Contouirmg control of biaxial feed drive systems with non-linear friction compensation

Contouring control that employs tracking error components normal to desired contour curves as feedback signals is an effective method of improving contouring accuracy in machine tool control. In this paper, a contouring control method for biaxial feed drive systems is presented, which transforms tracking errors in each feed drive axis into errors that are reference to a moving frame around the desired position. The method is extended to include a referenced adjustment function for reducing inherent contour errors in the moving frame approach. Because friction is a major disturbance in motion control of feed drive systems, a friction compensation method for the contouring control systems is proposed. Since properties of friction cannot be predicted accurately, an estimation method of the friction model parameters is developed, and a robust controller for the estimation errors is designed. The effectiveness of the proposed method is demonstrated by experimental results with circular contour curves.