Wide-bandwidth bilateral control using two stage actuator systems: Evaluation results of a prototype

This paper proposes a two stage actuator system that consists of a coarse actuator driven by a ball screw with an AC motor (the first stage) and a fine actuator driven by a voice coil motor (the second stage). The proposed actuators are applied to make a wide-bandwidth bilateral control system. The first stage has a wide moving range with a narrow control bandwidth, and the second stage has a narrow moving range with a wide control bandwidth. In the proposed method, by consolidate these two inexpensive actuators based on a control design to separate bandwidth, a wide bandwidth bilateral control system can be constructed. Simulation results show that a higher transparency, i.e., better force and position responses between a master and slave, is achieved by using the proposed system compared with a narrow-bandwidth case using a single ball screw system. Furthermore, a prototype of the two stage actuator has been developed and basic performance was evaluated by experiment. Experimental results showed that a light mechanical impedance with a mass of 10 g and damping of 1.6 N/(m/s) that is an important factor to establish good haptic devices was successfully implemented.