A PID approach to suppressing stick-slip in the positioning of transmission mechanisms

Transmission mechanisms usually play an important role in mechanical systems. This type of device is responsible for transferring energy to a remote site, and may change the type of motion, as needed. However, the inherent friction will handicap the overall system performance. This nonlinear property brings about severe stability problems, including the limit cycle, which strongly constrains the accuracy and bandwidth of any mechanical system. This paper presents a tuning strategy for PID controllers to avoid the phenomenon of stick slip caused by friction in transmission systems. In addition, to achieve sufficiently smooth motion, a cycloidal trajectory profile adopted from cam theory is also applied. Precise positioning can therefore be accomplished by employing the cycloidal profile, together with appropriate controller parameters. Encouraging control performance is demonstrated experimentally. Comparisons between the proposed approach and an adaptive control method are also shown. (C) 1998 Elsevier Science Ltd. All rights reserved.