This paper describes the development of a novel compact magneto-rheological (MR) fluid brake with high transmitted torque and a simple structure. The MR fluid brake has two shearing disks with an electromagnetic coil located between them. Such a structure enables the brake to have a small radial dimension and a large torque transmission capacity. In the design process, a Bingham viscoplastic model is used to predict the transmitted torque. Electromagnetic finite element analysis (FEA) is performed to assist the magnetic circuit design and structural parameters' optimization. The novel brake design is prototyped and studied. Experimental results show that a compact MR fluid brake with high transmitted torque is successfully achieved.

This research presents a new and generic geometric approach that characterizes the kinematic singularity of wheeled mobile robots. First, the kinematic models of all the common wheels are obtained: fixed, centered orientable, castor, and Swedish. Then, a procedure for generating robot kinematic models is presented based on the set of wheel equations and the null space concept. Next, two examples are developed to illustrate the nongeneric singularity characterization. In order to improve that approach, a generic and practical geometric approach is established to characterize the singularity of any kinematic model of a wheeled mobile robot (WMR). Finally, the singular configurations for many types of mobile robots are depicted employing the proposed approach.

The purpose of this paper is to present a robust tracking control algorithm for underactuated biped robots capable of self-balancing in the presence of external disturbances. The biped is modeled as a five-link planar robot with four actuators located at hip and knee joints. A sliding mode control law has been developed for the biped to follow a human-like gait trajectory while keeping the torso nearly upright. The control forces are calculated by defining four first-order sliding surfaces as a linear combination of the torso and the four joint tracking errors. The control approach is shown to guarantee that all trajectories will reach and stay on these surfaces during each step, while the walking cycle stability is maintained through a Lyapunov function. The criteria for asymptotic stability of the surfaces are presented and a numerical search method is implemented for the selection of the corresponding surface parameters. The paper further investigates the robustness of the controller in response to disturbances. Numerical simulations demonstrate the tracking stability of the biped's multistep walk and its human-like response to an external disturbance.

This paper presents a modular control architecture that enables a mobile manipulator to be compliant and perform manipulation tasks in partially known everyday human environments. An impedance velocity/force controller that allows the execution of a great variety of tasks under the Task Frame Formalism (TFF) is implemented.

Tasks are represented as a net of basic abilities which are performed by the robot using the impedance controller. Mechanisms for switching between abilities according to the robot's perceptual state are defined.

We show the validity of our approach on the UJI Service Robot, making it to perform a common daily task such as opening a door. Finally, we apply this framework to make progress on the new version of the UJI Librarian Robot, making a great step forward in the way the robot manipulates books.

Evidence is presented to indicate that the answer is, “Yes, sometimes.”

Spinning up a Power®ball—a hand-held gyroscopic toy or exerciser that exhibits rotor spin-up when applying appropriate torque to its casing—is a fairly easy task for a human but rather complex to perform with a robot. To accomplish the task of spinning up the rotor of the Power®ball with a robot, we measured the motion of a human and identified the conditions an individual uses for a successful spin-up. Several control approaches were applied to the device mainly using feedback information from the velocity counter and force/torque sensor to synchronize the torque exerted by the device and the motion of the robot. Best human imitation was achieved with two modified learning methods with highest rotor speeds in excess of 1480 rad/s, rating among top 100 world Power®ball players.

This study develops a novel image-guided robotic system that can be used to position biopsy needles or drill fixation holes. After the patient has received a CT-scan, the registration of the image, localizer (patient), and robot frames will be done by finding the optimum transformation matrix among the image and localizer coordinates of the fiducial markers and the DRFs mounted on the robot. Then, surgical paths planned on the computer displayed images can be transformed to the robot frame, and the robot is thus capable to move surgical tools to the preplanned location. The positioning error is about 2 mm and the orientation error is about 0.23°.