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Electromyographic prosthesis with higher degrees of freedom is an expanding area of research. In this paper, active prosthesis with four degrees of freedom has been investigated, which can be used to fit a limb with amputation below elbow. The system comprises of multichannel inputs which correspond to the flexion and extension as well as supination and pronation. To find maximum surface neural activity, accurate placement of electrodes has been carried out on 10 subjects aged between 22-30 years. Signals (0-500 hertz) acquired from contracting voluntary muscles with minimum cross talk and common mode noise. Clean filtered EMG signal is then amplified precisely. Finally digitization is being done to drive bionic hand. Practical demonstration on a simple DC motor proved providential using this method for the two motions of an actual human arm. EMG Signals emanating from muscles dedicated to individual fingers have been recorded. Moreover modern classifiers; KNN and NN have been investigated carefully with selected features through different time and noise levels.

Concreteness is central to theories of learning in psychology and organizational behavior. However, the literature provides many competing measures of concreteness in natural language. Indeed, researcher degrees of freedom are often large in text analysis. Here, we use concreteness as an example case for how language measures can be systematically evaluated across many studies. We compare many existing measures across datasets from several domains, including written advice, and plan-making (total N = 9,780). We find that many previous measures have surprisingly little measurement validity in our domains of interest. We also show that domain-specific machine learning models consistently outperform domain-general measures. Text analysis is increasingly common, and our work demonstrates how reproducibility and open data can improve measurement validity for high-dimensional data. We conclude with robust guidelines for measuring concreteness, along with a corresponding R package, doc2concrete, as an open-source toolkit for future research.

Normal alkane is an unbranched alkane whose structural formula is H-CH2-CH2-⋯-CH2-⋯-CH2-H, which can be regarded as a reconfigurable chain-type structure composed of -CH2- modules. Inspired by normal alkane, a normal-alkane-like re-configurable modular robot (NAR) is proposed. The module consists of two differential gear trains mounted orthogonally. Each differential gear train contains two input degrees of freedom and two output degrees of freedom. Due to the genderless interface design, multiple modules can be assembled into chain-type configuration. With the genderless interfaces and flexible degrees of freedom, NAR can be reconfigured into different dimensions of spatial configuration. The bond matrix is used to describe the configuration, which represents the bond attitude of the adjacent connected modules. In addition, full interconnected geometric feature (FIGF) algorithm is proposed for non-isomorphic configuration enumeration and judgment. The configurations with three modules are simulated and the results verify the feasibility of the algorithm. Finally, a prototype with three modules is fabricated and the configuration motion sequence is demonstrated.

In this study, a new rigid–flexible gear with metal rubber is proposed to reduce the vibration of the gear transmission system. A nonlinear dynamic model with nine degrees of freedom considering bearing clearance, gear backlash, surface friction, and time-varying meshing stiffness is established. The nondimensional dynamic model of the transmission system is obtained and the bifurcation characteristics of the new rigid–flexible gear pair and the rigid gear pair are analyzed when the damping coefficient is, respectively, 0.03 and 0.1. The result shows that the motion state of the rigid–flexible gear pair is more stable. The dynamic responses of the rigid gear pair and the rigid–flexible gear pair are compared as well through numerical analysis and experiment to illustrate the advantage of the rigid–flexible gear pair in vibration reduction. The results can provide reference for vibration reduction of the novel gear transmission.

Improved ergonomics for the operating surgeon may be an advantage of robotic colorectal surgery. Perceived robotic ergonomic advantages in visualisation include better exposure, three-dimensional vision, surgeon camera control, and line of sight screen location. Postural advantages include seated position and freedom from the constraints of the sterile operating field. Manipulation benefits include articulated instruments with seven degrees of freedom movement, elimination of fulcrum effect, tremor filtration, and scaling of movement. Potential ergonomic detriments of robotic surgery include lack of haptic feedback, visual, and mental strain from increased operating time and interruptions to workflow from crowding.

Three-dimensional (3D) printing, also known as additive manufacturing (AM), has emerged in the last decades as an innovative technology to build complex structures. It enables increasing design complexity and low-cost customization with a vast range of materials. AM capabilities contributed to a widespread acceptance of 3D printing in different industries such as the aerospace and the automotive. However, important issues and limitations still need to be addressed, namely in printing complex objects where supports and material roughness surface are to be minimized. In this work we consider a 5–axis printer with the three traditional xyz movements and two additional degrees of freedom on the printer table bed. These extra degrees of freedom (table bed rotation and tilt) allow printing of more complex objects, and we propose an approach which consists on the decomposition of complex objects into simpler parts, allowing each part to be printed in an optimal way. We aim to reduce the number of supports needed and attain high final object quality due to lower material surface roughness. The optimal printing direction (or, equivalently, rotation) and sequencing of the object parts is determined by solving a combinatorial sequencing optimization problem. All the local or global optimal parts rotations are obtained by solving a global optimization sub-problem for each part, and are taken as input parameters for the sequencing optimization problem. We provide a heuristic approach for the combinatorial sequencing optimization problem, and a multistart multisplit search methodology for computing all the local or global optimal parts rotations for the sub-problems.

Physicians use pain expressions shown in a patient's face to regulate their palpation methods during physical examination. Training to interpret patients’ facial expressions with different genders and ethnicities still remains a challenge, taking novices a long time to learn through experience. This letter presents MorphFace: a controllable 3D physical-virtual hybrid face to represent pain expressions of patients from different ethnicity-gender backgrounds. It is also an intermediate step to expose trainee physicians to the gender and ethnic diversity of patients. We extracted four principal components from the Chicago Face Database to design a four degrees of freedom (DoF) physical face controlled via tendons to span $\sim\!85\%$ of facial variations among gender and ethnicity. Details such as skin colour, skin texture, and facial expressions are synthesized by a virtual model and projected onto the 3D physical face via a front-mounted LED projector to obtain a hybrid controllable patient face simulator. A user study revealed that certain differences in ethnicity between the observer and the MorphFace lead to different perceived pain intensity for the same pain level rendered by the MorphFace. This highlights the value of having MorphFace as a controllable hybrid simulator to quantify perceptual differences during physician training.

Unlike fixed-base offshore wind turbine, the soft floating platform introduces 6 more degrees of freedom of motions to the floating offshore wind turbine. This may cause much more complex inflow environment to the wind turbine rotors compared with fixed-base wind turbine. The wind seen locally on the blade changes due to the motions of the floating wind turbine platform which has a direct impact on the aerodynamic condition on the blade such as the angle of attack and the inflow velocity. Such unsteady aerodynamic effects may lead to high fluctuation of the loads and power output. The present work aims to study the high unsteady aerodynamic performance of the floating wind turbine under platform surge motion. The unsteady aerodynamic loads are predicted with a lifting surface method with a free wake model. A preview predict control algorithm is used as the pitch control strategy. A full scale U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) 5 MW floating wind turbine is chosen as the subject of the present study. The unsteady aerodynamic performance and instabilities have been discussed in detail under prescribed platform surge motions with different control targets. Both minimizing the power output and rotor thrust fluctuation are set as the control objectives respectively. The theory analysis and the simulation results indicate that the blade pitch control can effectively alleviate the variation of the rotor thrust under platform surge motions. Larger amplitude of the variation of blade pitch is needed to alleviate the variation of the wind turbine power and this leads to high rotor thrust fluctuation. It is also shown that negative damping can be achieved during the blade pitch control process and may lead the floating platform wind turbine system into unstable condition.

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.

In this paper, a method to determine optimal adjustment trajectories for the loading and unloading phases of heavy plate levelers is proposed. Due to the high leveling forces, the elastic structure of the leveler is deformed. The available adjustment possibilities of the machine are typically used to actively compensate for the deflection of its work rolls. However, only a small subset of the available degrees of freedom of the leveler may be controlled under load. Therefore, the optimal adjustment is typically determined for the highest expected load and uniformly applied during the whole leveling process. As a consequence, the deflection is overcompensated during the loading and unloading phases of the plate and the head and tail ends of the plate might develop ski-ends. To avoid such an overcompensation, the adjustable degrees of freedom of the leveler can be used. Based on an accurate deflection model of the leveler, the loading and unloading phases of the plate are simulated and the input trajectories for the adjustable degrees of freedom of the leveler are optimized. The proposed approach is validated with simulations.

Automatic multiple geographical feature label placement (MGFLP) is a combinatorial optimization problem shown to be an NP-hard problem, and it is a challenge in automatic cartography. Many automatic label placement algorithms for point, line, and area features were put forward. It is a common way to use multiple candidate positions (MCP) for label placement, but the research in this way mostly focuses on point features and does not take all three types of features and all the possible candidate positions into account on the map. Therefore, in this paper, the concept of degrees of spatial freedom for feature label placement is proposed based on the idea of degrees of freedom of mechanical motion. We define the degrees of freedom (DOF) and its space for feature labels on a planar map so as the potential space, including all the optional candidate positions of each feature label, can be standardized. Based on two degrees of freedom (2-DOF) space, feature reference position (FRP), and certain buffer distance (CBD) from FRP, we studied the methods including generating, calculating, evaluating, and selecting MCP for feature label. By using and improving the discrete differential evolution genetic algorithm (DDEGA), we carried out MGFLP experiments on the same dataset used by DDEGA algorithm. The results show that: 1) although the MCP based on the 2-DOF space increase the complexity of the NP-hard problem, however, the obtained results by optimizing the performance of the algorithm and increasing the number of candidate positions are still better than the traditional 8-candidate positions model. 2) In the same 2-DOF space, increasing the candidate positions from less to more along each direction of the 2-DOF space improves the quality of label placement.

This paper is about the design and analysis of two different rocket nozzle configurations. First configuration is without any fillets and curved surfaces and second configuration is with fillets and curved surfaces. Second configuration is used since stress concentration will be more at the corners if we don’t have an optimized geometry having suitable fillets at appropriate places. Radiuses of fillets are chosen by previous studies conducted by academicians and design scientists for optimized configurations which give less overall induced stress values and hence more life. Initial configuration and Optimized configuration were drawn in ANSYS Mechanical APDL 14.5 and coupled element Quad 8 node 223 was selected for analysis. Material selected was Ti6Al4V (Grade 5). Quadrilateral mapped meshing was done and suitable boundary conditions were applied with the help of AXIMER 1.0 software. Different plots were obtained for Degrees of Freedom solution, Stress, Thermal Flux, Thermal Gradient and Total Thermal and Mechanical Strains for the two configurations. The degrees of freedom solution is calculated for all active degrees of freedom in the model, which are determined by the union of all degrees of freedom labels associated with all the active element types. It can be controlled and in this case, it would give the total number of degrees of freedom in every element of the model. Compared the two configurations and explained why the second configuration is better than the first.

This paper analyzes the optimal communication involving large intelligent surfaces (LIS) starting from electromagnetic arguments. Since the numerical solution of the corresponding eigenfunctions problem is in general computationally prohibitive, simple but accurate analytical expressions for the link gain and available spatial degrees-of-freedom (DoF) are derived. It is shown that the achievable DoF and gain offered by the wireless link are determined only by geometric factors, and that the classical Friis' formula is no longer valid in this scenario where the transmitter and receiver could operate in the near-field regime. Furthermore, results indicate that, contrarily to classical MIMO systems, when using LIS-based antennas DoF larger than 1 can be exploited even in strong line-of-sight (LOS) channel conditions, which corresponds to a significant increase in spatial capacity density, especially when working at millimeter waves., Comment: Presented in part at thge IEEE International Conference on Communications (ICC), 2020. In publication on IEEE Journal on Selected Areas in Communications, Special issue on Wireless Networks Empowered by Reconfigurable Intelligent Surfaces, 2020 (IEEE JSAC, Nov 2020)

Recent advances in speech technologies have produced new tools that can be used to improve the performance and flexibility of speaker recognition While there are few degrees of freedom or alternative methods when using fingerprint or iris identification techniques, speech offers much more flexibility and different levels for performing recognition: the system can force the user to speak in a particular manner, different for each attempt to enter. Also with voice input the system has other degrees of freedom, such as the use of knowledge/codes that only the user knows, or dialectical/semantical traits that are difficult to forge. This paper offers and overview of the state of the art in speaker recognition, with special emphasis on the pros and contras, and the current research lines. The current research lines include improved classification systems, and the use of high level information by means of probabilistic grammars. In conclusion, speaker recognition is far away from being a technology where all the possibilities have already been explored., 7 pages. arXiv admin note: text overlap with arXiv:2202.11459

The complex degrees of freedom of light, such as amplitude, phase, polarization, and orbital angular momentum, make it a prime candidate for use in optical security and encryption. By exploiting the unique characteristics of metasurfaces, exciting new optical security platforms have been demonstrated.

In this brief opinionated article, I present a personal perspective on metamterials with high degrees of freedom and dimensionality and discuss their potential roles in enriching light–matter interaction in photonics and related fields.

In a typical optical test, a stereo camera pair is required to measure the three-dimensional motion of a test article; one camera typically only measures motions in the image plane of the camera, and measurements in the out-of-plane direction are missing. Finite element expansion techniques provide a path to estimate responses from a test at unmeasured degrees of freedom. Treating the case of a single camera as a measurement with unmeasured degrees of freedom, a finite element model is used to expand to the missing third dimension of the image data, allowing a full-field, three-dimensional measurement to be obtained from a set of images from a single camera. The key to this technique relies on the mapping of finite element deformations to image deformations, creating a set of mode shape images that are used to filter the response in the image into modal responses. These modal responses are then applied to the finite element model to estimate physical responses at all finite element model degrees of freedom. The mapping from finite element model to image is achieved using synthetic images produced by a rendering software. The technique is applied first to a synthetic deformation image, and then is validated using an experimental set of images.

The article considers innovative directions of development of forest and agricultural machinery with intelligent control systems. The kinematics is considered on the example of a harvester with a multi-link manipulator and walking running equipment. Systems of equations describing the spatial position of working and running equipment with a large number of degrees of freedom are presented. The assessment of existing problems and development prospects is given.

This paper proposes a new single master bimanual teleoperation (SMBT) system with an efficient position, orientation and force regulation strategy. Unlike many existing studies that solely support motion synchronization, the first contribution of the proposed work is to propose a solution for orientation regulation when several slave robots have differing motions. In other words, we propose a solution for self-regulated orientation for dual-arm robots. A second contribution in the paper allows the master with fewer degrees of freedom to control the slaves (with higher degrees of freedom), while the orientation of the slaves is self-regulated. The system further offers a novel force regulation that enables the slave robots to have a smooth and balanced robot-environment interaction with proper force directions. Finally, the proposed approach provides adequate force feedback about the environment to the operator and assists the operator in identifying different motion situations of the slaves. Our approach demonstrates that the forces from the slaves will not interrupt the operator’s perception of the environment. To validate the proposed system, experiments are conducted using a platform consisting of two 7-Degree of Freedom (DoF) slave robots and one 3-DoF master haptic device. The experiments demonstrated good results in terms of position, orientation and force regulation., This work was supported by Autonomous Intelligent Systems for Enterprise and Exploration (AI.MEE) program: AUTODIVE, and the Knowledge Foundation (www.kks.se) under the scope of the AMICI Project: Augmented Interaction for Human-Robot Collaborative Tasks in Industrial Environments.

This work deals with an analysis of the acceleration level to which a patient is exposed during ambulance transportation. A dynamic analysis of ambulance movements has been approached considering some different operating conditions of the vehicle, such as braking, driving over speed bumps and on uneven pavements. The purpose of this study is providing sources for development of a system reducing vibration effects on the body when a patient is transported by ambulance.

Neural question generation (NQG) is the task of generating questions from the given context with deep neural networks. Previous answer-aware NQG methods suffer from the problem that the generated answers are focusing on entity and most of the questions are trivial to be answered. The answer-agnostic NQG methods reduce the bias towards named entities and increasing the model's degrees of freedom, but sometimes result in generating unanswerable questions which are not valuable for the subsequent machine reading comprehension system. In this paper, we treat the answers as the hidden pivot for question generation and combine the question generation and answer selection process in a joint model. We achieve the state-of-the-art result on the SQuAD dataset according to automatic metric and human evaluation.

Understanding the processes underlying sensorimotor coupling with the environment is crucial for sensorimotor rehabilitation and sensory substitution. In doing so, devices which provide novel sensory feedback consequent to body movement may be optimized in order to enhance motor performance for particular tasks. The aim of the study reported here was to investigate audio-motor coupling when the auditory experience is linked to movements of the head or the hands. The participants had to localize and reach a virtual source with the dominant hand in response to sounds. An electromagnetic system recorded the position and orientation of the participants’ head and hands. This system was connected to a 3D audio system that provided binaural auditory feedback on the position of the virtual listener located on the participants’ body. The listener’s position was computed either from the hands or from the head. For the hand condition, the virtual listener was placed on the dominant hand (the one used to reach the target) in Experiment 1 and on the non-dominant hand, which was constrained in order to have similar amplitude and degrees of freedom as that of the head, in Experiment 2. The results revealed that, in the two experiments, the participants were able to localize a source within the 3D auditory environment. Performance varied as a function of the effector’s degrees of freedom and the spatial coincidence between sensor and effector. The results also allowed characterizing the kinematics of the hand and head and how they change with audio-motor coupling condition and practice.

Increasing automation of road-bound vehicles will lead to autonomous, driverless vehicle concepts. Although vehicle manufacturers are showing visions of such concepts, their design process is still not largely researched. New degrees of freedom will not only eliminate the driver’s workplace, but will also make it possible to pursue secondary activities. Thus, an investigation is needed to determine which customer-relevant properties can be used to describe autonomous vehicle concepts. We present a method to address the new degrees of freedom. The method begins with a definition of the customer structure and leads to the vehicle concept. We also make a proposal for customer-relevant properties of autonomous vehicle concepts. For this, two expert surveys, first expert interviews and second an expert workshop, were conducted and connected with knowledge from the literature. The result is a portfolio of twelve whole vehicle properties. We assert that the developed method with the identified costumer-relevant properties can become the basis for the adaptation of the automotive product development process to autonomous vehicles.

In this paper, we propose a combination of discrete elements for the soil and finite elements for the fluid flow field inside the pore space to simulate the triggering of landslides. We give the details for the implementation of third order finite elements (“P2 with bubble”) together with polygonal discrete elements, which allows the formulation with a minimal number of degrees of freedom to save computer time and memory. We verify the implementation with several standard problems from computational fluid dynamics, as well as the decay of a granular step in a fluid as test case for complex flow.

In this paper, one class of single-input single-output (SISO) X networks with cache at both transmitters and receivers is considered. Specifically, the X networks consist of two transmitters and K receivers. Furthermore, only the delayed channel state information at transmitters (CSIT) is available. In order to improve degrees of freedoms (DoF) of the system, we propose a cache-aided retrospective interference alignment (RIA) scheme which contains the Prefetching Phase and the Delivery Phase. In the Prefetching Phase, we carefully choose the contents to be cached at both transmitters and receivers. In the Delivery Phase, we propose a cache-aided RIA transmission scheme where order-μ symbols are delivered and the cached contents are exploited to cancel interference. Moreover, when μ = K - 1, it is reduced to a blind scheme, which does not need the CSIT. Furthermore, we present one theorem to characterize the sum DoF of the proposed cache-aided RIA scheme. It is shown that the proposed cache-aided scheme outperforms the RIA scheme without cache and the cache-aided interference management scheme for the system configuration considered in this paper.

In this paper, a novel information leakage resistant quantum dialogue (QD) protocol with single photons in both polarization and spatial-mode degrees of freedom is proposed, which utilizes quantum encryption technology to overcome the information leakage problem. In the proposed QD protocol, during the transmission process, the single photons in both polarization and spatial-mode degrees of freedom used for encoding two communicants' private classical bits are protected by both quantum encryption technology and decoy photon technology. For avoiding the information leakage problem, the initial states of the single photons in both polarization and spatial-mode degrees of freedom used for encoding two communicants' private classical bits are shared between two communicants through quantum key encryption and decryption. The information-theoretical efficiency of the proposed QD protocol is as high as 40%., Comment: 7 pages

This study presents a method to improve vehicle ride comfort using additional damping coefficient values for an internal combustion engine (ICE) rubber mounting system. To analyze the effect of the adding damping coefficient values into the rubber mounting system on vehicle ride comfort, a full-vehicle vibration model with 10 degrees of freedom is established under the combination of road surface roughness and ICE excitations. The damping coefficient values are added into ICE rubber mounting system which are respectively analyzed and evaluated according to the international standard ISO 2631-1 (1997). The study results do not only evaluate the influence of the adding damping coefficients on vehicle ride comfort but also suggest the optimal design solution for ICE mounting system to improve vehicle ride comfort.

In recent years, the field of psychology has begun to conduct replication tests on a large scale. Here, we show that “replicator degrees of freedom” make it far too easy to obtain and publish false-negative replication results, even while appearing to adhere to strict methodological standards. Specifically, using data from an ongoing debate, we show that commonly exercised flexibility at the experimental design and data analysis stages of replication testing can make it appear that a finding was not replicated when, in fact, it was. The debate that we focus on is representative, on key dimensions, of a large number of other replication tests in psychology that have been published in recent years, suggesting that the lessons of this analysis may be far reaching. The problems with current practice in replication science that we uncover here are particularly worrisome because they are not adequately addressed by the field’s standard remedies, including preregistration. Implications for how the field could develop more effective methodological standards for replication are discussed.

In Internet of Things (IoT) environments, visual sensors with good performance have been used to create and apply various kinds of image data. Particularly, in the field of human–computer interaction, the image sensor interface using human hands is applicable to sign language recognition, games, object operation in virtual reality, and remote surgery. With the popularization of depth cameras, there has been a new interest in the research conducted in RGB images. Nevertheless, hand pose estimation is hard. Research on hand pose estimation has multiple issues, including high-dimensional degrees of freedom, shape changes, self-occlusion, and real-time condition. To address the issues, this study proposes the random forests-based method of hierarchically estimating hand pose in depth images. In this study, the hierarchical estimation method that individually handles hand palms and fingers with the use of an inverse matrix is utilized to address high-dimensional degrees of freedom, shape changes, and self-occlusion. For real-time execution, random forests using simple characteristics are applied. As shown in the experimental results of this study, the proposed hierarchical estimation method estimates the hand pose in input depth images more robustly and quickly than other existing methods.

Background Prosthetic restoration of reach and grasp function after a trans-humeral amputation requires control of multiple distal degrees of freedom in elbow, wrist and fingers. However, such a high level of amputation reduces the amount of available myoelectric and kinematic information from the residual limb. Methods To overcome these limits, we added contextual information about the target’s location and orientation such as can now be extracted from gaze tracking by computer vision tools. For the task of picking and placing a bottle in various positions and orientations in a 3D virtual scene, we trained artificial neural networks to predict postures of an intact subject’s elbow, forearm and wrist (4 degrees of freedom) either solely from shoulder kinematics or with additional knowledge of the movement goal. Subjects then performed the same tasks in the virtual scene with distal joints predicted from the context-aware network. Results Average movement times of 1.22s were only slightly longer than the naturally controlled movements (0.82 s). When using a kinematic-only network, movement times were much longer (2.31s) and compensatory movements from trunk and shoulder were much larger. Integrating contextual information also gave rise to motor synergies closer to natural joint coordination. Conclusions Although notable challenges remain before applying the proposed control scheme to a real-world prosthesis, our study shows that adding contextual information to command signals greatly improves prediction of distal joint angles for prosthetic control.

Heterogenous networks are mainly limited by interference. Nowadays, the advances in reconfigurable antennas allow us to implement blind interference alignment (BIA) schemes, which avoid the need for channel state information at the transmitter (CSIT) while providing an increasing multiplexing gain, i.e., the achievable DoF, as the number of users increases. In this work, we propose a downlink transmission scheme based on BIA for managing the inter-tier interference in K -tier networks, referred to as tier BIA (tBIA). The tBIA scheme can be implemented considering that each tier employs any BIA scheme for managing the intracell and intercell interference. In this sense, considering proper BIA schemes applied to each tier, tBIA fully cancels all the sources of interference. After that, the DoF outer-bound for K -tier networks without CSIT is derived. It is shown that tBIA reaches this outer-bound. Furthermore, it is demonstrated that fully managing the inter-tier interference provides larger DoF in the whole network than turning off any tier with the aim of improving the achievable DoF in the remaining tiers. Simulation results show that the proposed tBIA scheme provides greater DoF and improves the user rates in comparison with other schemes without CSIT in multi-tier networks. This work has been supported by project IRENEEARTH (PID2020-115323RB-C33 / AEI / 10.13039/501100011033) and the project GEOVEOLUZ-CM-UC3M has been funded by the call "Programa de apoyo a la realización de proyectos interdisciplinares de I+D para jóvenes investigadores de la Universidad Carlos III de Madrid 2019-2020" under the frame of the Convenio Plurianual Comunidad de Madrid-Universidad Carlos III de Madrid.

Locomotion in humans and animals is highly coordinated, with many joints moving together. Learning similar coordinated locomotion in articulated virtual characters, in the absence of reference motion data, is a challenging task due to the high number of degrees of freedom and the redundancy that comes with it. In this paper, we present a method for learning locomotion for virtual characters in a low dimensional latent space which defines how different joints move together. We introduce a technique called motor babble, wherein a character interacts with its environment by actuating its joints through uncoordinated, low-level (motor) excitations, resulting in a corpus of motion data from which a manifold latent space is extracted. Dimensions of the extracted manifold define a wide variety of synergies pertaining to the character and, through reinforcement learning, we train the character to learn locomotion in the latent space by selecting a small set of appropriate latent dimensions, along with learning the corresponding policy.

If we think about plug-in hybrids, the treatment of paravalvular leaks in cardiac surgery may not be the first thing that comes to mind. Yet, there appears to be an attractive analogy between the plug in hybrid car and an interventional device that may be "plugged in" intra-operatively to treat a paravalvular leak. Both technologies provide additional degrees of freedom to the fields, combine different technologies but may also be criticized for their increase in cost, introduction of new problems and their questionable practical need. We address this analogy based on a case series presented in this issue of the Journal of Cardiac Surgery.

Myoelectric signals allow to control prostheses and exoskeletons intuitively and effectively by estimating movement intention from the activation of multiple muscles. However, not all muscle activation patterns generate movements, because of the redundancy of the musculoskeletal system. Therefore, such “null space” activations could be used to control extra degrees-of-freedom while simultaneously performing a task. Here, we tested the feasibility of this approach by instructing participants to match the position and orientation of an ellipsoidal target by displacing and rotating an ellipsoidal cursor through the generation of isometric force and electromyographic null space activation. Participants were able to perform the task and their performance improved with practice. However, there was a large variability across participants in their ability to hold the cursor within the target. These results support the feasibility of null space control and suggest that task difficulty must be optimized according to the individual control ability.

The control architecture guiding simple movements such as reaching toward a visual target remains an open problem. The nervous system needs to integrate different sensory modalities and coordinate multiple degrees of freedom in the human arm to achieve that goal. The challenge increases due to noise and transport delays in neural signals, non-linear and fatigable muscles as actuators, and unpredictable environmental disturbances. Here we examined the capabilities of hierarchical feedback control models proposed by W. T. Powers, so far only tested in silico. We built a robot arm system with four degrees of freedom, including a visual system for locating the planar position of the hand, joint angle proprioception, and pressure sensing in one point of contact. We subjected the robot to various human-inspired reaching and tracking tasks and found features of biological movement, such as isochrony and bell-shaped velocity profiles in straight-line movements, and the speed-curvature power law in curved movements. These behavioral properties emerge without trajectory planning or explicit optimization algorithms. We then applied static structural perturbations to the robot: we blocked the wrist joint, tilted the writing surface, extended the hand with a tool, and rotated the visual system. For all of them, we found that the arm in machina adapts its behavior without being reprogrammed. In sum, while limited in speed and precision (by the nature of the do-it-yourself inexpensive components we used to build the robot from scratch), when faced with the noise, delays, non-linearities, and unpredictable disturbances of the real world, the embodied control architecture shown here balances biological realism with design simplicity., This work was supported by the Spanish Ministry of Science (pre-doctoral contract BES-2016-077608 to AM; Severo Ochoa of Excellence program SEV-2013-0317 start-up funds to AG-M; Ramón y Cajal grant RyC-2017-23599 to AG-M).

Distance-based motion adaptation leads to the formulation of a dynamical Distance Geometry Problem (dynDGP) where the involved distances simultaneously represent the morphology of the animated character, as well as a possible motion. The explicit use of inter-joint distances allows us to easily verify the presence of joint contacts, which one generally wishes to preserve when adapting a given motion to characters having a different morphology. In this work, we focus our attention on suitable representations of human-like animated characters, and study the advantages (and disadvantages) in using some of them. In the initial works on distance-based motion adaptation, a 3n-dimensional vector was employed for representing the positions of the n joints of the character at a given frame. Here, we investigate the use of another, very popular in computer graphics, representation that basically replaces every joint position in the three-dimensional space with a set of three sorted Euler angles. We show that the latter can in fact be useful for avoiding some of the artifacts that were observed in previous computational experiments, but we argue that this Euler-angle representation, from a motion adaptation point of view, does not seem to be the optimal one. By paying particular attention to the degrees of freedom of the studied representations, it turns out that a novel character representation, inspired by representations used in structural biology for molecules, may allow us to reduce the character degrees of freedom to their minimal value. As a result, statistical analysis on human motion databases, where the motions are given with this new representation, can potentially provide important insights on human motions. This study is an initial step towards the identification of a full set of constraints capable of ensuring that unnatural postures for humans cannot be created while tackling motion adaptation problems.

Continuum robots with redundant degrees of freedom and postactuated devices are suitable for application in aerospace, nuclear facilities, and other narrow and multiobstacle special environments. The development of a snake-inspired continuum robot is presented in this study. The morphological skeleton structure of the snake body is simulated using underactuated continuum joints, which include several rigid-body joints in series. Each rigid-body joint is driven by the traction of a wire rope. Based on the layered-drive principle, angular synchronous motion can be realized in space with multiple rigid-body joints in a single continuous joint, which can considerably reduce the complexity of the inverse kinematics solution, terminal drive box, and control system. The static and dynamic characteristics of the snake-inspired robot are obtained through torque balance and an equivalent transformation. Finally, we demonstrate trajectory planning and load capacity testing in two robot prototypes with arm lengths of 1500 and 2300 mm (including two and four continuous joints, respectively). The rationality of the structure and the correctness of the control of the layered-drive snake-inspired robot are verified.

Prosthesis design has an influence on the quantity and quality of postoperative motion after cervical disc arthroplasty. Prostheses with built-in resistance to angular and translational motion may have an advantage in restoring physiologic motion. The ability of a prosthesis to work with remaining bony and soft tissues to restore motion and load-sharing is a function of the kinematic degrees of freedom DOF, axis of rotation for a given motion, and device stiffness. How these characteristics allow the prosthesis to work with the patient's anatomy will determine whether the prosthesis is successful at restoring motion and mitigating adjacent-level stresses.

Virtual object manipulation as a key feature has been studied in virtual reality (VR) environments. Previous studies highlighted user experience on three basic types of virtual object manipulation, translation, rotation and scaling. However, prior literature mainly studied task performance in manipulation modes with different degrees of freedom (DoF), and few studies assessed user experience by evaluating the psychological response, such as mental workload on these three basic manipulation types in virtual environments. This paper compared manipulation modes with 1DoF and 3DoF to assess users’ mental workload as a critical indicator of user experience by electroencephalogram (EEG) measurement and questionnaires in manipulation tasks on the webpage with VR effects (also known as WebVR). By applying signal processing and statistical methods to analyze EEG data from ten subjects, the results demonstrated that the participants generally perceive less mental workload by 1DoF manipulation modes than 3DoF on WebVR. Besides, this study also found some different results between objective and subjective data.

Η παρούσα διδακτορική διατριβή πραγματεύεται την κατασκευή και τον έλεγχοκαινοτόμων ρομποτικών συστημάτων με στόχο την εφαρμογή τους σε ελάχισταεπεμβατικές, ρομποτικά υποβοηθούμενες, χειρουργικές επεμβάσεις. Τα συστή-ματα που κατασκευάστηκαν για το σκοπό αυτό φέρουν πληθώρα καινοτόμων χα-ρακτηριστικών με τα βασικότερα να αποτελούν τους αυξημένους βαθμούς ελευ-θερίας σε σχέση με υπάρχοντα εμπορικά συστήματα, τη δομοστοιχειωτή φύση,τη φορητότητα, την εύκολη αλλαγή χειρουργικών εργαλείων, το χαμηλό κόστος,καθώς και το ανοιχτού πηγαίου κώδικα υποστηρικτικό λογισμικό τους. Ειδικότερα, τα υλοποιηθέντα ρομποτικά συστήματα αποτελούνται από έξω-επεμβατικούς βαθμούς ελευθερίας που επιτρέπουν την εισχώρηση στην χειρουρ-γική κοιλότητα και έσω-επεμβατικούς βαθμούς ελευθερίας, ώστε να καθοδηγη-θούν μικροσκοπικά ιατρικά εργαλεία στο σημείο ενδιαφέροντος. Η κατασκευήέγινε με μεθόδους ταχείας προτυποποίησης και με παραμετρικά εκφρασμένα δο-μικά χαρακτηριστικά, οδηγώντας σε δομοστοιχειωτού χαρακτήρα ρομπότ. Ένας σημαντικός παράγοντας που συντελεί στην επίτευξη των ανωτέρω και-νοτομιών είναι η χρήση μορφομνήμονων κραμάτων νικελίου-τιτανίου για τηνενεργοποίηση των αρθρώσεων των έσω-επεμβατικών βαθμών ελευθερίας. Τακράματα αυτά, παρά τη δυσκολία στον έλεγχό τους, δίνουν την δυνατότητα ναμειωθεί αισθητά το βάρος των κατασκευών, ενώ παράλληλα εγγυώνται βιοσυμβα-τότητα και μελλοντική πιθανή χρήση σε περιβάλλον μαγνητικού τομογράφου. Ταηλεκτρονικά κυκλώματα που υλοποιήθηκαν για την οδήγηση των βαθμών ελευθε-ρίας ενσωματώνονται στο ρομπότ και επιτρέπουν την ανάδραση θέσης από τουςπροαναφερθέντες ενεργοποιητές. Στο άκρο των ρομποτικών βραχιόνων τοποθετείται, πέραν του κατ' επιλογήχειρουργικού εξοπλισμού, στερεοσκοπική κάμερα και φωτισμός, ώστε να είναιεφικτή η οπτικοποίηση σε μικρή απόσταση του σημείου αλληλεπίδρασης με τονιστό. Η κύρια επέκταση της συγκεκριμένης δομής είναι ότι δεν απαιτείται πλέονη χρήση δεύτερης οπής για εισχώρηση ενδοσκοπίου, πράγμα πολύ σημαντικό γιατον χρόνο αποκατάστασης και τη χρονική διάρκεια των χειρουργικών επεμβά-σεων. Ο έλεγχος των ρομποτικών συστημάτων γίνεται με χρήση κατάλληλων εύκολαεπεκτάσιμων αλγορίθμων, ενώ παράλληλα έχει αναπτυχθεί κατάλληλο λογισμικόεκμάθησης, οπτικοποίησης της θέσης και προ-εγχειρητικής καταχώρησης επιθυ-μητών θέσεων. Ο χειρισμός των συστημάτων γίνεται με χρήση συσκευών απτικήςανάδρασης. Τα συστήματα αξιολογούνται τόσο όσον αφορά την αυτονομία τους, όσο καισε κλασικά ενδοσκοπικά πειράματα, ώστε να είναι δυνατή η εξαγωγή συμπερα-σμάτων αναφορικά με την λειτουργικότητά και την δυνατότητα κλινικής εφαρμο-γής τους.

The race for the 6G has started, and new exciting ideas on 6G antennas are on the table. This contribution gives a look to the 6G ideas from a novel angle of view, the Deep Physical Layer (DPL), a layer added at the very botton level of the OSI stack, in which the analysis is carried out at the electromagnetic field level. It is suggested that the performance of the communication system can be quantified using the space-time Number of Degrees of Freedom (ST-NDF), allowing a simple comparison among the different solutions.

We provide a review of our results on the design of mantle cloaking devices for antenna applications with an emphasis on our recent investigations in designing advanced cloaking metasurfaces. It is shown how such cloaking devices allow increasing the degrees of freedom in the design of conventional antennas with a significant enhancement of their functionalities. Several examples of antennas whose conventional functionalities are enriched using cloaking metasurfaces loaded with electronic circuits are reported, and the most significant applications in view of a new generation of intelligent antennas are discussed.

Since the quadruped bionic robot can be widely applied to different terrains, the research on it has always been the focus of robotics-related field. This paper designs a quadruped bionic robot with 8 degrees of freedom. We analyze stability and movement speed of the robot in different gaits. The gait focuses on crawl in triangular gait and trot in diagonal gait. In the case of using 8 degrees of freedom (two per leg), through gait analysis, 3D modeling, physical testing and using larger sole to improve stability, the designed quadruped robot can achieve stable and fast movement.

This paper presents the kinematic modeling and design of deployable structures inspired by pop-up books. These pop-up structures can exhibit large changes in area and volume through deployment motion that resembles opening the pages of a book. The pop-up structures have a modular topology and are formed by multiple parallelepiped units, here termed as pop-up units. The analysis of the kinematics of single pop-up units and assemblies of these that form larger structures is presented. An algorithm that integrates multiple pop-up units to form structures that approximate two-dimensional and three-dimensional target shapes when deployed is subsequently devised. The algorithm ensures that the structures formed by the assemblies of multiple pop-up units retain the single degree of freedom of a pop-up unit. The stored strain energy of these structures, which can provide the means to deploy them in practice, is also analyzed. Finally, various examples showing the applicability of the design algorithm in the synthesis of pop-up structures that approximate a diverse set of two-dimensional and three-dimensional target shapes are provided. The pop-up structures can be applied to a large spectrum of applications that need extensive deployment from small volumes while requiring a low number of degrees of freedom. These applications may include aerospace structures and MEMS.

This paper presents structures with multiple equilibrium configurations arising from the combination of a state of prestress and unilateral contacts. A design problem is posed where preloaded elastic springs and unilateral constraints are embedded throughout a mechanism. The spring parameters are designed such that multiple target configurations are immobilized due to contact. In each of these configurations, the spring forces maintain compressive reaction forces, immobilizing the structure. Each immobilized configuration can rigidly resist perturbation forces up to some finite magnitude where contact is lost. Hence, this case of multiple configurations in equilibrium due to the combination of prestress and contact is referred to as multi-configuration rigidity. Two examples of structures exhibiting multi-configuration rigidity are presented. First, a four bar linkage with a single kinematic degree of freedom is used to introduce the concept. In the context of the linkage, multi-configuration rigidity is compared to multi-stability, exhibiting the key differences between the two concepts. Then, a 24-degree-of-freedom kirigami surface is presented that can morph between flat and spherical configurations, motivated by RF antenna applications. By embedding torsional springs and fold angle stops throughout the structure, flat and spherical configurations are made rigid. Actuation between the configurations can easily be achieved by snapping the structure between the rigid configurations.

Herein, we have confirmed the importance of formulating product proposals and product-development processes equipped to cope effectively with uncertainty in the early design stage. The objective of this study was to derive the target performance and design priority order taking into account uncertainties in system design. Following the concept of set-based design, the approach adopted was to secure a set of solutions as design space that satisfy the target variables demands, dividing the design space into several clusters and evaluating each of the clusters, then gradually narrowing the cluster as the design progresses, and finally extracting the solution space that is desirable. Priority order of design was developed based on the strategy of increasing the degree of freedom of the subsequent process. The effectiveness of the proposed method was verified using the model of a plug-in hybrid vehicle. From the results, we confirmed the existence of a trade-off between design and target variables preference and development risk, that it is possible to determine the extent to which the solution space can be narrowed, that the shape of the solution space determines the design priorities, and we were able to derive a desirable design priority order according to the target performance.

The traditional locomotion paradigm of quadruped robots is to use dexterous (multi degrees of freedom) legs and dynamically optimized footholds to balance the body and achieve stable locomotion. With the introduction of a robotic tail, a new locomotion paradigm becomes possible as the balancing is achieved by the tail and the legs are only responsible for propulsion. Since the burden on the leg is reduced, leg complexity can be also reduced. This paper explores this new paradigm by tackling the dynamic locomotion control problem of a reduced complexity quadruped (RCQ) with a pendulum tail. For this specific control task, a new control strategy is proposed in a manner that the legs are planned to execute the open-loop gait motion in advance, while the tail is controlled in a closed-loop to prepare the quadruped body in the desired orientation. With these two parts working cooperatively, the quadruped achieves dynamic locomotion. Partial feedback linearization (PFL) controller is used for the closed-loop tail control. Pronking, bounding, and maneuvering are tested to evaluate the controller’s performance. The results validate the proposed controller and demonstrate the feasibility and potential of the new locomotion paradigm.

In this paper, we present the design of a pneumatically actuated skeleton for a robotic fish. The tail is designed as a one degree of freedom coiling truss that is actuated by air pressure supplied to pouch actuators along the truss. We present that kinematic synthesis procedure, the fabrication and testing of the fish tail system. Our goal is an efficient and effective fish-like locomotion system.