Integrating PWM amplifier with the design of mechatronic systems for energy-efficient precision motion

Abstract

This paper proposes an integrated mechatronic system design to realize insensitivity to the current ripple of a switching current amplifier that drives electromagnetic actuators in high-precision motion systems. Switching current amplifiers are desirable for high energy efficiency with a concern that the resulting current ripple impairs the achievable positioning resolution. To eliminate this concern, a motion system is developed based on a flexure-guided voice coil actuator, which is driven by a switching current amplifier. A resonator is mounted onto the mover, creating an antiresonance at 11.3kHz. This antiresonance is used to absorb the mover vibrations stemming from the current ripple. For this purpose, pulse width modulation (PWM) is used in the current amplifier such that the switching frequency is accurately tuned to the antiresonant frequency. Experiments reveal that the developed switching current amplifier reduces the power loss by a factor of 5.6 in comparison with a linear current amplifier. However, the switching current amplifier creates a current ripple of 0.77A and oscillates the mover, resulting in a parasitic vibration of 5.1nm. The use of the antiresonance successfully eliminates this vibration, decreasing the positioning error by a factor of three to 1.6nm.