On the finite time force estimation for bilateral teleoperation of robot manipulators with time varying delays

One of the biggest challenges in the bilateral teleoperation of robot manipulators is to get transparency and telepresence between the local (master) and the remote (slave) manipulator. For these goals, it is advisable to transfer contact force measurements from one side to the other through the communication channel. However, there may be some reasons for which it is not necessarily desirable to employ force sensors. For instance, they are expensive, sensitive to noise, and they can be too big to be used in some small devices. Therefore, some estimation approaches may be advisable. This contribution shows the design of a position/force control scheme for bilateral teleoperators with time varying delays based on the estimation of velocities and forces by using only joint position measurements. Under some relaxed assumptions it is shown that position and force tracking errors become ultimately bounded with arbitrarily small ultimate bound in finite time. To the best of the authors' knowledge there are no control schemes for bilateral systems with all the previous characteristics since the available ones assume constant time delays. The new proposal is tested by means of simulations and experiments showing a good performance both in free and constrained motion.