Optimal control for haptic rendering: Fast energy dissipation and minimum overshoot

Controlling haptic devices in an optimal way is crucial to achieve both, best performance and most realistic haptic feedback. The present article investigates control design of a single degree of freedom haptic device that is interacting with a human operator and rendering a virtual wall affected by time delay. To this end, it suggests different optimization criteria based on the step response of the haptic system. These criteria cover fundamental requirements for efficiently using haptic devices, particularly fast settling and minimum overshoot. For each criterion an optimal path and point inside the stable region of the virtual wall parameters is derived. These optima depend mainly on the system mass, sampling time and time delay. This approach is supported by experiments on two devices, a Falcon haptic device and a DLR/KUKA Light-Weight Robot arm.