Haptic display of movable virtual object with interface device capable of continuous-time impedance display by analog circuit

Stability of haptic interface is an important issue in virtual reality because ail operator touches directly a haptic interface device. The stability is influenced by sampling period and discrete-time property of control system. In this paper, for decreasing the influence of sampling system, we propose a haptic device with an analog circuit, which is placed between the computer and the haptic device and works as springs and dampers. The control system can specify the stiffness and the damping coefficients and their equilibrium. For displaying virtual objects that can move in virtual environment, we propose two methods to utilize the device, continuous-time coupling impedance (CCI) method and continuous-time object impedance (COI) method. We also analyze the passivity of each method for 1-DOF display system. Finally, some experimental results in two-dimensional virtual environment are presented to show the validity of the proposed approach.