Friction compensation using time variant disturbance observer based on the LuGre model

This paper reports experimental evaluation results of a time variant disturbance observer based on the LuGre friction model for friction compensation. The observer is designed from state space expressions of a controlled plant with the LuGre model that is locally-linearized every sampling period. Thus, observer gains derived from the linearized model become time variant ones as a function of velocity. Parameters of the LuGre model were experimentally identified for a linear stage driven by a ball screw with an AC motor, i.e., a controlled plant. To show the validity of the proposed method, experiments using the controlled plant were conducted to evaluate tracking errors for positioning control with and without the proposed disturbance observer. From the experimental results, it has been confirmed that the proposed disturbance observer can eliminate influence of the friction and is effective to improve positioning accuracy.