Yaser Maddahi, Ramhuzaini A. Rahman, Wai-keung Fung, and Nariman Sepehri
Network delay, packet loss, bilateral teleoperation, control architec-ture, hydraulic manipulator
In this paper, the effects of time delay and packet loss incurred incommunication channel, are examined on the performance of bilaterally controlled hydraulic actuators under various control schemes. The controllers are force reflection (FR), position error (PE), combined force reflection and position error (FP), and four channels (FC). The performance of each control scheme is evaluated by performing a set of experiments on a test rig comprising haptic device, simulated valve-controlled hydraulic actuator, and communication channel. The performances are then compared using three criteria: position tracking, force tracking, and fidelity of the perceived stiffness. The experiments are performed under time delays ranging from 100 to 1,000 ms and percentage of packet losses up to 75%. It is shown that packet loss affects the signal oscillations, while time delay increases the steady-state tracking error. The FP controller shows the best performance with the least tracking error and signal oscillation in both position and force tracking. The FC scheme is shown to be least effective due to large tracking oscillations in the presence of packet loss and/or time delay. The value of stiffness perceived by the operator is found to decline with increasing time delays or packet losses in all controllers.
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