Performance analysis of time-delay bilateral teleoperation using impedance-controlled slaves

Recently developed impedance-controlled robots are better suited than conventional industrial robots for executing human-like contact tasks. However, performance of a system when using such device as a slave in time-delay bilateral teleoperation is still unknown. It is the goal of this paper to analyse the performance of a 4-channel time-delay bilateral teleoperation system with an impedance-type master device commanding an impedance-controlled slave. Using the newly introduced reflected damping in free-air criterion, it is shown that the damping felt by the human operator interacting with the system while the slave is in free-air is dependent on the local controller parameters and increases linearly with the time-delay with a factor dependent on the master and slave proportional controller gains. The transparency analysis of the system shows that, independently of the time-delay or controller parameters, a stiffness equal to that of the environment is transmitted to the operator. The experimental validation, using a 1-dof master-slave teleoperation system, shows that the proposed criterion can approximate the identified damping with an accuracy of 5% for time-delay values up to 30 ms. It is also highlighted by the experimental results that, in the transition between free-air and rigid contact, the impedance rendered to the operator is lower than that of the actual environment.