Proposes using two under-actuated robotic systems as two legs of a walking machine. Since the ankle joints of both legs have no actuation, the walking machine remains upright only when it is balanced via a computer-controller. The design of a stabilizing controller for one under-actuated leg, using a μ-synthesis approach, is explained in detail. The system at the equilibrium can be represented by a non-minimum phase system. The right half plane zero severely limits the achievable closed-loop bandwidth and robustness in modeling errors.

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The design of a prosthetic device for patients who have suffered loss of muscular control of the hand is described. The authors present some preliminary design considerations, with emphasis on the sensing and actuation systems. The prototype achieves several movements of the fingers of the hand. The design is closely based on the natural human hand to ensure effectiveness and comfort. The exoskeleton is worn as a tight glove, and the joints are flexed by cables and motors. Some preliminary test results are reported.

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The Rutgers Master II-ND glove is a haptic interface designed for dextrous interactions with virtual environments. The glove provides force feedback up to 16 N each to the thumb, index, middle, and ring fingertips. It uses custom pneumatic actuators arranged in a direct-drive configuration in the palm. Unlike commercial haptic gloves, the direct-drive actuators make unnecessary cables and pulleys, resulting in a more compact and lighter structure. The force-feedback structure also serves as position measuring exoskeleton, by integrating noncontact Hall-effect and infrared sensors. The glove is connected to a haptic-control interface that reads its sensors and servos its actuators. The interface has pneumatic servovalves, signal conditioning electronics, A/D/A boards, power supply and an imbedded Pentium PC. This distributed computing assures much faster control bandwidth than would otherwise be possible. Communication with the host PC is done over an RS232 line. Comparative data with the Cyber-Grasp commercial haptic glove is presented.

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This paper analyzes the general requirements of Haptic Interfaces (HIs) for Virtual Prototyping operations. In particular two different paradigms of interaction with virtual objects are presented, respectively based on an anthropomorphic and a desktop Haptic Interface. The main aspects of mechanical and control system design of HIs and force rendering in Virtual Environments are discussed too. The experimental results of the simulations conducted with a force feedback arm exoskeleton are presented, pointing out the current limits of the existing devices and outlining the future developments.

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Increasing evidence suggests that locomotor training can greatly improve human walking ability after neurological injury (Barbeau et al. 1998). After stroke or spinal cord injury, treadmill stepping with manual assistance and partial body weight support facilitates re-learning how to walk. However, manual assistance is labor intensive and highly variable from therapist to therapist. A lightweight powered lower limb orthosis that can assist locomotor training would decrease labor requirements and provide more con-sistent therapy. In addition, a powered orthosis would also provide the means to design controlled motor learning studies on human locomotion. Thus, we designed a pneumatically powered, myoelectrically controlled ankle-foot orthosis as a tool for rehabilitation and
studying human locomotor adaptation.

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