STABILITY AND PERFORMANCE ENHANCEMENT OF DIGITAL DISTURBANCE OBSERVER WITH APPLICATION TO PERMANENT MAGNET SYNCHRONOUS MOTORS

Abstract

There are different control systems for dealing with diverse disturbances and uncertainties in engineering applications such as robotics and mechatronics, as well as electronics. After Ohnishi discovered it in the middle of the 1980s, disturbance observer (DOB) became one of the most prominent control approaches. PM synchronous motor type is widespread in a variety of areas and offers several benefits, such as a high power factor, high efficiency, robustness, and rugged construction. Despite the fact that robust motor controllers are always implemented with microcontrollers and computers, continuous-time analysis methods are widely used due to their simplicity. The dynamics of disturbance estimation, or designing disturbance obsever’s parameters, have a significant effect on the stability and performance of the robust motor controller system. However, analysis in continuous time domain using Bode Integral Theorem, which is usually employed for the understanding stability of the control system, does not provide full information about stability. Focus of this research is analysis the stability of a Speed based Disturbance Observer for Permanent Magnet Synchronous Motors in the discrete-time domain by applying ten different discretization approaches. The research will show the analysis and selection of appropriate discrete time method for the motion control system with the application to PMSM. Simulation and experimental results shows that some of the discretization approaches provide better stability and performance than others. This thesis shows that the choice of a discretization method can significantly impact the stability and performance of a control system.