Precision profile measurement of disc surface by error motion compensation

In this study, a precision measurement method to obtain the surface profile of a rotating disc is proposed. To improve the accuracy of the estimated profile, the 3-DOF error motion included in the measured surface profile signal is simultaneously estimated and compensated. The profile of the disc is measured using a surface measuring unit equipped with one displacement sensor, and the error motion of the rotating component is measured using an error motion measuring unit equipped with a four-probe system. The developed error motion measuring unit uses a four-probe error separation technique, and the effect of zero setting errors between the probes on the compensated surface profile is analyzed. Subsequently, a process to remove the effect is proposed. To confirm the performance of the proposed method, numerical verification tests and experiments are performed using test equipment. The numerical verification tests show that the developed measuring system affords accurate shape estimation and is not affected by zero setting errors between probes. The experimental results of surface profile measurement using the proposed measurement method and the conventional one probe method are compared. The standard deviation of the measuring results using the proposed method was smaller than that of the conventional method by less than two-thirds. From this, it can be concluded that the error motions have been effectively compensated.