Control schemes for stabilization of force-reflecting teleoperators with communication delay

We present a general approach to stabilization of bilaterally controlled teleoperators in presence of delay in the communication channel. A standard teleoperation system consists of two manipulators called master and slave, and a communication channel between them. The master is moved by the human operator, and the information about master´s trajectory is sent through the communication channel to the remotely located slave. The slave is controlled to follow the motion of the master. In force-reflecting (or bilateral) teleoperator systems, a contact force due to the environment is measured on the slave side and sent back to the motors of the master. In the presence of time delay in the communication channel such a force feedback makes a telerobotic system unstable. The general idea of our approach is to make both the master and the slave manipulators input-to-state stable, so that stability of the overall telerobotic system can be guaranteed for any communication delay by using an appropriate version of the ISS small gain theorem. We discuss several versions of the stabilization algorithm proposed, in particular, an adaptive version as well as a version which does not utilize velocity measurements.