Bilateral telemanipulator system with communication time delay based on force-sum-driven virtual internal models

This paper proposes a new control system for bilateral telemanipulators to overcome one of the severest problems, the instability in the presence of time delay in data transmission. The control system proposed is based on the impedance control with virtual internal models (VIMs) driven by the sum of two forces detected on a master and a slave. The sufficient condition for the stability with arbitrary time delay is given based on small gain theorem. The sufficient condition can be satisfied by choosing appropriate parameters of the VIMs. Consequently, the control system is stable under any time delay. The proposed control system is applied to an experimental teleoperation system, which consists of two manipulators different in size. Data for teleoperation are transmitted through wireless LAN (256 kbps, max.). With this system, a stable contact task (to teach a desired position of the slave) was accomplished even with the time delay of 0.5 second. And it has been experimentally verified that the system is stable when time delay varies at random or when data transmission ceases and resumes.