Haptic Feedback and the Internal Model Principle

Abstract

According to the internal model principle from control engineering, error feedback together with a controller containing an internal model that generates an expected disturbance signal can achieve perfect delay-tolerant disturbance rejection using only modest loop gains. While internal models of plant dynamics have been central to the study of human motor control, internal models of reference or disturbance signal generators have received very little attention. In this paper we show how the internal model principle suggests a certain control strategy for achieving steady oscillatory motion in a virtual spring-mass. The strategy relies on haptic feedback in its dual roles of carrying power and information and this dual reliance may be used to derive numerous testable hypotheses. We present results from an initial study involving N=5 human subjects in which high time-correlation between surface electromyography and commanded torque signals suggests the adoption of a control strategy based on the internal model principle.