Digital Disturbance Observer Design With Comparison of Different Discretization Methods for Permanent Magnet Motor Drives

Control techniques for Permanent Magnet Synchronous Motor (PMSM) drives rely significantly on digital systems, and control system discretization is essential for stability and robustness. While continuous-time analyses are widely employed for stability analysis, generally, they fall short of describing phenomena such as the waterbed effect and understanding system dynamics, especially in servo-drive applications. Consequently, discrete-time systems play a crucial role. The use of discrete-time analysis in digital motion systems of control allows for a more accurate study of system stability while addressing the abovementioned difficulties. Despite the vital role of discrete-time analysis in maximizing stability, robustness, and performance in digital PMSM implementations, there is a significant research gap in the complete analysis and investigation of discrete-time control systems. This research focuses on improving digital disturbance observer (DOB)-based speed control via discrete-time analysis by investigating various discretization techniques. Analyzing widespread discrete-time approaches that rely on analog-to-digital time conversion demonstrates that some strategies outperform others. The paper indicates that constructing a digital DOB-based control utilizing the implicit Adams approach and applying it to PMSMs enhances performance by increasing control accuracy and significantly reducing undershoot when compared to popular discrete-time methods such as Euler's, Tustin, Al-Alaoui, and others. The experimental results show that this chosen discrete-time approach has a significant impact on the efficiency of the PMSM control system. The outcomes of this research highlight the critical relevance of selecting an appropriate discrete-time conversion in improving the performance of a digital DOB motion control system with an application to PMSM drives.