Cross-Coupled Biaxial Computer Control for Manufacturing Systems

Biaxial control systems for generating predetermined paths under load disturbances, such as encountered in NC and CNC systems for machine tools, are conventionally designed such that the control of each axis is independent of the other. The present paper is concerned with providing cross-couplings for biaxial control systems, whereby an error in either axis affects the control loops of both axes. An algorithm for a cross-coupled control system is presented, and the performance of the cross-coupled system is mathematically analyzed and compared with the conventional CNC system having individual axis control. It is shown that cross-coupling between axes improves the contour accuracy while the velocity response of each axis is only slightly reduced. Although the proposed cross-coupled system requires additional hardware for implementation with an NC system, operation with a CNC-based system requires only software modifications to the system control program.