Design of a four degree-of-freedom force-reflecting manipulandum with a specified force/torque workspace

Abstract

It is noted that the performance of force-reflecting hand controllers, also called manual interfaces or manipulanda, is at present limited more by mechanical design than by computing hardware. Some of the important mechanical features of a high-performance manual interface are low inertia, low friction, high stiffness, backdriveability, high output force capability, multiple degrees-of-freedom, and sizable range of motion. A four-degree-of-freedom manipulandum that utilizes a three-degree-of-freedom parallel-link mechanism was designed to incorporate these features. The kinematic design of the manipulator prompted the definition of a force/torque workspace as the volume of operation within which certain maximum desired endpoint forces and torques can be achieved, given actuators of limited output. The design requires low actuator torques, is small in size, and does not approach joint limits in the workspace.