High-Precision Control of Machine Tool Rotary Axis Using Feedforward Compensator for Nonlinear Friction and Model Error Compensator

This paper presents the design of a position control system for the rotary axis of five-axis machine tools by roller gear cam, with a focus on robustness against frictional fluctuations to enable high-speed and high-precision motion. A prototype rotary table drive system is first modeled precisely using a mathematical model that incorporates nonlinear friction characteristics. Next, the proposed control system is designed by combining a feedforward nonlinear friction compensator and the model error compensator to mitigate modeling error based on the aforementioned model. The proposed control system is applied to a prototype rotary table drive system that simulates the rotary axis of a five-axis machine tool. Experimental results demonstrably show that the position error can be robustly reduced at the reversal point of a sinusoidal position command, even in the presence of modeling errors.