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Improving Perception in Time-delayed Telerobotics

Telerobotics Lab, Stanford University, Stanford, CA, USA, tanner{at}stanford.edu

Günter Niemeyer

Telerobotics Lab, Stanford University, Stanford, CA, USA

Telerobotics has long struggled to provide realistic force feedback to a user, especially across substantial time delays. Wave variable based controllers provide stable force reflection at frequencies up to a few hertz for typical communication delays; however, the bandwidth of human perception extends to a thousand hertz. In this paper we aim to improve the user’s perception by constructing a fundamentally asymmetric controller that better matches the sensory capabilities of the human operator. The improvements stem from two extensions to a normal wave variable controller. First, we revisit wave reflections and utilize wave filtering and shaping to separate distracting oscillations from useful reaction information. This avoids excess damping inherent to impedance matching and enhances the low-frequency feel of the system. Secondly, we incorporate high-frequency feedback from a force sensor located at the slave end-effector. This augmented system leverages the passivation capabilities of wave filters to compensate for energy generation. It renders the complete spectrum of environment interaction forces to the user, allowing the perception of small environment features across substantial delays. These improvements are tested and validated in three simple experiments on a three-degrees-of-freedom testbed.

Key Words: teleoperation • force feedback • force sensor • time delay • wave variables • passivity • human perception

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