Time-delay control with adaptive gain dynamics for robot manipulators

Adaptive gain dynamics for time-delay control (TDC) of robot manipulators is proposed. TDC is a well-known controller for robot manipulators: it is model-free, efficient, and robust. The gain of conventional TDC is a constant matrix, which could pose two drawbacks. First, because the gain is tuned manually by a trial-and-error method, one cannot be convinced whether the gain is well-tuned. Second, when the system dynamics varies rapidly, and the posture of the robot manipulator has changed significantly, the performance of the conventional TDC degrades with a constant gain. To cope with these problems, we propose an adaptive gain dynamics for the TDC by using sliding variables and acceptance layer concept. The time-varying acceptance layer automatically adjusts the gain to minimize the sliding mode error. As a result, the TDC with the proposed adaptive gain dynamics becomes adaptive and robust. The effectiveness of the proposed gain dynamics has been verified experimentally using a whole arm manipulator.