Bilateral energy transfer in delayed teleoperation on the time domain

The time domain passivity framework is attracting interest as a method for granting stability in both telerobotics and haptic contexts; this paper employs this approach in order to introduce a novel concept, the Bilateral Energy Transfer for haptic telepresence. Loosely speaking, the Bilateral Energy Transfer is the straightforward transfer of energy between the two opposite sides of a teleoperation network, the master and slave robots. In an ideal telepresence scenario master and slave robots behave as rigid connected masses [1], and their power exchange is lossless; conversely, realistic scenarios include sources of energy leaks, i.e. elements that modify the power flows in the network. Moreover, if energy leaks have an active nature, they become source of instability for the system. This work isolates two sources of instability normally present in a teleoperation system, i.e. the delayed communication channel and robot velocity estimation based on digital position acquisition. These energy leaks are counterbalanced by two independent controllers, whose design is based on energetic consideration, and whose employment allows to achieve the Bilateral Energy Transfer. The presented arguments are sustained by simulations and experiments.