Cross Coupling Controller for Accurate Motion Synchronization of Dual Servo Systems

In order to attain higher manufacturing efficiency, “dual” (two) servo systems are widely used in advanced Computer Numerical Controlled (CNC) machine tools. A well-known example is the linear motor driven gantry type of micro machine tools where dual servos are employed to drive the heavier gantry axis. Recently, dual servos are also used in spindle systems. “Double sided milling” is an example where two spindles are required to cooperatively remove material on both sides of a workpiece. Synchronization of dual servo systems is crucial for achieving the desired manufacturing accuracy. This paper presents a crosscoupling controller to accurately synchronize dualmotor driven servo systems. Proposed cross coupling controller penalizes differential positioning error between dual servo drives by modifying the reference position and velocity commands. It improves motion synchronization without affecting the overall tracking bandwidth. A tuning method for the proposed controller is also presented for the control engineer’s practice.