Haptic Rendering of Virtual Hand with Force Smoothing

In this paper, we present methods to generate a stable and realistic force rendering between virtual hand and object for a hand rehabilitation system. There are multi-contact regions between hand and object. For each contact region, the virtual contact force is modeled upon the spring-mass model. As direct rendering with spring-mass model in a large stiffness will induce instability of the haptic device, we apply a force-smoothing method by limiting the maximum force variation to guarantee the stability in the haptic rendering. The system experiment results demonstrate that the proposed method can provide satisfactory stable haptic display. And the maximum virtual stiffness that the system can simulate increases from 0.7 N/mm to 1.6 N/mm by using force smoothing process.