Robust bilateral control with Internet communication

Smith predictor is a well-known method for compensating time delay in control systems. Therefore, it has been applied to many systems with time delay so far. However, delay time should be estimated precisely in this method. So, if time delay is fluctuant and unpredictable, like the communication delay over the Internet, performance of Smith predictor deteriorates. This paper proposes "Communication Disturbance Observer". It regards the error caused by time delay as disturbance torque (or acceleration), then it can observe and compensate the error. Furthermore, it doesn´t need to estimate the value of delay time; therefore it can be applied to control systems with fluctuant and unpredictable time delay. It can be said that control system with "Communication Disturbance Observer" is robust to time delay and fluctuation of that. Effectiveness and robustness of proposed method is shown by result of simulation and experiment. In experiment, master-slave manipulator was used over the Internet. We were able to get the sense of touch from the environment of remote site.