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This paper introduces a novel underactuated anthropomorphic gripper for prosthetic applications. In order to extend the grasping capabilities of underactuated prosthetic grippers and improve the force transmission ratio, a mechanical lever is mounted inside the palm that allows a proper distribution of the forces and provides mechanical advantage. A static model is developed and the possibilities offered by the lever transmission are investigated. Also, a compact mechanism is introduced to synchronize the motion of the four fingers. Additionally, a mechanical selector is designed that functions as a means of mechanically programming the motion of the fingers by selectively blocking their closing motion. Finally, a prototype, including all the above features, is described and experimental validation is briefly reported.

This article discusses the development of statically balanced spatial parallel platform mechanisms. A mechanism is statically balanced if its potential energy is constant for all possible configurations. This property is very important for robotic manipulators with large payloads, since it means that the mechanism is statically stable for any configuration, i.e., zero actuator torques are required whenever the manipulator is at rest. Furthermore, only inertial forces and moments have to be sustained while the manipulator is moving. The application that motivates this research is the use of parallel platform manipulators as motion bases in commercial flight simulators, where the weight of the cockpit results in a large static load. We first present a class of spatial parallel platform mechanisms that is suitable for static balancing. The class of mechanisms considered is a generalization of the manipulator described by Streit (1991, “Spatial Manipulator and Six Degree of Freedom Platform Spring Equilibrator Theory,” in Second National Conference on Applied Mechanisms and Robotics, VIII.B, pp. 1-1–1-6). Then sufficient conditions on the kinematic parameters that guarantee static balancing are derived for this class. Finally a particular mechanism is studied in more detail to show the practicability of its design. [S1050-0472(00)01401-X]