Time-Varying Delayed Bilateral Teleoperation Without Force/Velocity Measurements

A bilateral teleoperation control scheme is proposed for the case of time-varying delays in the communication channel. The proposed scheme relies only on joint position measurements to estimate both velocities and external forces by using an extended-state high-gain observer. The estimated signals are in turn employed in a decentralized controller in a master-slave configuration. The control design is based on: 1) local force compensation, which improves the system stability; 2) direct force reflection, which increases the telepresence; and 3) only local damping injection, to deal with the instability problems arising from the time-varying delays in the communication while employing a simple three-channel architecture. A formal mathematical analysis is developed to guarantee the ultimate boundedness of estimation and tracking errors to an arbitrarily small region around zero. To test the validity of the proposed approach, experimental results are presented, including a comparison with an approach reported in the literature and a real-case communication over a long distance through the Internet.