A novel observer design for friction estimation

In this paper, we propose a novel adaptive friction estimator for simple mechanical systems with Coulombfriction. We assume that the friction constant is unknown and we propose an adaptive observer for itsestimation. We show that under certain conditions the observer structure is asymptotically stable. The pro-posed observer dynamics has two tuning parameters and essentially behaves as a second-order switchingsystem. These parameters could be utilised to tune some time domain performance measures such assettling time, per cent overshoot. etc., under certain conditions. Lastly, simulations reveal that when theactual friction is not confined to Coulomb friction only, the proposed design improves the position trackingperformance, especially when the position controller has low bandwidth.