A Six-Degree-of-Freedom Magnetically Levitated Variable Compliance Fine-Motion Wrist: Design, Modeling, and Control

It has been shown that equipping conventional robots with fast high-resolution fine-motion devices leads to dramatic performance improvements. The success of such a coarse-fine approach to manipulation depends critically on the design of the fine manipulator. This paper describes a high-performance six-degree-of-freedom magnetically levitated fine-motion wrist with programmable compliance. Design considerations, a discussion of the major elements of the device, and issues of modeling, kinematics, dynamics, and control are presented. A prototype wrist has been built and controlled successfully. Experimental results, including high bandwidth position control, compliant control, and the emulation of several mechanisms through software gain setting, establish the use of magnetically levitated robot wrists as a new and desirable option for manipulation tasks requiring high precision and fine compliant motions. © 1991 IEEE