Force Characterization and Commutation of Planar Linear Motors

Abstract

This work examines force modeling and software-based commutation for closed-loop control of planar linear motors, motivated by the need for a robust and versatile planar robot for precision assembly. The approach taken is to make measurements of the static and dynamic force capabilities of the motor as directly as possible, and determine the applicability of simple models commonly used. Measurements of force ripple, linearity with current, force reduction with skew angle, and eddy current damping forces are presented. The high-frequency current changes required for high-speed motion are shown to make the system sensitive to both the latency and update rate of the commutator and to limit the force generation capabilities at high velocities. Although this effect is caused by multiple sources, it is shown that it is well modeled as a scalar with units of time.