We have designed, implemented, and tested an electromagnetically driven fast tool servo for diamond turning precision contoured surfaces with nanometer resolution. Our device is based on a novel ultrafast motor utilizing permanent magnets for flux bias in conjunction with steering coils used to control the actuator force. Experimental results demonstrate that our ultrafast tool servo has a stroke of 30 micrometers, achieves 23kHz closed-loop bandwidth, as low as 1.7nm RMS tracking error, 500G peak acceleration at 10kHz open-loop operation, and 2.1nm (0.04%) error in tracking a 3kHz sinusoid of 16mm p-v. To drive and control this ultrafast tool servo, a 1kW linear power amplifier and a high-speed real-time computer with 1MHz sampling rate have been designed and implemented.
This project is funded by National Science Foundation under Grant award number DMI-0322590.
Manufacturing free-form optical surfaces increasingly requires fast tool servos with higher bandwidth, higher acceleration, and higher accuracy. As an alternative solution to conventional piezo-based micro-positioning devices, electromagnetic actuators working on normal stress can potentially achieve much better performance than existing state of fast tool servo technology.
Design ultra-high performance fast tool servos based on novel electromagnetic actuators, high performance precision power amplifiers, and high performance real-time computers.
Our fast tool servos performance: 23kHz closed-loop bandwidth, 1.7 nm RMS positioning error, 2.1 nm RMS error for tracking 16 micron peak-to-valley sinewave at 3k Hz, 500 G acceleration up to 10 kHz.
Our linear amplifier has 100kHz band and 1 kW.
Our real-time computer has achieved 1 MHz sampling rate for a control loop including 16-bit A/D, control algorithm calculation, and 16-bit D/A.
Xiaodong Lu, David L. Trumper, "UltraFast Tool Servos for Nano-Surfaces", Proceedings of ASPE 2004 Annual Meeting, Orlando, FL.
Xiaodong Lu, David L. Trumper, "Ultrafast Tool Servos for Diamond Turning", Annals of the CIRP 2005, accepted for publication.