PERFORMANCE ANALYSIS OF DISCRETE-TIME DISTURBANCE OBSERVATION FOR PERMANENT MAGNET SYNCHRONOUS MOTORS

Abstract

The stability and performance analyses of control systems are of critical importance in the field of engineering. While motion controllers are typically implemented using computers or microcontrollers, continuous-time analysis methods are often utilized due to their simplicity. However, these methods may not fully capture some of the dynamic behaviors of robust digital motion controllers based on disturbance observer (DOB). To address this, the Bode sensitivity integral theorem is a valuable tool for analyzing control systems, as it can indicate the presence of the waterbed effect. This phenomenon suggests that the sensitivity of controllers to disturbance estimation may worsen at certain frequencies. As such, it is crucial to consider this effect when selecting the appropriate discretization method for analyzing and designing digital DOB-based control systems. In this study, we analyze the performance of DOB-based cascade PI-PI speed control systems in the discrete-time domain, which provides a more comprehensive understanding of the dynamic responses of digital motion control systems compared to continuous-time analysis methods. Our theoretical and experimental analyses demonstrate that the choice of acceleration and speed measurements, as well as the selection of discretization methods for DOB synthesis, significantly impact the stability and performance of digital motion controllers.