CONTINUOUS MOTION NOMINAL CHARACTERISTIC TRAJECTORY FOLLOWING CONTROL FOR POSITION CONTROL OF AN AC DRIVEN X-Y BALL SCREW MECHANISM

Abstract

AC servo mechanisms are widely used in industrial application due to its advantages in higher efficiency, less maintenance, and smoother operation than DC servo mechanism. However, AC servomechanism frequently suffers from its inherently non-linear characteristics and more difficult to be controlled in positioning applications. A general step input easily drove the mechanism and stop smoothly in the open-loop environment, however, it is not the same for AC driven ball screw mechanism. Hence, the contributions in this paper are: (1) the realization of the practical control method - continuous motion nominal characteristic trajectory following (CM NCTF) control to an AC driven ball screw mechanism, (2) the design of a suitable input signal that produces sufficient rapid and smooth response during deceleration motion in the open-loop experiment. The open-loop responses used to construct nominal characteristic trajectory (NCT) are important because it significantly affects the reference following characteristic of the control system. The experimental evaluations were carried out for CM NCTF control system and PI-D control system. The results show that the designed input signal has successfully produced rapid and smooth open-loop responses during deceleration that benefit the reference position near NCT origin. Besides that, the CM NCTF control system that designed with the newly constructed NCT has demonstrated better positioning results than the PID controller with almost 10 times of motion error reduction for Y-axis for both amplitudes of 5 mm and 10 mm respectively.

Keywords

• AC-driven ball screw
• CM-NCTF
• Positioning performance
• Sensitivity
• Practical control
• Robustness