The authors previously (1999) showed that a regular sliding-mode controller is difficult to be used in bilateral teleoperation systems with varying time delay in that its nonlinear gain should be set based on the worst time delay. As an alternative to the regular sliding-mode controller, a modified sliding-mode controller was proposed to compensate the varying time delay and to guarantee its nonlinear gain to be independent of the magnitude of the time delay. In this paper, the validity of the proposed control scheme is demonstrated by a series of experiments with a 1-DOF master/slave teleoperation system. In the experiments, it is shown that the proposed controller effectively compensates the effects of the varying time delay even when the magnitude of the delay, i.e., RTT (round-trip time) in the communication line becomes as large as 4.0 s, while the performance of the regular sliding-mode controller deteriorates, especially with a large value of the force scaling factor.
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