Contouring control for three-axis machine tools based on nonlinear friction compensation for lead screws

• A nonlinear friction model which concerned the eccentric friction is proposed for lead screws system.
• The effect of proposed friction model in contouring control is experimentally verified.
• Application in improving machine precise with low cost by using proposed friction model.

Friction is the main disturbance in mechanical systems especially in computerized numerical control machine tools with high precision, speed, and performance requirements. Much recent research have proven that a controller with friction compensation provides better performance. Some classical friction models such as the Coulomb–viscous–Stribeck friction model, the Lugre model, and the Generalized Maxwell Slip (GMS) model have been proposed to compensate for frictional effects to reduce the contour error and to improve the surface quality. However, most of the conventional friction models focus on frictional properties in pre-sliding regime and low velocity sliding regime. These models do not fully describe and compensate for friction in machine tool systems in case of high speed motion or insufficient lubrication. This paper presents a new friction model that combines the conventional Coulomb-viscous friction model and a nonlinear sinusoidal component for fully describing the friction behaviour of feed drive systems. In addition, this study presents controller design with feed forward compensation based on the proposed friction model. Experiments were conducted to compare the control performance between the proposed and the conventional friction models. Experimental results indicate that the mean contour error has been significantly reduced by 26% after applying the proposed controller.