Power grasp is redefined as a type of grasp that its mechanism can resist passively against external forces without relying on feedback control of join2 torques. A computational algorithm is invented to calculate the critical extemal force, a force which is requisite to move the grasped object in a definite direction. Virtual work is proposed as the quality measure of the robustness of power grasp. Because this measure i s a scalar, it is convenient and suitable for the planning of power grasp. The effectiveness of the computational algorithm of critical external force and quality measure of robustness of power grasp is verified with a numerical eza mple.

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In this paper, we propose a control scheme of parallel manipulators focusing on the accuracy of acceleration on the end plate, an important factor when parallel manipulators are used as acceleration displays such as a driving simulator. In order to achieve a smooth and accurate acceleration on the end plate, we combine two controllers: A dynamic controller to achieve accuracy of the position and to stabilize the system, and an H∞ controller to feedback the acceleration of the end plate to cope with the unmodeled dynamics such as mechanical flexibility and friction. The main problem of dynamic control is computational complexity. We applied parallel processing to reduce the latency and realized real-time dynamic control. The designed H∞ controller is added outside the closed loop of dynamic control to remove the vibration of the structure and the influence of unmodeled dynamics.