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This article provides a detailed comparative analysis of five orientational, two degrees of freedom (DOF) mechanisms whose envisioned application is the wrist of the iCub humanoid robot. Firstly, the current iCub mk.2 wrist implementation is presented, and the desired design objectives are proposed. Prominent architectures from literature such as the spherical five-bar linkage and spherical six-bar linkage, the OmniWrist-III and the Quaternion joint mechanisms are modeled and analyzed for the said application. Finally, a detailed comparison of their workspace features is presented. The Quaternion joint mechanism emerges as a promising candidate from this study.

Background: It is a challenge to reduce the muscular discoordination in the paretic upper limb after stroke in the traditional rehabilitation programs.Method: In this study, a neuromuscular electrical stimulation (NMES) and robot hybrid system was developed for multi-joint coordinated upper limb physical training. The system could assist the elbow, wrist and fingers to conduct arm reaching out, hand opening/grasping and arm withdrawing by tracking an indicative moving cursor on the screen of a computer, with the support from the joint motors and electrical stimulations on target muscles, under the voluntary intention control by electromyography (EMG). Subjects with chronic stroke (n = 11) were recruited for the investigation on the assistive capability of the NMES-robot and the evaluation of the rehabilitation effectiveness through a 20-session device assisted upper limb training.Results: In the evaluation, the movement accuracy measured by the root mean squared error (RMSE) during the tracking was significantly improved with the support from both the robot and NMES, in comparison with those without the assistance from the system (P < 0.05). The intra-joint and inter-joint muscular co-contractions measured by EMG were significantly released when the NMES was applied to the agonist muscles in the different phases of the limb motion (P < 0.05). After the physical training, significant improvements (P < 0.05) were captured by the clinical scores, i.e., Modified Ashworth Score (MAS, the elbow and the wrist), Fugl-Meyer Assessment (FMA), Action Research Arm Test (ARAT), and Wolf Motor Function Test (WMFT).Conclusions: The EMG-driven NMES-robotic system could improve the muscular coordination at the elbow, wrist and fingers.Trial Registration: ClinicalTrials.gov. NCT02117089 ; date of registration: April 10, 2014. [ABSTRACT FROM AUTHOR]

Haptic exploration has received a great deal of attention of late thanks to the variety of commercially available tactile sensors. While the majority of previous works consider control of a single contact point at a time, we tackle simultaneous control of multiple contact points on several links. In addition, we use information from the existing tactile signals to increase the number of points in contact. We demonstrate the usefulness of this form of control to speed up exploration, scanning and to compliantly grasp unknown objects. Our controller requires to know only the parts of the robot on which it is desirable to make contact and does not need a model of the environment besides the robot itself. We validate the algorithm in a set of experiments using a robotic hand covered with tactile sensors and arm. In a grasping application, the active adaptation of the fingers to the shape of the object ensures that the hand encloses the object with multiple contact points. We show that this improves the robustness of the grasp compared to simple enclosing strategies. When combined with an exploration strategy, our multi-contact approach offers an efficient use of tactile sensors on the whole surface of robotic fingers, and enables the robot to perform a rapid exploration of complex, non convex shapes while maintaining low contact forces. It is robust to variation in the approach angle and to changes in the geometry and orientation of the object. [ABSTRACT FROM AUTHOR]

The use of precision actuators in robotic arm comes from the need to ensure the resulting accuracy of the robot at the maximum speed of movement. The replacement of actuators by means of electrical module allows the use of carrier body of the module for gripping flanges or other modules. Development of new modules is based on the requirement of providing a complete solution for the customer's needs. After the development of new modules, the producer checks the parameters, receives feedback, and uses the authentication options in the independent workplaces, which can provide impartial results. Based on this data, manufacturers can optimize their solutions and deliver the products to market, complying with not only their vision but mainly the needs of customers. This article describes how to verify the characteristics of the modules used in the construction of robotic wrist. It primarily focuses on verification of the accuracy of results and repeatability of position of the wrist on output flange end module. In addition, it presents the design of the testing stand and selection methodologies of measurement. The declared values are compared with the values measured during verification. [ABSTRACT FROM AUTHOR]

As an underactuated mechanism, the accuracy analysis of the spherical 3 degrees of freedom (3-DOF) parallel underactuated robot wrist becomes an important issue. However, current researches in the accuracy analysis always focus on the full-actuated mechanism. In this paper, the loop incremental method is applied to the accuracy analysis of the spherical 3-DOF parallel underactuated robot wrist. After the novel underactuated robot wrist is introduced, this paper presents the loop selection rules. According to the above rules, four loops are selected from the underactuated robot wrist. After error model of each loop is proposed, the error model of the underactuated robot wrist, including both position error and orientation error, is then established by the loop incremental method. After the accuracy analysis of the underactuated robot wrist is verified with the experiments on coordinate measuring machine, the robot wrist is then guided to be assembled with the minimum global error. The result is testified to demonstrate that the methodology is helpful for robot design. [ABSTRACT FROM AUTHOR]

The workspace denotes the work area of a robot, which is an important foundation of designing a robot. As formulating the suitable workspace models for a robot wrist is very crucial for analyzing its behavior, many researches have been focused on it in recent decades with a result of many valuable contributions. However, current researches always focus on rigid and full actuated robot wrist, while the robot wrist is always a multibody system, which can affect the accuracy of workspace analysis and simulation. This paper proposed a model of workspace analysis of a novel underactuated robot wrist based on virtual prototyping. After the conceptual design of a novel underactuated mechanism was introduced, the degree of freedom of the underactuated robot wrist was calculated. Then the detailed design of underactuated robot wrist was done. The whole workspace model of the robot system was then established. It was indicated that the working points in the workspace of the robot were distributed compactly and uniformly, which can meet design requirements with high efficiency. The workspace analysis of underactuated robot wrist and the accuracy analysis of underactuated robot wrist were also put forward. The result was testified by the simulation on Matlab, which demonstrated that the methodology is obviously helpful for robot design. [ABSTRACT FROM AUTHOR]

Compact rehabilitation robot system which can support movement of the wrist of patients has been developed. The robot system can detect and analyze the patient's intention to move the wrist by such a biological signal as muscle potential, then, assist the wrist exercise of patients. Also, both-wrist rehabilitation robot system by mirror effect has been successfully developed for practical use in the hospital and at home. [ABSTRACT FROM AUTHOR]

The article discusses a study on the use of artificial tactile feedback to increase the ability of a paralyzed patient to manipulate objects through 1a brain-controlled robotic arm, published in within the issue of "Science". Topics discussed include ways to restore sensory feedback to the brain, an improvement in the movement time for a patient to grasp an object, and the implications of the study for advancement of robotics and development of tactile artificial skins.

Abstract: The work reported here pertains to the low-frequency dynamic analysis of the testbed for a novel gearless pitch-roll wrist (PRW). The testbed is excited with harmonic inputs that produce periodic responses of the multiple-input multiple-output system. The input–output data measured are then processed to identify damping and stiffness values of the flexible components of the testbed. The inertial parameters are computed from the 3D CAD model of the mechanism. The paper highlights a novel approach of averaging the response data in order to obtain the best parameter estimates of the linear mechanical system under test. [Copyright &y& Elsevier]

The articles in this special issue focus on the development and applications supported by assistive robotics in the services industry with particular emphasis on medical robtoics. [ABSTRACT FROM AUTHOR]

Assistive robotics is an increasingly popular research field, which has led to a large number of commercial and noncommercial systems aimed at assisting physically impaired or elderly users in the activities of daily living. In this article, we propose five criteria based on robotic arm usage scenarios and surveys with which assistive robotic arms can be classified. Different possibilities and implementations to obtain each criterion are treated, and examples of current assistive robotic arms are given. Implementations and systems are discussed and rated qualitatively, which leads to the observation that variable stiffness actuation offers great benefits for assistive robotic systems despite an increase in the overall complexity. [ABSTRACT FROM AUTHOR]

To improve the dynamic characteristic of two-axis force sensors, a dynamic compensation method is proposed. The two-axis force sensor system is assumed to be a first-order system. The operation frequency of the system is expanded by a digital filter with backward difference network. To filter high-frequency noises, a low-pass filter is added after the dynamic compensation network. To avoid overcompensation, parameters of the proposed dynamic compensation method are defined by trial and error. Step response methods are utilized in dynamic calibration experiments. Compared to experiment data without compensation, the response time of the dynamic compensated data is reduced by 30%~40%. Experiments results demonstrate the effectiveness of our method. [ABSTRACT FROM AUTHOR]

This paper presents a wearable exoskeleton upper limb rehabilitation robot that consists of eight active joints and one passive joint. Each active joint is driven by two pneumatic muscles (PMs) in opposing pair configuration and each PM drives the joint through a steel wire with a flexible sleeve and a tension device. These factors incorporate with characteristics of PM make the rehabilitation robot system very complex (nonlinear, time-varying, and time-delay). In this paper, the friction force and characteristics of open-loop control of one of the robotic joints has been studied. The quasi-static model of the robotic joint have been established based on experimental methods. In addition, the performances of three control modes have also been researched. These works would be helpful to the future work such as the control of the rehabilitation robot. [ABSTRACT FROM AUTHOR]

Abstract: A robotic wrist has been developed for physicians to perform ultrasound imaging on patients located at remote sites. Detailed design, kinematic analysis, prototyping, and preliminary clinical tests of the wrist are reported in this paper. The wrist has certain characteristics which make it novel from mechanical point of view and with respect to its suitability for ultrasound imaging. It is a four degree-of-freedom device and uses parallel mechanisms in its configuration to provide a remote center-of-motion. All four actuators are located on the ground, and each actuator is responsible for one required motion of the ultrasound probe. The wrist has been prototyped. Successful remote ultrasound imaging of kidney and liver has been done on a few volunteers to show the applicability of the proposed device. [Copyright &y& Elsevier]

This paper describes quick and stable standing and sitting motion of an inverted pendulum type robot by whole-body motion including force control. The whole-body motion is achieved by controlling composite center of gravity of the robot, and damping force control of a wrist-roller is employed to assure the stability of inverted pendulum control on a contact situation with the ground. Motion planning of standing and sitting based on the proposed control method is also proposed. Standing and sitting motion using the proposed motion control and motion planning is simulated with a dynamic simulator, ODE (Open Dynamics Engine). From the simulation results, it was confirmed that the robot successively realized the standing and sitting motion quickly and stably. [ABSTRACT FROM AUTHOR]

Human characteristics are supposed to be applied to the control systems of the human-friendly robots. Therefore, it is important to know the human characteristics in human-robot cooperative tasks. In this study, we considered a single rotational degree of freedom experimental system as well as a mass-spring-damper-friction dynamic model for the human arm, measured the torque acting on the armload from subject's forearm and the angular displacement of subject's forearm using the force sensor and the eddy current sensor, analyzed their mutual relation, and attained the characteristics of the human arm with the effect of the gravity load. We compared this cooperative motion to that studied without the gravity load and found that the damping and friction characteristics remained unchanged and the spring characteristics disappeared. In this case, the characteristics of the follower's arm had no relationship with the weight of the load. [ABSTRACT FROM AUTHOR]

A robot manipulator control method using an electromyogram (EMG) from a human face is proposed. The robot has a three-degree-of-freedom arm with an end effector installed on the tip of the robot. The amplitude of the EMG signal generated from the masseter, a jaw muscle, is used to control the robot hand velocity and to grasp the object. The difference of the EMG level between right and left masseter determines the hand's direction of movement. The open-close control of the robot hand is activated by detecting double clenches performed within 0.6 s. Low-pass filters of two kinds are applied to the measured EMG to enable reliable and effortless control of the velocity and grasping task. Picking, transferring, and placing of a brick object are performed. The effectiveness of the proposed method was verified. [ABSTRACT FROM AUTHOR]

Anatomical data acquisition methods used within medicine exhibit various strengths and weaknesses, particularly with regards to accuracy, resolution, patient comfort and safety. Difficulties with data acquisition of wrist and hand geometry are often underestimated, and a suitable method is yet to be identified and standardised to capture skin surface topography to support the mass customisation of wrist splints. The aim of this investigation is to identify a suitable data acquisition method, capable of digitising collected data of the wrist and hand, for manipulation and conversion into a suitable file format to create customised wrist splints using additive manufacturing. Literature suggests that scanning inanimate objects such as plaster casts using multiple three-dimensional laser scanners can provide adequate quality scans with suitable accuracy and resolution, with low cost and low risk to the patient. However, post processing would be required to create a 'watertight' digital model suitable for additive manufacturing. [ABSTRACT FROM AUTHOR]

The increasing demand for physical interaction between humans and robots has led to an interest in robots that guarantee safe behavior when human contact occurs. However, attaining established levels of performance while ensuring safety creates formidable challenges in mechanical design, actuation, sensing and control. To promote safety without compromising performance, a human-friendly robotic arm has been developed using the concept of hybrid actuation. The new design employs high-power, low-impedance pneumatic artificial muscles augmented with small electrical actuators, distributed compact pressure regulators with proportional valves, and hollow plastic links. The experimental results show that significant performance improvement can be achieved with hybrid actuation over a system with pneumatic muscles alone. In this paper we evaluate the safety of the new robot arm through experiments and simulation, demonstrating that its inertia/power characteristics surpass those of previous human-friendly robots we have developed. [ABSTRACT FROM AUTHOR]

Feedforward controller would be useful for hybrid Functional Electrical Stimulation (FES) system using powered orthotic devices. In this paper, Feedback Error Learning (FEL) controller for FES (FEL-FES controller) was examined using an inverse statics model (ISM) with an inverse dynamics model (IDM) to realize a feedforward FES controller. For FES application, the ISM was tested in learning off line using training data obtained by PID control of very slow movements. Computer simulation tests in controlling wrist joint movements showed that the ISM performed properly in positioning task and that IDM learning was improved by using the ISM showing increase of output power ratio of the feedforward controller. The simple ISM learning method and the FEL-FES controller using the ISM would be useful in controlling the musculoskeletal system that has nonlinear characteristics to electrical stimulation and therefore is expected to be useful in applying to hybrid FES system using powered orthotic device. [ABSTRACT FROM AUTHOR]

A hybrid control scheme based on adaptive visual servoing and direct force control is proposed for robot manipulators to perform interaction tasks on smooth surfaces. The camera parameters, as well as the constraint surface, are considered to be uncertain. A fixed camera with optical axis non-perpendicular to the robot workspace is used for position control, while a force sensor mounted on the robot wrist is used for force regulation. In order to solve the interaction problem on unknown surfaces, a method is developed to estimate the constraint geometry and keep the end-effector orthogonal to the surface at the contact point, during the task execution. Experimental results are presented to illustrate the performance and feasibility of the proposed scheme. [ABSTRACT FROM AUTHOR]

This paper presents the design, control and performance of a high fidelity four degree-of-freedom wrist exoskeleton robot, Rice Wrist, for training and rehabilitation. The Rice Wrist is intended to provide kinesthetic feedback during the training of motor skills or rehabilitation of reaching movements. Motivation for such applications is based on findings that show robot-assisted physical therapy aids in the rehabilitation process following neurological injuries. The exoskeleton device accommodates forearm supination and pronation, wrist flexion and extension and radial and ulnar deviation in a compact parallel mechanism design with low friction, zero back/ash and high stiffness. As compared to other exoskeleton devices, the Rice Wrist allows easy measurement of human joint angles and independent kinesthetic feedback to individual human joints. In this paper joint-space as well as task-space position controllers and an impedance-based force controller for the device are presented. The kinematic performance of the device is characterized in terms of its workspace, singularities, manipulability, backlash and backdrivability. The dynamic performance of Rice Wrist is characterized in terms of motor torque output, joint friction, step responses, behavior under closed loop set-point and trajectory tracking control and display of virtual walls. The device is singularity-free, encompasses most of the natural workspace of the human joints and exhibits low friction, zero-backlash and high manipulability, which are kinematic properties that characterize a highquality impedance display device. In addition, the device displays fast, accurate response under position control that matches human actuation bandwidth and the capability to display sufficiently hard contact with little coupling between controlled degrees-of-freedom. [ABSTRACT FROM AUTHOR]

The article discusses the intelligent robotic system named Deep Green. This system has been developed to play pool and currently performs above amateur level with the ultimate goal of having the robot compete against a human opponent. Deep Green is a 3-degree-of-freedom (DOF) industrial gantry robot, with a 3-DOF spherical robot wrist, that has been mounted to the ceiling so it doesn't get in the way of others using the pool table. It also has attached a digital camera global vision system with directional lights and an "end-effector" which includes two cue devices, one on a linear electromagnetic motor allowing strikes of a velocity of 3 meters per second, and a pneumatic cue used for power breaks up to a velocity of 12 m/s.

This paper presents the NEURARM, a novel robotic platform specifically designed for performing joint experiments between neuroscience and robotics. The NEURARM replicates the main functions and characteristics of the human arm during the execution of planar movements for reaching and catching a moving object. The NEURARM is a 2-d.o.f. planar robotic platform actuated by means of four linear hydraulic actuators and four cables integrated in agonist–antagonist configuration. The first version of a non-linear spring that will be integrated in series with the actuator has been developed and tested. The main components of the sensory system are four tension sensors on the cables, two angle sensors in the joints, and linear potentiometers and pressure sensors on the pistons. The paper presents the design methodology, the developed components and system, and the experimental characterization of the NEURARM. The available data demonstrate qualitatively that the design is appropriate, that the NEURARM is able to replicate the required maximum kinematics performance and that real joint experiments with neuroscientists can start. [ABSTRACT FROM AUTHOR]

A novel approach to antagonism in robotic systems is introduced and investigated as the basis for an unequalled, highly anthropomorphic hand–arm system currently being developed. This hand–arm system, consisting of a 19-d.o.f. hand and a 7-d.o.f. flexible arm, will be based on antagonistic principles in order to study and mimic the human musculoskeletal system, as well as to advance safety in robotics. [ABSTRACT FROM AUTHOR]

A novel 6 degrees of freedom (DOFs) wearable exoskeleton arm, ZJUESA, based on man-machine system is presented. It can be used in robot bilateral teleoperation as master arm with force-feedback. With introducing the revolute-prismatic-spherical (RPS) parallel mechanism and planetary gear mechanism, it is designed based on the anatomy of human upper-limb. With the sensors on this external mechanical structure, the human operator motion is detected and converted to the slave robot control command. Additionally the pneumatic system on it generates a force feedback by using hybrid fuzzy control. As a result, the human operator may have a feeling of doing the work directly. [ABSTRACT FROM AUTHOR]

Iterative learning control (ILC) is applied to a robot arm with joint flexibility. The ILC algorithm uses an estimate of the arm angle, where the estimate is computed using measurements of the motor angle and the arm angular acceleration. The design of the ILC algorithm is evaluated experimentally on a laboratory scale robot arm with good results. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes a method to modify the dynamics of single-link flexible arms in order to allow the design of a control system which is more robust to changes in the payload value. This is achieved by attaching some small lumped masses at some points of the link. Therefore, connections between the dynamics and the feedforward control of single-link flexible manipulators are considered to simplify the control and make the system faster and more robust. The feedforward controller design is based on the so-called dynamic model inversion technique derived from a discretization of the system dynamic model. A comparative assessment between the discrete model inversion based on feedforward control and the command preshaping technique is presented. Numerical examples and experimental results thus changing the payload values are carried out. [Copyright &y& Elsevier]

The Omni-Wrist III robotic manipulator. Inspired in design by the kinematics of the human wrist, represents, with the full 1800 hemisphere of singularity-free range, a very capable alternative to traditional gimbals systems. Research efforts at the Laser Communications Research Laboratory at Binghamton University have resulted in the establishment of an accurate mathematical model, which was utilized in the development of control systems presented in this paper. A state variable controller and two linear model following controllers are developed and evaluated. The third controller is designed to achieve full decoupling of the highly coupled system. The adaptation and disturbance rejection capabilities of the controllers are demonstrated through friction compensation. [ABSTRACT FROM AUTHOR]

A spherical gear is a mechanism for transferring motion. This type of gear has more than one direction of freedom, so it is very suitable for a flexible robot wrist. In general, spherical gear mechanisms have two degrees of freedom. Thus, from a geometric viewpoint, a mathematical derivation for producing a spherical gear with discrete ring-involute teeth is a conjugate problem. A rack-cutter that distributes ring teeth on a plane generates the spherical gear. Based on the envelope theory of a two-parameter family of rack-cutter surfaces, mathematical and geometric models of a spherical gear with discrete ring-involute teeth are proposed. Using CAD software, a geometric model of a spherical gear can be assembled. The developed spherical gear transmission has a gear ratio that is not 1, and an example is provided to demonstrate the double DOF transmission ratio of 4:3. [ABSTRACT FROM AUTHOR]

Grasping force optimization with nonlinear friction constraints is a fundamental problem in dextrous manipulation with multifingered robotic hands. Over the last few years, by transforming the problem into convex optimization problems on Riemannian manifolds of symmetric and positive definite matrices, significant advances have been achieved in this area. Five promising algorithms: two gradient algorithms, two Newton algorithms, and one interior point algorithm have been proposed for real-time solutions of the problem. In this paper, we present in a unified geometric framework, the derivation of these five algorithms and the selection of step sizes for each algorithm. Using the geometric structure of the affine-scaling vector fields associated with the optimization problem, we prove that some of these algorithms have quadratic convergence properties, and their continuous versions are exponentially convergent. We evaluate the performance of these algorithms through simulation and experimental studies with the Hong Kong University of Science and Technology (HKUST) three-fingered hand. This study will facilitate selection and implementation of grasping force optimization algorithms for similar applications. [ABSTRACT FROM AUTHOR]

The article outlines an evolutionary account relating motivational systems to emotions and the cortical systems which elaborate them. It then addresses the issue of whether and how to characterise emotions in such a way that one might say that a robot has emotions even if they are not empathically linked to human emotions. [ABSTRACT FROM AUTHOR]

This paper presents closed-form solutions for the inverse and direct dynamic models of the Gough-Stewart parallel robot. The models are obtained in terms of the Cartesian dynamic model elements of the legs and of the Newton-Euler equation of the platform. The final form has an interesting and intuitive physical interpretation. The base inertial parameters of the robot, which constitute the minimum number of inertial parameters, are explicitly determined. The number of operations to compute the inverse and direct dynamic models are given. [ABSTRACT FROM AUTHOR]

Among the new architectures for parallel wrists, recently presented in the literature, one of the simplest Is the architecture of the 3-revolute-spherical-revolute (RSR) wrist. The kinematics of the 3-RSR wrist has not been presented yet, in the literature. This paper presents the kinematic analysis of the 3-RSR wrist. In particular, the demonstration that the 3-RSR wrist makes the end-effector perform finite spherical motion is reconsidered from a different point of view. The new demonstration directly provides the constraint singularities of the 3-RSR wrist. Moreover, the position analysis of the 3-RSR wrist is reduced to the solution of problems already solved in the literature. Finally, the mobility analysis of the 3-RSR wrist is addressed, and all its singularity conditions are found in analytical form and geometrically interpreted. [ABSTRACT FROM AUTHOR]

The static analysis of a parallel wrist, known as the 3-universal-prismatic-universal (UPU) wrist, is presented, and the 3-UPU wrist singularity conditions ire interpreted from a statics point of view. An equation (singularity equation) that enables fluffing all the 3-UPU wrist singular configurations is written in explicit form. Moreover, the use of the Rodrigues parameters to parameterize the 3-UPU wrist platform orientation allows the singularity equation to become a fourth-degree polynomial equation in three unknowns. Finally, a numerical example is presented. [ABSTRACT FROM AUTHOR]

This paper proposes a method of acquisition of a page turning skill for a multifingered robotic hand using reinforcement learning. The goal of this paper is generation of the manipulation skill of a flexible object without its explicit model and tactile sensation during its control. In this paper, a page turning task is considered as an example of such tasks, where a sheet of paper, generally used in books, is a flexible object. The fingertip trajectories are obtained by reinforcement learning based on simulation. The reward considering a friction condition is given, so that a page turning skill without slip between the finger and the paper is obtained. The validity is confirmed by an experimental system which consists of a 2-d.o.f. manipulator and two 2-d.o.f. fingers. [ABSTRACT FROM AUTHOR]

Based on the analysis of the stiffness relation between the operational space and the fingertip space of multi-fingered hands, this paper provides a guideline of task-based compliance planning for multi-fingered robotic manipulations. In order to show the characteristics of the taskbased stiffness matrix, various two- and three-dimensional examples are illustrated. Also, it is shown that some of the coupling stiffness elements cannot be planned arbitrarily due to grasping geometry. Through the analytical results, it is concluded that the operational stiffness matrix should be carefully specified by considering the location of the compliance center and the grasp geometry of multifingered hands for successful grasping and manipulation tasks. [ABSTRACT FROM AUTHOR]

This paper discusses a novel assembly method and system for a commercially available 8 mm diameter miniature planetary gearhead. Our system comprises a commercially available four-degree of freedom industrial robot, two vision systems, a force feedback system in the robot wrist, and specially designed flexible part feeders. The system has proved successful in assembling planetary gear units independently. Depending on the task, one can select whether to use the high accuracy and repeatability of the robot or alternatively use programmable frequency vibration in the gripper to stochastically align the parts that the robot handles. [ABSTRACT FROM AUTHOR]

In this paper, the physical model of the solution space of spherical 3-DOF serial wrists is established. The reachable workspaces are classified. The dexterous workspaces for such wrists are investigated based on the rotatability conditions for the spherical 4-bar mechanism. Using the theory of conformal transformation, we obtain plane figures of the reachable and dexterous workspaces. The atlases of the workspaces in the physical model of the solution space are plotted. These results are useful not only for designer overall to understand the relationship between the workspaces and link lengths of spherical 3-DOF serial wrists, but also for the design of the wrists. [ABSTRACT FROM AUTHOR]

The idea of the multi-controller approach is to design local controllers, each of them combined with a special environment. One problem of this approach is to select the best local controller or even several controllers in order to design the final control law, which will be applied to the plant. In this paper, a 'switching' algorithm based on a symbolic fuzzy system is used. The main goal is basically to blend the control signals provided by several controllers, which are modelreference output feedback controllers (RST controllers) in our method. Nonetheless, an interesting issue is the stability of the global structure with a reference signal. In this paper, we present research studies on the stability analysis of the proposed multi-controller approach by using Lyapunov theory and linear matrix inequalities (LMIs). The derivative of a candidate quadratic Lyapunov function is calculated thanks to a weighted sum of local derivatives. Finally, a real-time experimentation on a robot wrist shows the effectiveness of the approach. [ABSTRACT FROM AUTHOR]

A clamped–free flexible arm rotating in a horizontal plane and carrying a moving mass is studied in this paper. The arm is modelled by the Euler–Bernoulli beam theory in which rotatory inertia and shear deformation effects are ignored. The assumed mode method in conjunction with Hamilton''s principle is used to derive the equation of motion of the system which takes into account the effect of centrifugal stiffening due to the rotation of the beam. The eigenfunctions of a cantilever beam which satisfy the prescribed geometric boundary conditions are used as basis functions in the assumed mode method. The equation of motion is expressed in non-dimensional matrix form. Pre-designed transformed cosine profiles are used as trajectory inputs for the hub angle and the moving mass. The equation of motion is solved numerically using the fourth order Runge–Kutta method. Graphical results are presented to show the influence of centrifugal stiffening effect, moving mass values, mass travelling time, hub angle and mass trajectory profile on the deflection of the beam. [Copyright &y& Elsevier]

The direct position analysis of the fully parallel spherical wrist with general geometry can have up to eight poses for a given set of leg lengths. This paper presents a procedure that makes use of one extra rotary sensor, suitably located in the wrist (in addition to the three linear sensors embedded in the leg servosystems) to enable the actual pose of the spherical wrist to be uniquely defined and the wrist direct position analysis to be computed in real time. Closed-form solution of the direct position analysis is obtained, which makes it possible to refine the measurement provided by the extra sensor and consequently to improve the robustness of the procedure. Examples are reported that show the efficiency of the procedure. © 2001 John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In this paper, a new kinematic model of the human wrist is developed and compared to existing robot wrists. A detailed analysis of the motion of the involved carpus bones indicates the position and orientation of the motion axes. Approximations are made to approach a technical feasible model, on the one hand, but to preserve functional characteristics on the other hand. For the mathematical description, screw theory and the product-of-exponentials method are applied. Characteristic parameters of the model are identified and quantitative values for a typical person proposed. Finally, similarities between existing robot wrists and the model are discussed. © 2001 John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Parallel manipulators are constituted of two rigid bodies, one movable (platform) and the other fixed (base), connected by a number of kinematic chains (legs). Manipulators with all equal legs that have the actuators adjacent to the base allow the use of simplified design procedures and manufacturing processes. Moreover, they are able to reach high performances. Further manufacturing simplifications can be obtained if only revolute pairs and passive cylindrical pairs are used. This article presents a new spherical parallel manipulator, named the 3-URC wrist. The 3-URC wrist is not overconstrained. It has three equal legs having only passive cylindrical pairs and revolute pairs with the actuators adjacent to the base. The 3-URC wrist mounting and manufacturing conditions making spherical motions of the platform possible are defined. Then the position analysis and the mobility analysis of the 3-URC wrist are solved. Finally, the singularity conditions are written in explicit form and geometrically interpreted. © 2001 John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This paper presents the design of a robot wrist with zero hand length and unlimited mutually orthogonal joints. This design is an improvement over existing ones. When equipped with this type of wrist, a robot's entire reachable workspace becomes the dexterous workspace. Because some wrist joint limitations may need to be imposed under practical consideration, to better assess this new wrist design, kinematics on robot point accessibility is derived. An algorithm and a software package are developed that enable the plotting of the point accessibility throughout the robot's entire workspace. Examples for demonstration are also included. [ABSTRACT FROM AUTHOR]

Highlights the principles of human-humanoid interaction employed in the Intelligent Soft-Arm Control (ISAC) robotics system. Outline of the software architecture of ISAC; Decomposition of the system into a set of atomic agents; Types of atomic agents.

Shows that a passive robotic wrist, of mixed mechanical design, can be programmed to execute a wide range of force-control laws useful in automated assembly. Synthesis of joint-space matrices; Sensitivity analysis of the task-space accommodation matrices; Use of task-space variables to describe a matrix suitable for a given task.