A bottoming detector for detecting the movement of a pump shaft beyond a pre-determined distance within a cylinder is disclosed. The pump has a housing defining an elongate cavity filled with fluid, a resilient sheet with an aperture in alignment with the cavity which divides the cavity into first and second compartments, and an elongate shaft disposed within the first compartment of the cavity such that it may be moved into and out of the aperture in the sheet to cause pressure fluctuations in the second compartment. There is also a chamber in fluid communication with the second compartment. In the chamber there is actuating means responsive to excessive pressure in the chamber, that actuates a switch to indicate that the shaft has reached a certain distance into the second compartment.

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This paper focuses on the problem of force-feedback for the human-operator hand when manipulating virtual objects. We propose a method for the computation of feedback-forces that have to be applied on each individual phalanx and jinger of the human hand in order to display pertinent, kinesthetic information about static or dynamic chamcteristics of objects present in the virtual scene. External forces and moments of the manipulated virtual objects have to be mapped on the contact-forces space of the virtual grasp. The method is based on the solution of a nonlinear programming problem, formu-lated by performing a static analysis of a general, multiple contact points virtual grasp. A methodology for modelling interactions within a virtual environment, and performing realistic grasping and manipu-lation, is also presented.

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The Powered Gait Orthosis (PGO) is a powered exoskeleton developed as an experimental device to provide bipedal locomotion to individuals with physical impairment. The current prototype consists of a single degree of freedom (DOF) system for each leg, providing power and proper displacement required for bipedal locomotion . It is the goal of this research to obtain the forces that are present in the device while it is in normal operation . In addition, the time ratio of the hip function generator has been varied to determine the effect that different time ratios have on system forces and required user energy. The time ratio is the relationship between the time period that the thigh is in swing phase and when it is in support phase. Knowing the forces in the system and the optimal time ratio will allow for the design and construction of a feasible device for the rehabilitation and assistance of individuals who have lost the ability to walk.

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This paper describes the development of a system for dexterous telemanipu-lation and presents the results of tests involving simple manipulation tasks. The user wears an instrumen-ted glove augmented with an arm-grounded haptic feedback apparatus. A linkage attached to the user’s wrist measures gross motions of the arm. The movements of the user are transferred to a two fingered dexterous robot hand mounted on the end of a 4-DOF industrial robot arm. Forces measured at the robot fingers can be transmitted back to the user via the haptic feedback apparatus. The results obtained in blockstacking and object-rolling experiments indicate that the addition of force feedback to the user did not improve the speed of task execution. In fact, in some cases the presence of incomplete force information is detrimen-tal to performance speed compared to no force information. There are indications that the presence of force feedback did aid in task learning.

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A robotic grasping manipulator includes a support base, a pair of fingers disposed on the base which extend forwardly a certain distance therefrom, and a two-degree of freedom elongate thumb. The thumb is pivotally attached at a proximal end to the base to extend generally forwardly therefrom, and terminates in a distal end tip which may be moved vertically and laterally with respect to the fingers to thereby enable holding objects between one or both fingers and the thumb. The fingers are moveable in a plane toward or away from each other, and include tip sections which are pivotable downwardly in a direction generally normal to the plane of movement of the fingers. A unique linkage apparatus intercouples the fingers with the base such that a non-pivotal, back-and-forth-moving piston rod can be used to move the fingers. The fingers contain gripping structure including rigid, pointed protuberances interleaved with flexible, blunt protuberances which are longer than the rigid protuberances. With the two-degree of freedom movement of the thumb and the movement of the fingers and their tip sections, a variety of different shaped objects may be grasped and held between the two fingers and thumb.

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