Design of a Disturbance Observer and Model-Based Friction Feedforward to Compensate Quadrant Glitches
Accurate motion control requires measures to compensate the effects of friction that contribute to positioning and contour tracking errors. The complex nonlinear behaviour of friction at motion reversal causes a unique tracking error known as quadrant glitch. Friction can only be partly compensated using linear feedback control strategies such as PID, cascade P/PI or state-feedback control. Model and non-model based friction compensation strategies are necessary to acquire sufficiently high path and tracking accuracy. This paper analyses and validates experimentally three different friction compensation strategies for a linear motor-based xy feed drive of a high-speed milling machine: (i) friction model based feedforward, (ii) an inverse-model-based disturbance observer, and (iii) the combination of friction model feedforward and disturbance observer. Two different friction models are considered: a simple static friction model and the recently developed Generalized Maxwell-slip (GMS) friction model. The combination of feedforward based on the GMS friction model and the inverse model-based disturbance observer yields the smallest radial tracking error and glitches.
KeywordsFriction Force Friction Model Disturbance Observer Stribeck Curve Friction Compensation
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