ADAPTIVE FRICTION COMPENSATION WITH PARTIALLY KNOWN DYNAMIC FRICTION MODEL

This paper illustrates the application of a model-based adaptive frict ion compensation on a DC motor servomechanism. The dynamic friction mo del and the control structure studied previously by the authors were u sed as a basis for this study. The paper first proposes a two-step off -line method to estimate the nominal static and dynamic parameters ass ociated with the model. Then two adaptive globally stable mechanisms a re introduced to deal with structured normal forces and temperature va riations. Assuming that a nominal friction model is known and that the friction variations can be suitably structured, adaptation is perform ed on the basis of only one parameter. The paper presents experimental results validating the identification of the dynamic friction model a nd the adaptive control scheme. These results show that the adaptive l oop improves over a fixed compensation scheme and over a PID controlle r without friction compensation.