Adaptive cross coupling control for CNC machines

Abstract

Currently, most multi-axis in the modern CNC machines manipulate individual axial control in each axis of motion which is separately driven and the control loop only one axis. It is known that modeling uncertainty and nonlinear disturbance significantly affect performance in the tracking control on each axis and the contour cutting in CNC machines. Control design based on the traditional approaches in each axis may be insufficient to handle that kind of task in multi-axis motion platforms. An approach is presented here to improve the CNC cutting performance in contour tracking by incorporating adaptive proportional-integral-derivative (APID) and cross-coupling control (CCC) for the purpose. We propose an improved method for precision multiple motion control by combining individual axis control and CCC in the controller design. It consists of two parts: APID and sliding mode control which is with adjustable PID control gains influenced from a sliding hyper plane to reduce tracking error of each axis.; adaptive CCC works to deal with the tracking error of the individual axis together with the coupling error and applies the combined error to a decoupling controller for contour error minimization. Extensive simulation results based on the three-axis motion is compared to traditional PID control showing the effectiveness of our proposed design.