Correction of positioning and angular errors for ball screw feed unit

Abstract

In the present study, we developed a new feed correction mechanism which corrected not only a positioning error (i.e., feed deviation) but also an angular error (i.e., yaw of a table). A correction mechanism including two piezoelectric actuators was constructed and installed between double nuts. The correction mechanism corrects positioning error if both piezoelectric actuators are expanded to the same length, and corrects angular error if one piezoelectric actuator is expanded and the other is contracted. First, the positioning and angular errors correction functions were investigated separately. A load was applied to one side of the table in order to simulate a counter force during machining. In the positioning error correction, a low-frequency component of positioning error was corrected effectively under the condition that the load for the table was set to at least 50 N. In the angular error correction, the correction capability was comparable to that of the positioning error correction up to the maximum load torque to the table, 1.4 Nm. The load torque was limited to 1.4 Nm because both piezoelectric actuators reached their saturation voltage. Finally, simultaneous correction of positioning error and angular error was examined, and the simultaneous correction capability was confirmed to be equivalent to the separate correction capabilities.