Design and applications of the synchronized motion controller for tapping processes

In this paper, linear and nonlinear control design techniques including: (1) cross-couple control, (2) nonlinear friction compensation, and (3) disturbance observer are suitably integrated to improve control performance in synchronization. The developed controller has been applied to a two-axis motion system with an induction motor and a servo motor, in which they have very different dynamic characteristics. Experimental results indicate that the maximum synchronized error is significantly reduced from 132.1 um to 4.3 um. Moreover, the positional type cross-coupled controller has been realized on a commercial CNC tapping machine to improve the maximum synchronized error. Results of the tapping process have led to synchronization accuracy under 10 um when the spindle speed increases to the CNC maximum speed 6000 rpm to maintain satisfactory tapping processes.