Current Closed Loop Control for Increasing Virtual Stiffness in Haptic Interaction

Virtual stiffness is a critical performance measure for haptic devices. This paper proposes a new controller to increase the virtual stiffness. The design of the controller is based on theoretical analysis of the system stability condition, which indicates that by adding a current closed loop the stability can be increased. We implemented the current closed loop controller with a first order filter and a PID control law. With properly selected parameters of the filter and the PID controller, it is possible to increase the maximum achievable virtual stiffness. Experimental results demonstrate the effectiveness of the proposed method.