Design and Analysis H-Infinity Controller for Machine Tools

Low, Jie Zuen (2024) Design and Analysis H-Infinity Controller for Machine Tools. Final Year Project (Bachelor), Tunku Abdul Rahman University of Management and Technology.

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Abstract

Milling machines such as ball screw drive and linear drive are getting more advanced and traditional controller are unable to cope with the non-linear cutting forces as well as giving low accuracy and precision.This is because of disturbance forces occur during operation such as friction force and vibration force which exhibit nonlinear behaviours. As a result, these forces affect the accuracy of the ball screw drive system and causing tracking errors which lead to low quality of products in such of poor surface roughness. To solve this problem, three type of controllers were designed for ball screw drive system mainly are PID, NPID and H-infinity controller. Three types of cutting force were collected using a NEOMOMAC dynamometer based on the milling process of a CNC machine on an aluminium workpiece with spindle speed of 4000rpm, 5000rpm and 6000rpm. The performance of designed controllers in terms of tracking error reduction and disturbance rejection. H-infinity controller is capable to reject the disturbance by an average improvement of 79%, 74% and 83% in 4000rpm, 5000rpm and 6000rpm respectively while NPID controller has an average improvement of 4% and 8% in 4000rpm and 5000rpm respectively. In addition, H-infinity and NPID had reduced the tracking error 23.15% and 21.1% compare with PID as benchmark controller. H-infinity controller outperforms PID and NPID controllers in terms of tracking error reduction and disturbance rejection. Lastly, H-infinity controller outperforms the PID and NPID controllers and shows that the output is more precise when compared to the reference input.