This work describes a systematic methodology for the synthesis of tendon-driven manipulators. A method for enumerating the topology of tendon routings is first established. To conform with the enumerated structures, the kinematic synthesis of the manipulator using singular value decomposition is then developed. Design equations for synthesizing a general tendon-driven manipulator with isotropic transmission characteristics are subsequently derived. It is shown that the design methodology may give designers wider selection in determining the tendon routing topology than prior methods by other literature.

This paper proposes a control scheme for the teleoperation of a mobile robot in presence of time delay. Our proposal uses a compensation of the time delay based on a human operator's model and a simple 3D augmented reality scheme; both are related through a prediction system. Unlike other strategies, the proposed scheme has a model of the human operator inside it, including his decision so that human and robot “push in the same direction.” The stability of the teleoperation system adding the proposed control scheme is proven concluding how the time delay changes the convergence rate and the convergence ball size. Finally, to illustrate the performance and stability of the proposed control structure, several teleoperation experiments in presence of various delays are shown.

This paper shows that a well-known causal PD controller plus feedforward solves the global output feedback tracking control problem of robot manipulators, by requiring only the existence of the robot natural damping, no matter how small. To this end, we first demonstrate that a robot controlled by a causal PD is globally input-to-state stable (ISS) with respect to a bounded input disturbance. Then, we prove that the addition of a feedforward compensation renders the error system uniformly globally asymptotically stable. Furthermore, we present a possible extension to more general nonlinear systems and also to uncertain systems.

Dynamic simulation in robotic systems can be considered as a useful tool not only for the design of both mechanical and control systems, but also for planning the tasks of robotic systems. Usually, the dynamic model suffers from discontinuities in some parts of it, such as the use of Coulomb friction model and the contact problem. These discontinuities could lead to stiff differential equations in the simulation process. In this paper, we present an algorithm that solves the discontinuity problem of the Coulomb friction model without applying any normalization. It consists of the application of an external switch that divides the integration interval into subintervals, the calculation of the friction force in the stick phase, and further improvements that enhance its stability. This algorithm can be implemented directly in the available commercial integration routines with event-detecting capability. Results are shown by a simulation process of a simple 1-DoF oscillator and a 3-DoF parallel robot prototype considering Coulomb friction in its joints. Both simulations show that the stiffness problem has been solved. This algorithm is presented in the form of a flowchart that can be extended to solve other types of discontinuity.

In this paper, an interactive virtual reality motion simulator is designed and analyzed. The main components of the system include a bilateral control interface, networking, a virtual environment, and a motion simulator. The virtual reality entertainment system uses a virtual environment that enables the operator to feel the actual feedback through a haptic interface as well as the distorted motion from the virtual environment just as s/he would in the real environment. The control scheme for the simulator uses the change in velocity and acceleration that the operator imposes on the joystick, the environmental changes imposed on the motion simulator, and the haptic feedback to the operator to maneuver the simulator in the real environment. The stability of the closed-loop system is analyzed based on the Nyquist stability criteria. It is shown that the proposed design for the simulator system works well and the theoretical findings are validated experimentally.

This paper considers a problem of tracking control design for different types of nonholonomic mobile manipulators. The mobile platform is in form of a unicycle. In the first step, an input–output decoupling controller is developed. The proposed selection of output functions is in more general form than the output functions previously introduced by others [Yamamoto and Yun]. It makes possible to move simultaneously, the mobile platform and the manipulator built on it. Regularity conditions that guarantee the existence of the input–output decoupling control law are presented. In the second step, trajectory and path tracking controllers are formulated and presented. Theoretical considerations are illustrated with simulations for the mobile manipulator consisting of a vertical, three degree of freeedom (DOF) pendulum (with holonomic or nonholonomic drives) mounted atop of a unicycle.

This paper describes a project that aims to demonstrate two-way communication between robots using chemical signals. The project is part of a wider investigation examining the potential advantages and drawbacks of implementing pheromone signalling between robots. It is well known that all kinds of biological creatures use chemicals as a means of attracting, repelling, controlling, guiding and informing their fellow creatures. This very wide range of effective biological forms of chemical communication is the inspiration to look at potential robotic applications. In previous work involving the use of physical chemical signals in robotics the case of one robot releasing or depositing a chemical for other robots (or the same robot) to detect and act upon has been addressed. This project moves a step forward to investigate a group of robots where each group member emits and detects pheromone chemicals. The example task addressed in the project is to use chemical signalling to help a collection of robots to assess group size. Bacteria provide a model for this kind of chemical communication. By monitoring chemical concentration bacteria can assess group size and hence modify their behaviour as appropriate. Although not intending to model bacterial quorum sensing in detail this behaviour provides inspiration for our demonstration of bi-directional communication. This paper provides details of the implementation of quorum sensing in a group of robots. The robots used in the project, their control algorithms and experimental results are presented. Both beneficial aspects and the pitfalls of pheromone communication in robotic systems are also discussed.

This paper studies the parameters contained in the truncated Fourier series (TFS) formulation for bipedal walking balance control. Using the TFS generated lateral motion reference, 3D bipedal walking can be directly achieved without any parameter adjustment. Furthermore, the potential of this TFS formulation for motion balance control has also been investigated. One more motion balance strategy is developed through the reinforcement learning, which adjusts the motion's reference trajectory according to the selected dynamic feedback in real time. Dynamic simulation results of the presented balance control method show that the resulting motion can be constrained periodical and long-distance 3D bipedal walking motions are achievable.

This paper presents a new approach to the management of the environmental map for mobile robots in dynamic environments. The environmental map is built of primitive features, such as lines, points, and even circles, extracted from ambiguous data captured by the robot's sonar sensor ring. The feature map must be managed because the indoor surroundings where mobile robots operate are continuously changing due to nonstationary objects, such as wastebaskets, tables, and people. The features are processed by trimming, division, or removal, depending on the dynamic circumstances. All processing refers to the occupancy probabilities of grid squares generated for the map features. The occupancy probabilities of the squares are updated using the Bayesian updating model with the sonar sensor data. Experimental results demonstrate the validity of the proposed method.

This paper deals with the design, implementation, and performance evaluation of a new type of 4-DOF parallel mechanism providing three translations and one rotation for high-speed handling and machining. This parallel mechanism is named H4. A necessary condition and system configuration of the H4 are also described. Hardware and kinematics of the H4 is addressed and the manipulability ellipsoid which is one of the widely used methods to examine the design of parallel mechanisms is addressed. The performance evaluation is carried out to demonstrate the H4 robot. The simulation and experimental results show that three different controllers, the PD, PD + velocity feed-forward, and dynamic compensation controller, dramatically improve the trajectory tracking accuracy.

In this paper, an application is presented of a cable-based parallel manipulator as measuring system for an experimental identification of human walking characteristics. Experimental results have been obtained by means of a new version of CaTraSys (Cassino Tracking System), which is a measuring system that has been designed and built at Laboratory of Robotics and Mechatronics (LARM) in Cassino, Italy. The new version of the CaTraSys system has been used to determine the trajectory of the human limb extremity during walking operation and furthermore the system is able to measure forces that are exerted by a limb. Experimental determination of articulation mobility is also presented with numerical and experimental results.

This paper discusses analytical and deterministic models for a plane curve with minimum deformation that may be utilized in planning the motion of elastic linear objects and investigating the inverse kinematics of a hyper-redundant robot. It usually requires intensive computation to determine the configuration of elastic linear objects. In addition, conventional optimization-based numerical techniques that identify the shape of elastic linear objects in equilibrium involve non-deterministic aspects. Several analytical models that produce the configuration of elastic linear objects in an efficient and deterministic manner are presented in this paper. To develop the analytical expressions for elastic linear objects, we consider a cantilever beam where the deflections are determined according to the Euler–Bernoulli beam theory. The deflections of the cantilever beam are determined for prescribed constraints imposed on the deflections at the free end to replicate various elastic linear objects. Deflections of a cantilever beam with roller supports are explored to replicate elastic linear objects in contact with rigid objects. We verify the analytical models by comparing them with exact beam deflections. The analytical model is precisely accurate for beams with small deflections as it is developed on the basis of the Euler–Bernoulli beam theory. Although it is applied to beams undergoing large deflections, it is still reasonably accurate and at least as precise as the conventional pseudo-rigid-body model. The computational demand involved in using the analytical models is negligible. Therefore, efficient motion planning for elastic linear objects can be realized when the proposed analytical models are combined with conventional motion planning algorithms. We also demonstrate that the analytical model solves the inverse kinematics problem in an efficient and robust manner through numerical simulations.

In this paper, a control design methodology for a new class of modular robots, so-called “uni-drive modular robots” is introduced. Uni-drive modular robots have a substantial advantage over regular modular robots in terms of the mass of each module since then employ only a single drive for powering all the joints. The drive is mounted at the robot base and all joints tap power from this single drive using clutches. By controlling the engagement time of the clutches, the position and velocity of the joints are regulated. After reviewing the structure of the uni-drive modular robot, a self-expansion formula to generate the dynamics of the robot is introduced. The control of uni-drive n-module robots is realized by blending independent joint control and theory of variable structure systems via a pulse width modulation technique. A uni-drive modular robot is used to conduct simulations and validate the control design technique.