Speed estimation comparison between full order state observer & Kalman filter for a haptic interface

A haptic system is an articulated mechanical structure with motors, sensors as well embedded electronics allowing force feedback. It enables the user to interact with virtual reality through the sense of touch and sight. Speed control of such systems usually becomes unstable at low speed range due to the imposed speed by the operator's hand. This paper describes the implementation of a full order state speed observer as well as a Kalman filter for a single degree of freedom haptic interface driven by a permanent magnet synchronous motor. Those two methods allow accurate speed estimation. The observer and the filter design procedure for haptic interface are analyzed in this paper. In addition, their influence on system stiffness is illustrated, taking into consideration variations of the system inertia.