Wave dynamics intrinsic in symmetric four-channel bilateral teleoperation: Mutual impedance-based motion control

Bilateral teleoperation is a network control system that connects distant locations under force sensation and contributes to task execution. The motivation of this study is to focus on the importance of symmetry in bilateral teleoperation systems and to design controller configurations with symmetry. This study employs the acceleration control-based four-channel bilateral teleoperation (AC4BT). AC4BTs have the regulator to zero in resultant force and the controller in positional difference, which can precisely achieve bidirectional force transmission and position synchronization while maintaining its symmetric structure. However, the coupled design of the force regulator and position controller remains challenging. The mutual impedance-based motion control approach derives and discusses the intrinsic wave dynamics in AC4BT under communication delay. The mutual impedance determines the transmission characteristics of force and position in bilateral teleoperation since it corresponds to the characteristic impedance in distributed-parameter systems. This study proposes the force-proportional-integral (force PI) and position-proportional-derivative (position PD) controllers, with the gain settings canceling the frequency-dependent terms. Without interfering with the realization of the control objectives, this brings the phase relationship between the force and velocity in manipulation closer to that performed in a no-delay situation. Experimental results verify the proposed approach.