Multirate control of haptic interface for stability and high fidelity

This paper presents an analytic design of multirate controllers to guarantee stable haptic interaction and high fidelity. When the reflective force is computed by using slowly simulated virtual model, the control frequency of the conventional controller becomes low. This increases the zero-order-hold effect, and makes the system unstable. We propose a multirate control method to reduce the zero-order-hold effect. The multirate controller is implemented by adding a high frequency controller to the conventional controller. The high-frequency controller is designed to compensate the energy generated by the conventional controller. The stability analysis of the multirate haptic control system shows that the stiffness of the virtual model can be increased while maintaining the stability. A nonlinear virtual coupling is designed using this multirate control scheme. The multirate controller is evaluated by mathematical analysis and experiments.