Bilateral teleoperation using unknown input observers for force estimation

Teleoperation systems that are distributed over large physical distances where time delays become non-negligible are becoming popular in areas such as remote medicine and operating in hazardous environments. This work proposes a new approach to the bilateral control problem that extends an earlier approach [1] based on a sliding mode controller. The existing approach requires full state and force measurements at both the master and slave sides. Here, we propose the use of unknown input sliding mode observers to estimate the states and forces and use the estimates in the controllers. This significantly reduces the difficulty of implementation and the cost of such a system, as one need only measure positions in the system. The velocity and force signals are then estimated. A proof of stability for this new approach is given. As well, the approach is verified through a numerical simulation study as a precursor to ongoing experimental verification.