles through mechanically preprograming bistable structures fabricated with a single 3D print. With this approach, we developed an articulated soft robot as a case study. The robot demonstrated variable stiffness, changeable configurations, and large workspace. Moreover, the approach proposed in this work provides valuable insights into the utilization of bistability for developing variable-stiffness robotic systems.

The compliant structure and influence of external forces usually result in complex deformation of soft continuum robots, which makes the accurate modeling and control of the robot challenging. In this work, we present a new variable curvature kinematic modeling approach for soft continuum robots by taking the external forces into consideration, achieving both accurate motion simulation and feedforward control of the robot. To this end, the variable curvature configuration is firstly parameterized based on the absolute nodal coordinate formulation (ANCF). Then, a kinematic model is developed to describe the mappings between the defined configuration space and the actuation space with payloads. With this model, we achieve accurate and fast motion simulation for the soft continuum robot with different payloads and input pressures within 1 millisecond, which is verified by a set of experiments. Finally, an inverse-model-based feedforward controller is developed for a two-section soft continuum robot. The experimental results of tracking complex trajectories verify the effectiveness of our model and control strategies. The average position error of the end-effector is 2.89% of the robot length. This work can also be served as a tool to design and analyze soft continuum robots with desired workspace.

The mapping relationship between the driving space and the workspace is essential for the precise control of a cable-driven hyper-redundant robot. For a hyper-redundant robot driven by cables, the relationships between the driving space and the joint space and between the joint space and the workspace were studied. A joint-decoupling kinematics analysis method was proposed and a kinematic analysis was presented. Based on the analysis of the coupling effect between the cable-driving space and the joint space, a decoupling analysis of the whole cable-driving space and joint space was conducted to eliminate the coupling effect between the joints, and the mapping relationship between the driving cables and the joint angles was obtained. Given the initial and target orientations of the hyper-redundant robot, the variation law for each joint angle was obtained using quintic polynomial trajectory planning and the pseudo-inverse Jacobian matrix, and then the driving cable variation law could be solved. Based on the results, the joint angle changes and the workspace trajectories were solved in turn. By comparing with the initial trajectory, the simulation results verified the appropriateness of the decoupling analysis.

This paper proposes a methodology for calibration of industrial robots that uses a concept of measurement sub-regions, allowing low-cost solutions and easy implementation to meet the robot accuracy requirements in industrial applications. The solutions to increasing the accuracy of robots today have high-cost implementation, making calibration throughout the workplace in industry a difficult and unlikely task. Thus, reducing the time spent and the measured workspace volume of the robot end-effector are the main benefits of the implementation of the sub-region concept, ensuring sufficient flexibility in the measurement step of robot calibration procedures. The main contribution of this article is the proposal and discussion of a methodology to calibrate robots using several small measurement sub-regions and gathering the measurement data in a way equivalent to the measurements made in large volume regions, making feasible the use of high-precision measurement systems but limited to small volumes, such as vision-based measurement systems. The robot calibration procedures were simulated according to the literature, such that results from simulation are free from errors due to experimental setups as to isolate the benefits of the measurement proposal methodology. In addition, a method to validate the analytical off-line kinematic model of industrial robots is proposed using the nominal model of the robot supplier incorporated into its controller.

Robot-assisted technology has been increasingly employed in the therapy of post stroke patients to deliver high-quality treatment and alleviate therapists’ burden. This paper introduces a novel parallel end traction apparatus (PETA) to supplement equipment selection. Considering the appearance and performance of the PETA, two types of special five-bar linkage mechanisms are selected as the potential configurations of the actuation execution unit because of their compact arrangement and parallel structure. Kinematic analysis of each mechanism, i.e., position solutions and Jacobian matrix, is carried out. Subsequently, a comparative study between the two mechanisms is conducted. In the established source of nondimensional parameter synthesis, the singularity, maximum continuous workspace, and performance variation trends are analyzed. Based on the evaluation results, the final scheme with determined configuration and corresponding near-optimized non-dimensional parameters is obtained. Then, a prototype is constructed. By adding a lockable translational degree of freedom in the vertical direction, the PETA can provide 2D planar exercise and 3D spatial exercise. Finally, a control system is developed for passive exercise mode based on the derived inverse position solution, and preliminary experiments are performed to verify the applicability of the PETA.

This study proposes a method for simultaneous implementation of performance improvement, decoupling of null space and workspace, and suppressing operational force for a hybrid control system with a redundant degree of freedom (RDOF). Hybrid control systems with RDOF are necessary for motion control systems to achieve future applications for human support systems and robots in unknown and open environments. This article shows that the acceleration controller performs decoupling of task (modal) spaces in the redundant system. Additionally, this article proposes a novel method based on the extension of an acceleration-based disturbance observer in modal space for position/force hybrid controllers to the redundant systems. The proposed method contributes to the suppression of operating (inertia) force and interference from the null space with the simplification of inverse kinematics. Experiments of the scaled bilateral control, which is one of the hybrid control systems for the master and slave systems with RDOF, are conducted to validate the proposed method.

This article presents the optimal current allocation and the magnetic force production associated with the hexapole electromagnetic actuation, wherein six electromagnets are used to control the magnetic field and exert the 3-D magnetic force on a specified microscopic magnetic particle in the 3-D workspace of the actuating system. It addresses four major issues in the inverse modeling of the multipole electromagnetic actuation, i.e., 1) redundancy; 2) coupling; 3) nonlinearity; and 4) position-dependency, and leads to the accurate and effective 3-D magnetic force production within the specified workspace. Specifically, the optimal inverse modeling of the hexapole electromagnetic actuation is derived to minimize the 2-norm of the $6 \times 1$ input current vector when applied to produce the desired 3-D magnetic force to propel the magnetic particle in aqueous solutions. The inverse model is implemented in a high-speed field programmable gate array system to realize the real-time current allocation, which is used to render the feedback stabilization of the magnetic trap. The accurate and effective 3-D force production through the optimal current allocation is experimentally validated.

Concentric tube robots are catheter-sized continuum robots that show dexterous movement for minimally invasive surgical procedures. However, one of the major challenges to the practical usage of concentric tube robots is their instability, which potentially leads to the risk of tissue rupture. The snapping problem is caused by tubes having a high bending to torsional stiffness ratio (BTSR). Past efforts have shown that anisotropic patterning on tubes can alleviate the snapping problem. This research investigates the design optimization of patterns to minimize BTSR while satisfying stiffness constraints. Using topology optimization methods, rhombus-shaped patterns were identified as the ideal shape for stability. The generated designs were validated through finite element analysis and experimental testing to show the change of BTSR and the elimination of the snapping problem. Extensive parametric study is performed to analysis the sensitivity of the design parameters and provide the design guidelines. While satisfying the constraints, the proposed design method demonstrated 0.28 of BTSR with a rhombus angle of 60 degrees and a volume fraction of 0.55. The optimized design potentially improves the workspace and versatile trajectories of concentric tube manipulators.

Compared with multi-axis CNC machines, industrial robots provide a new solution to complex surface machining due to the significant advantages of cost-effectiveness, good flexibility, and large workspace. However, the programming for robotic machining trajectory is complex and time-consuming, due to the limitations for robots to execute G-Code command generated via the CAD/CAM post-processing techniques. To this end, the paper proposed an effective methodology to generate the robotic machining trajectory by the conversion from G-Code commands for practical operations, in which the robotic machining system and the associated kinematic analysis are implemented using ABB IRB 2600 robot, as well as the interpretation of G-Code and robot control commands. The conversion relationship from G-Code to robot control commands is achieved with the information of the CL point parameters and machining configuration parameters. One off-line programming software, RobMach, is developed to simulate and validate the effectiveness of the robotic machining trajectory by loading G-Code file of one blade milling, and the generated robot control program can be directly sent to the robot’s controller for achieving the robotic machining capabilities, which can be extended to the machining operations of different industrial robots.

A multi-robot collaborative towing system fixed on floating base for high load marine work was established in this paper, and its dynamics and workspace were analyzed. An improved Monte-Carlo method was optimized, considering that this method cannot be directly used for the multi-robot system. Firstly, according to the structure of the system, the dynamics equations of the towing mechanism and the floating base were established by using the Newton-Euler method and rigid body dynamics, respectively. Then, an improved Monte-Carlo method was optimized, and the specific steps of solving the dynamic workspace by the optimized method were provided. Lastly, the system was divided into three types according to the actuator, and their dynamic workspace were simulated with a practical example by the traditional Monte-Carlo method and the optimized method. The simulation results show that, compared with traditional method, the optimized method has higher efficiency and can figure a workspace with clear boundary. Results of this study lay a basis for the subsequent trajectory plan and stability analysis of the system.

The asymmetry in bilateral teleoperation, i.e., the differences of mechanical structures, sizes, and number of joints between the master and slave robots, can introduce kinematicsr edundancy and workspace inequality problems. In this article, a novel shared autonomy control strategy is proposed for handling the asymmetry of bilateral teleoperation, which has two main contributions. First, to deal with kinematics redundancy, the proposed strategy provides a self-regulation algorithm of orientation that allows the operator to solely use the master position command to simultaneously control the slave’s position and orientation. Second, to deal with workspace inequality, the proposed strategy enables the slave’s workspace to be dynamically tunable to adapt to various task spaces without influencing the smoothness of the robot’s movement. The experiments on a platform consisting of a six-degree of freedom (DoF) UR10 robot and a 3-DoF haptic device are given to validate the effectiveness of the proposed control strategy., Funding agency:AI.MEE Program: AutoDIVE

This paper presents a unique optimal torso design selection technique for the dual seven-degree-of-freedom robot arm. This optimal design enhances the robot end-effector’s workspace with less operational stress. The selection procedure incorporates the von Mises stress and robot workspace analysis in different robot-torso mounting configurations. The torso design selection strategy includes the von Mises stress calculation numerically and by using SolidWorks static analysis for robot arm considered as bolted-fixed end cantilever beam. Followed by robot end-effector workspace analysis using inverse kinematics, which determines the maximum area covered by manipulated robot end-effector in 2-dimensional (2D) and 3-dimensional (3D) space. Subsequently, introducing a selection function for torso design. This selection function is calculated based on weighting coefficients (priority given to stress and workspace), von Mises stress, and workspace area. The selection technique concludes that the torso design with upper-arm mounting configuration is optimal for current robot application, i.e., assembly.

A novel backdrivable 3-[ R ( R R- R RR)SR] kinematically redundant (6+3)-degree-of-freedom (DOF) spatial hybrid parallel robot with revolute actuators is proposed for low-impedance physical human–robot interaction. The kinematic model is developed based on the constraint conditions of the robot. It is shown that the type II (parallel) singularities can be completely avoided, thereby yielding a very large translational and orientational workspace. A workspace analysis is presented in order to demonstrate the capabilities of the robot. Mechanisms are then introduced to use the redundant DOF of the robot to operate a gripper with the robot actuators, which are mounted on or close to the base, thus reducing the inertia of the moving parts. The architecture of the robot makes it possible to use direct drive motors, thereby making the robot easily backdrivable and allowing the use of a very simple and effective controller. A prototype of the robot is then designed and built and the large workspace of the robot as well as the effortless physical human–robot interaction are demonstrated. The controller of the robot is then described, including a position control mode and a control mode for physical interaction, which does not require the use of a force/torque sensor or joint torque sensors. Because of its backdrivability and low moving inertia, the robot is particularly well-suited for physical human–robot interaction, as demonstrated in the accompanying videos.

Remote center of motion (RCM) constraint has attracted many research interests as one of the key challenges for robot-assisted minimally invasive surgery (RAMIS). Although it has been addressed by many studies, few of them treated the motion constraint with an independent workspace solution, which means they rely on the kinematics of the robot manipulator. This makes it difficult to replicate the solutions on other manipulators, which limits their population. In this paper, we propose a novel control framework by incorporating model predictive control (MPC) with the fuzzy approximation to improve the accuracy under the motion constraint. The fuzzy approximation is introduced to manage the kinematic uncertainties existing in the MPC control. Finally, simulations were performed and analyzed to validate the proposed algorithm. By comparison, the results prove that the proposed algorithm achieved success and satisfying performance in the presence of external disturbances.

Continuum robots have high degrees of freedom and the ability to safely move in constrained environments. One class of soft continuum robot is the “vine” robot. This type of robot extends from its tip by everting or unfurling new material, driven by internal body pressure. Most vine robot examples store new body material in a reel at their base, passing it through the core of the robot to the tip, and like many continuum robots, steer by selectively lengthening or shortening one side of the body. While this approach to steering and material storage lends itself to a fully soft device, it has three key limitations: (i) internal friction of material passing through the core of the robot limits its length in tortuous paths, (ii) body buckling as the robot's body material is re-spooled at the base can prevent retraction, and (iii) constant curvature steering limits the robot's poses and object approach angles in a given workspace. This letter presents a hybrid soft-rigid robotic system comprising a soft vine robot body and a rigid, mobile, internal steering-reeling mechanism (SRM); this SRM is equipped with a reel for material storage, a bending actuator for steering, and is capable of actuating the robot at any point along its length. This hybrid configuration increases reach along tortuous paths, allows retraction, and increases the workspace. We describe the motivation for the device, generate its mathematical models, present its methods of operation, and verify experimentally the models we developed and the performance improvements over previous vine robots.

This letter proposes a nonlinear model predictive control (NMPC) approach for real-time planning of point-to-point motions of serial robot manipulators that share their workspace with a human. The NMPC law solves a nonlinear program online, based on a kinematic model, and guarantees safety by constraining the robot speed within the time-varying bounds determined by the speed-and-separation-monitoring (SSM) principle. Closed-loop stability is proven in detail, and the performance (in terms of productivity) of the proposed method is tested against standard SSM schemes via experiments on a Kinova Gen3 robot.

The exploration and inspection of narrow spaces in industrial plants require the use of long-reach redundant manipulators with large three-dimensional (3D) workspaces. To this end, in a previous work, a coupled tendon-driven articulated manipulator with a total length of 10 m and yaw joints for 3D motion was developed. This study focuses on employing the antagonistic tension in a yaw joint to support a tendon that drives a pitch joint with high gravitational loading. Herein, a tension control method that employs the antagonistic tension to reduces the amount of tension required to support the weight of an arm is proposed. The effectiveness of the proposed method is evaluated based on the workspace volume of the previously developed Super Dragon, and the results demonstrate that the proposed method expands the workspace by up to 45%.

Tower cranes are a class of important and useful tools for the transportation of large cargoes, especially in high building construction. Moreover, the combination of jibs’ rotational movements and trolleys’ translational movements can fulfill three-dimensional payload transportation in a huge outdoor workspace. However, complicated dynamics and different unfavorable environmental conditions in practice make the effective control of tower cranes very challenging. In this article, based on the original dynamic models without any linearization manipulations, we present a new output feedback control method to accomplish rapid jib and trolley positioning and payload sway suppression. In particular, the velocity signals are accurately obtained by an elaborately designed observer, instead of numerical differentiation manipulations to the measurable output variables (which may distort the original velocities to some extent). Based on the velocity estimates, the suggested controller can also handle uncertain friction. Additionally, the actuator constraints are fully considered during controller design, i.e., the calculated control inputs are both within the permitted ranges, thereby avoiding actuator saturation and degrading the control performance. For the entire closed-loop system, including the proposed controller, the state observer, and tower cranes, the asymptotic stability is strictly proven by Lyapunov-based techniques. Finally, some comparative and robustness verifications are implemented by hardware experiments.

In the present study, the over-constrained hybrid manipulator R(2RPR)R/SP+RR is considered as the research objective. In this paper, kinematics of the hybrid manipulator, including the forward and inverse position, are analyzed. Then, the workspace is checked based on the inverse position solution to evaluate whether the workspace of the hybrid manipulator meets the requirements, and the actual workspace of the hybrid robot is analyzed. After that, the force analysis of the over-constrained parallel mechanism is carried out, and an ADAMS-ANSYS rigid-flexible hybrid body model is established to verify the simulation. Based on the obtained results from the force analysis, the manipulator structure is designed. Then, the structure optimization is carried out to improve the robot stiffness. Finally, calibration and workspace verification experiments are performed on the prototype, cutting experiment of an S-shaped aluminum alloy workpiece is completed, and the experiment verifies the machining ability of the prototype. This work conducts kinematics, workspace, force analyses, structural optimization design and experiments on the over-constrained hybrid manipulator R(2RPR)R/SP+RR, providing design basis and technical support for the development of the novel hybrid manipulator in practical engineering.

This study presents a novel four-degrees-of-freedom parallel gripper with potential application to industrial automation. The gripper adopts a parallel grasping mode on objects and can independently complete in-plane horizontal and vertical motions and in-hand twisting motion. Kinematic and dynamic models of the gripper–object system are developed. The controllable internal force acting on the object is calculated to obtain the minimum driving force/torque. An energy-based manipulability index is developed on the basis of the derived solutions. The numerical simulation includes a comparison between the MATLAB model and the ADAMS model to verify the motion forms of the parallel gripper and the rationality of analytical modeling studies. Manipulability performance is evaluated along the transportation path of the object. Results indicate that the gripper can achieve horizontal transmission to supplement the workspace of a robotic arm, and it exhibits relatively better performance in in-hand manipulation and in-plane vertical transmission.

In this work, the structural design of a structure-simplified parallel Delta robot is presented, by considering the kinetostatics, kinematic dexterity and workspace. An approach to normalize the di...

In aircraft assembly, robot drilling system has been widely used to enhance the efficiency and quality of assembly holes' manufacturing. However, the industrial robot used by the drilling robot has low absolute positioning accuracy, which cannot meet the hole positioning accuracy requirement of aircraft components, so the drilling robot must be calibrated. The kinematic calibration effect is sensitive to the selection of measurement configurations. Although different observability indexes have been proposed to evaluate the measurement configurations, it is difficult to obtain precise kinematic parameters and minimize the uncertainty of end-effector positions simultaneously with a single observability index. At the same time, current measurement configurations optimization algorithms are still prone to fall into local optimization trap and boundary optimization trap. In order to improve the calibration accuracy of the drilling robot, an improved multi-objective particle swarm optimization algorithm was proposed to search the measurement configurations in the limited workspace, and the “rebound” particle was proposed to avoid local convergence. The effectiveness of the proposed algorithm was verified by simulations and calibration experiments of a drilling robot with KUKA KR500L340-2. Results show that the proposed algorithm can effectively obtain the measurement configurations with the maximum comprehensive observability index, and the positions of the measurement configurations could avoid the search boundary. Meanwhile, more accurate kinematic parameters of the drilling robot can be calculated by using the optimal measurement configurations searched by the proposed algorithm, and the end-effector position accuracy is 26.94% higher than that calibrated with randomly selected measurement configurations.

In this work, the design, modeling, dimensional synthesis, and experimental characterization of a dexterous robotic hand based on the Stewart-Gough parallel manipulator are presented. The mechanism consists of three parallel linkage fingers with six prismatic actuators that control manipulation. An additional actuator maintains stable grasping forces. A computational model to predict the hand's workspace is then utilized to determine the optimal design parameters that maximize the workspace size and manipulability. A physical prototype based on the optimized parameters is built and experimentally characterized to assess its performance (Figure 1).

In this article, we propose a robust hierarchical inverse dynamics control scheme for redundant manipulators, which guarantees both predefined-time convergence of regulation tasks and robustness against model uncertainties/disturbances. Predefined-time convergence of a robotic task means that the task error is regulated to the origin at a desired preset time, independently of the initial state of the robot. The strict hierarchy of tasks is ensured by the so-called dynamic consistency, which avoids conflicts between decoupled task constraints. Thus, it enables the robot with more dexterity for reaching targets in its workspace while overcoming obstacles and joint limits. Predefined-time convergence facilitates the design of a time schedule to execute sequential and simultaneous tasks. All these features are supported by a stability analysis and experiments with two torque-controlled mobile manipulators in pick-and-place applications.

Hopping height control is one of the difficult problems in legged control. Many kinds of research employ a leg spring for the supplement of energy, and model the robot as a spring-mass model. Feedback linearization enables to cancel the nonlinear terms theoretically. However, it is difficult to identify the nonlinear terms including the parameters precisely in the real world. This paper nominalizes the robot dynamics as the desired spring-mass system applying a disturbance observer. In order to realize the desired characteristics of the spring and the mass, the disturbance including the nonlinear terms is rejected firstly by a disturbance observer. To make the mass in the workspace as constant, the nominal inertia of the disturbance observer in the joint space is varied. Next, by adding the desired virtual elastic force, the robot dynamics is nominalized as the desired spring-mass system. Based on the nominalized spring-mass dynamics, hopping-height control using energy/phase control is implemented. While energy control is often used for hopping height control, the energy/phase control enables the hopping-height control and the spring-mass oscillation simultaneously. Constant hopping-height and stepwise hopping height are realized experimentally through the proposed control method. The simulations in the case of the ideal dynamics are also conducted for comparison.

This paper presents a novel four degrees of freedom (DOF) parallel mechanism with the closed-loop limbs, which includes two translational (2T) DOF and two rotational (2R) DOF. By connecting the proposed parallel mechanism with the guide rail in series, the 5-DOF hybrid robot system is obtained, which can be applied for the composite material tape laying in aerospace industry. The analysis in this paper mainly focuses on the parallel module of the hybrid robot system. First, the freedom of the proposed parallel mechanism is calculated based on the screw theory. Then, according to the closed-loop vector equation, the inverse kinematics and Jacobian matrix of the parallel mechanism are carried out. Next, the workspace stiffness and dexterity analysis of the parallel mechanism are investigated based on the constraint equations, static stiffness matrix and Jacobian condition number. Finally, the correctness of the inverse kinematics and the high stiffness of the parallel mechanism are verified by the kinematics and stiffness simulation analysis, which lays a foundation for the automatic composite material tape laying.

In this paper, the open-chain arm containing flexible links connected through telescopic joints is investigated so as to replace robotic chains with revolute joints. In this manipulator, telescopic joints are considered by a simultaneous motion combination of the prismatic and revolute joints. In comparison with revolute–prismatic joints in which prismatic joint hubs are utilized, telescopic joints lack the hub, and the linear motion is generated via a gear. Accordingly, the flexible link is not placed inside the hub. In fact, the link is merely divided into two sections each at a time step. The front section which is considered in the motion equations is placed at the back of the hinge’s point. This part solely creates vibration, which probably affects the motion of other sections. This type of manipulator’s joints due to the structure benefits consists of the optimum weight, simple mechanism, extended workspace acceptable for robotic tools, industrial machinery, and domestic systems. To derive motion equations of N-link flexible manipulator with telescopic joints system, the Euler–Lagrange formulation is employed. The obtained equations are in the time-varying form, and the manipulator link length changes during motion. The derived equations are simulated for a two-link system with different elasticity values, and the results are then analyzed to verify the outcomes. The bifurcation analysis has also been used to prevent unstable vibrations and chaotic responses. It should be noticed that this type of manipulator can be used in a fast and precise mechatronics' system for utilization in space exploration, space station, and spacecraft as well.

This study is aimed at finding the entire points that a manipulator can launch an object onto by an optimal motion. These points are called throw-able workspace, which are located outside the reachable workspace of the robot. From an optimization point of view, some throwing parameters can be found to decrease motion cost. In this paper, by using this concept, the best combination of throwing and trajectory planning is attempted. The proposed method consists of two basic ideas: first, defining the optimal throwing problem as the optimal control problem (OCP) and solving it using the indirect solution approach based on the fundamental lemma of calculus of variations. To achieve the best release angle and speed, the throwing equation of motion is applied as a moving-end boundary condition (BC). Second, based on the obtained optimal throwing, an algorithm is presented to calculate the maximum throw-able workspace. The simulation results demonstrate the effectiveness of the proposed framework for both single link and spatial two-degree-of-freedom throwing robots.

Control parameter designing is an essential issue for industrial robot applications, in which the dynamic characteristics of robots play an important role. This article investigates the dynamic and control parameter design of a hybrid spray-painting robot with parallelogram structures to improve its tracking performance. The dynamic model of the robot is derived, and its intrinsic dynamic properties, such as time-varying characteristics, decoupling driving properties, and the contribution of each component to the total driving torque, are investigated. Based on the robot dynamic analysis, the comprehensive performance of the robotic mechatronic system is examined, and several principles for control parameter design are presented. Finally, on the basis of the small noise excitation method, a strategy to determine the robot pose for control parameter tuning is proposed. The strategy is experimentally verified to improve the consistency of motion accuracy in the entire workspace effectively.

This article addresses the problem of cooperative object transportation for multiple underwater vehicle manipulator systems (UVMSs) in a constrained workspace with static obstacles, where the coordination relies solely on implicit communication arising from the physical interaction of the robots with the commonly grasped object. In this article, we propose a novel distributed leader–follower architecture, where the leading UVMS, which has knowledge of the object's desired trajectory, tries to achieve the desired tracking behavior via an impedance control law, navigating in this way, the overall formation toward the goal configuration while avoiding collisions with the obstacles. On the other hand, the following UVMSs estimate locally the object's desired trajectory via a novel prescribed performance estimation law and implement a similar impedance control law that achieves tracking of the desired trajectory despite the uncertainty and external disturbance in the object and the UVMS dynamics, respectively. The feedback relies on each UVMS's force/torque measurements and no explicit data is exchanged online among the robots, thus reducing the required communication bandwidth and increasing robustness. Moreover, the control scheme adopts load sharing among the UVMSs according to their specific payload capabilities. Finally, various simulation studies clarify the proposed method and verify its efficiency.

Cable-driven parallel robots (CDPRs) are a new type of parallel robots that use cables to control a mobile platform. They possess several advantages, including large workspace, low inertia, and high payload capacity. However, there are several problems in the high-precision trajectory tracking control of CDPRs. On the one hand, all the cables must remain in tension during the entire motion process. On the other hand, the controller design is subjected to model uncertainties and external disturbances. Accordingly, this article proposes a robust synchronization control (RSC) scheme in the cable length space to achieve high-precision trajectory tracking. The synchronization control ensures motion coordination among all the cables and prevents cable relaxation, whereas the robust control eliminates modeling errors and restrains external disturbances. The uniformly ultimate boundedness of the tracking and synchronization errors in the closed-loop system equation was proved using the Lyapunov theory. Simulations and experiments of the trajectory tracking control were both implemented on a three-degree-of-freedom CDPR. Compared with the adaptive robust control scheme and the augmented proportional derivative scheme on the premise of the approximate energy consumption, the proposed RSC scheme could reduce not only the tracking errors of the cables but also the synchronization errors between adjacent cables. Moreover, the RSC scheme could significantly improve the trajectory tracking accuracy of the mobile platform. The robustness of this scheme was verified using load experiments and torque-disturbance experiments.

Overhead manipulation tasks often require collaborations between two operators, which becomes challenging in confined spaces such as in a compartment. Supernumerary Robotic Limb (SuperLimb), as a promising wearable robotic solution, can provide assistance in terms of broader workspace, wider manipulation functionalities and safer working conditions. However, the safety concerns of human-centered SuperLimb interaction mechanisms are rarely studied to date, particularly regarding human standing balance. This study proposes a balance controller by which one individual operator can accomplish overhead tasks with the assistance of SuperLimb via tunable interaction force and supporting force regulation. The SuperLimb-human interaction is modeled and a dynamics control method based on QR decomposition (also known as QR factorization, in which a matrix is factorized into an orthogonal matrix and an upper triangular matrix) is adopted to decouple joint torques of the SuperLimb and the interaction forces. Therefore, the supporting forces can be regulated independently to guarantee the operator-SuperLimb interaction forces in a safe region. Force plate is used for measuring the CoP position as an evaluation method of the standing balance. The critical horizontal push force is learned through experiment to guide the balance controller. This method is implemented on a SuperLimb prototype worn on the operator's back, to provide necessary supporting forces on overhead object while allowing the operator to move freely underneath.

Robots with kinematic loops are known to have superior mechanical performance. However, due to these loops, their modeling and control is challenging, and prevents a more widespread use. In this letter, we describe a versatile Inverse Kinematics (IK) formulation for the retargeting of expressive motions onto mechanical systems with loops. We support the precise control of the position and orientation of several end-effectors, and the Center of Mass (CoM) of slowly walking robots. Our formulation safeguards against a disassembly when IK targets are moved outside the workspace of the robot, and we introduce a regularizer that smoothly circumvents kinematic singularities where velocities go to infinity. With several validation examples and three physical robots, we demonstrate the versatility and efficacy of our IK on overactuated systems with loops, and for the retargeting of an expressive motion onto a bipedal robot.

This study presents the design, analysis, dynamical modeling and control of a planar, flexure based closed chain compliant mechanism. Mechanism is designed as a single piece and comprised of rigid-flexure links connected in series. Base links of the mechanism can be actuated through two servo motors and translated along the horizontal direction using two step motors. Two servo motors are mounted on a rail-cart system and carts are equipped with belt drive to enable horizontal displacement. Dynamical model of the mechanism is derived by adapting pseudo rigid body modeling method, vector closure loop equations, Euler’s laws of motion and geometric constraints. Mechanism is 3D printed using thermoplastic polyurethane filament (TPU), motion of the mechanism is video recorded and position of the tip along with the motion of center of each links are captured using image processing. Mathematical model is simulated in Matlab Simulink and validated with the experimental data. A reference trajectory drawn within the workspace of the mechanism on iPad is successfully traced in real time using the simplified model, mirror imaging program and inverse kinematics. The proposed mechanism can be utilized as a haptic device and a compliant manipulator in industrial applications where high precision and larger workspace is desired.

Serial robots provide an ideal alternative for friction stir welding of large-scale spatial curve welding seam due to their high flexibility and large workspace. However, the low stiffness of a serial robot will definitely affect its welding accuracy. In order to enhance the stiffness of the serial robot in completing friction stir welding tasks, this paper proposes a method of constructing the hybrid stiffness index. This method uses the sigmoid function to process the dexterity or joint limit index and applies it to the stiffness index as a weight coefficient. Then the soft stiffness index with dexterity constraint or joint limit constraint is constructed respectively, and these two hybrid stiffness indices have the same dimension as the stiffness index. Subsequently, the dimension synthesis of the ZK-500 serial robot is completed by maximizing the global soft stiffness index with dexterity constraint. Finally, based on the soft stiffness index with joint limit constraint, a joint trajectory planning algorithm for the ZK-500 robot and positioner system is proposed. The result of simulations shows that the soft stiffness index with a joint limit constraint can not only ensure the stiffness performance but also improve the smoothness of the joint trajectory in the robot trajectory planning task.

This paper has proposed a program analysis method over the current state of the workspace of an anthropomorphic manipulator using the Mathcad software application package (USA). The analysis of the manipulator workspace helped solve the following sub-tasks: to calculate the limits of the grip reach, to determine the presence of "dead zones" within the manipulator workspace, to build the boundaries of the manipulator workspace. A kinematic scheme of the manipulator typically provides for at least five degrees of mobility, which is why in the three-dimensional Cartesian coordinate system the work zone boundaries represent the surfaces of a complex geometric shape. The author-devised method makes it possible to construct the projections of the boundaries of the manipulator's work zone onto the coordinate planes in the frame of reference associated with the base of the robot. Using Mathcad's built-in features makes it possible to effectively solve the above sub-tasks without wasting time developing specialized software. The Mathcad software application package provides for the possibility of a symbolic solution to the first problem of the kinematics of an industrial robot, that is, the program generates analytical dependences of the coordinates for special point P (pole) of the grip on the trigonometrical functions of the generalized coordinates. The resulting analytical dependences are used for kinematic and dynamic analysis of the manipulator. Special features in constructing mathematical models when using the Mathcad software application package have been revealed. Simulating the manipulator movement taking into consideration constraints for kinematic pairs, the drives' power, as well as friction factors, makes it possible to optimize the parameters of the manipulator kinematic scheme. An example of the analysis of the working space of an anthropomorphic manipulator with five degrees of mobility has been considered. The reported results could be used during the design, implementation, modernization, and operation of manipulators.

SUMMARYIn this paper, a new type of biped mobile robot is designed. Each leg of the robot is a 6 degree-of-freedom (DOF) parallel mechanism, and each leg has three relatively fixed landing points. The leg’s structure gives the robot better performance on large carrying capacity, strong environmental adaptability and fast moving speed simultaneously. At the same time, it helps the robot move more steadily and change direction more simply. Based on the structural features of the leg, the inverse kinematics model of the biped robot is established and a unified formula is obtained. According to an analysis of robot’s workspace, gait planning is completed and simulated. Finally, the special case that the robot can keep the upper body horizontal while walking on a slopy surface is validated.

Teleoperated robots are commonly used in minimally invasive surgery as they can control surgical instruments at a distance. An operator sends the motion command via a master console, which must convert these into suitable slave instrument actuator inputs for intuitive interaction. However, most master-slave systems available to date use incremental task-space control and clutching, which introduces a discontinuity and orientation misalignment between the master control handle and slave instrument, with a consequent impact on task performance. In this article, we proposed a new master manipulator design to compensate for misalignment mechanically. The modular gimbal consists of a passive decoupling mechanism and a wrist locking feature. After describing the mechanisms and its kinematic configuration, we report on a comparative study under controlled conditions, developed to measure the end effector orientation in both compensated and non-compensated scenarios. The results demonstrate that the compensated master console maintains a near constant end effector orientation over the workspace during clutching, showing great promise as a solution to this outstanding open challenge in master-slave manipulation.

Mobile Manipulators (MM) has attracted a lot of researchers for incorporation in the robotics field owning to their multitude of applications in real world. Welding automation has its wide applications in industry like automobile manufacturing and power generation industry involving spherical tanks. The objective of this study is to design workspace and devise a methodology to plan position trajectory of welding tool that produces smooth welding while the mobile platform turns simultaneously. The robot proposed in this paper has the manipulator mounted on a platform moving as a turntable to increase the workspace and enhances the mobility of the manipulator. The earlier produces linear segment of weld while the later produces parabolic segment. The kinematic equations for mobile platform and the mounted manipulator are described in detail. The workspace of the robot is visualized based on computations of transformation matrices and jacobians structured based on kinematic equation. Trajectories for each joint, computed using inverse kinematic equations, are also presented. For spherical trajectories the solution of system equations is combined with constraint values for each manipulator joint, thus allowing computation of desired joint position at any time interval. The efficacy of the proposed methodology for the trajectory planning is tested through a case study. The simulation results of motion transformation, workspace and trajectory show that linear segments of the trajectory combine with parabolic trajectory segments smoothly with zero acceleration within designed reachable workspace. The experimental results verify the efficacy of application of presented kinematic and inverse kinematic models for welding of spherical objects.

This paper presents a novel motion planner for redundant robotic manipulators by utilizing rapidly exploring randomized trees and artificial potential fields. Rapidly exploring randomized trees and artificial potential fields are two well-known navigational strategies in the robotics industry; however, their potential benefits and synergy when implemented together has been largely unexplored. In the proposed motion planner, rapidly exploring randomized trees is first used to determine a suitable path for the end-effector to follow that maneuvers around all obstacles in the robot’s workspace. Once a path has been determined, attractive and repulsive potential fields are implemented at all points along the path and are used in a gradient optimization algorithm to determine joint trajectories to reach the desired location. To supplement the attractive and repulsive potential fields, an orientation field is proposed to minimize the error between the actual end-effector orientation and the desired orientation during joint trajectory planning. The motion planner is examined through both analytical and experimental evaluation using the 7 degrees of freedom Kinova JACO and Kinova Gen3 robotic arms. The conclusions drawn from this work substantiate the efficacy and superiority of the proposed two-stage motion planner for the control of redundant manipulators in obstacle-ridden environments.

This paper discusses a postprocessor for milling robots connected to additional linear machine axes where toolpath is optimized with respect to variable properties of the robot in its workspace. A toolpath optimization method is proposed based on an experimentally verifiedrobot stiffness model. After postprocessor distribution of the movements between the robot and the linear axes, the collision states during machiningcannot be verified in common CAM. Therefore, a solution enabling simulation of movements after optimization is proposed. The tool center point coordinates are used to control the robot and additional machine axes, while the joint coordinates calculated by inverse kinematic transformation are used to verify the movements.

This paper presents a nonlinear control approach based on backstepping techniques for a high-speed linear axis driven by pneumatic artificial muscles (PAMs). Its guided carriage is actuated by a nonlinear drive system consisting of two pulley tackles with PAMs mounted at both sides. This allows for an increased workspace as well as higher carriage velocities as compared to a direct actuation. The proposed control scheme has a cascaded structure, where backstepping control concepts are used for a fast inner pressure control loop as well as an outer position control. Hysteresis of the PAMs is not modelled directly but counteracted by an additional adaptive parameter in the outer control loop. The main contribution of this paper is the investigation of a self-tuning algorithm that optimises the controlled system behaviour. Based on several criteria, the gradient of an evaluation cost function (ECF) w.r.t. the control design parameters is approximated and used for an optimisation. Two different variants of the self-tuning adaptive backstepping control are compared with each other using realistic simulations of a given test rig. The obtained results show an excellent closed-loop performance after tuning – compared with the initial design.