A Multirate approach to haptic interaction with deformable objects single and multipoint contacts

In this paper we describe a new solution for stable haptic interaction with deformable object simulations featuring low servo rates and computational delays. The solution presented is a combination of the local model and the virtual coupling concepts proposed in the past. By varying the local model impedance depending on the local stiffness of the deformable object, the interaction between local model and simulation can always be made stable independently of low servo rates or computational delays. Moreover, by using more complex local impedances that feature an integral term, we are able to control the steady-state error between the device and the surface of the deformable object. This allows us to maximize the Z-width of the simulation, while obtaining overall stable behavior without using any added damping. The local model is always computed using the current deformable object surface, thus allowing for multipoint contact interaction, i.e., allowing multiple users to feel each other's influence on the object. The proposed solution is presented and analyzed in a multirate setting. Experimental results employing a Phantom haptic interface are presented.