Implementation of a force-reflecting telerobotic system with magnetically levitated master and wrist

摘要

Aspects of control and coordination of a new force-reflecting teleoperation system have been addressed in this thesis. A six-degree-of-freedom magnetically levitated fine-motion device is used as the teleoperation master. The slave system is a redundant coarse-fine manipulator system which consists of a conventional robot equipped with a magnetically levitated fine-motion wrist identical to the master. The environment and the human operator applied forces are measured by two six-axis force-torque sensors. Taking advantage of the Lorentz magnetic levitation technology, the system can eliminate mechanical problems such as friction and backlash, and is able to achieve high frequence response, precise positioning and excellent force-reflection quality. With using rate control for large motion and position control for small motion, the slave system can be controlled over a large workspace by the master without operator controlled indexing and without sacrificing position resolution. An overshoot problem due to time delay in the coarse manipulator position data has been solved by using decoupling coarse-fine control approach, in which the coarse manipulator is only responsible for rate control and the fine-motion wrist is responsible for position control. The system performance was quantified by performing general teleoperation tasks, such as free motion tracking, hard contact and exertion of forces. The teleoperation system has over 15Hz position bandwidth and several kHz force bandwidth. At present, the force bandwidth is limited by computation delays to a few hundredHz (this number will increase with a faster computing system).