A Gain Scheduled Robust Regulator For Sinusoidal Ripples Elimination Of AC PM Motor Systems

This thesis addresses the problem of the elimination of torque and velocity rip-ples in the Alternating Current (AC) Permanent Magnet (PM) motor control systems,especially that of the sinusoidal disturbances.For the purpose of designing a simple but effective controller, the torque ripplescaused by DC offsets and phase gain error are studied and formulated mathematically.Firstly, the ripples generated by the offset currents are discussed. Secondly, the ripplesgeneration are analyzed thoroughly when the current gains of the motor drivers are dif-ferent between phases. The torque ripples can be modeled as two sinusoidal functionswhose frequencies depend on the motor speed. The internal model principle (IMP) isthen used to design a controller to eliminate the torque and velocity ripples withoutestimating the amplitude and the phase values of the sinusoidal disturbances. A gainscheduled (GS) robust two-degree-of-freedom (2DOF) speed regulator based on theIMP and the pole-zero placement technique is developed to eliminate the torque andvelocity ripples and to achieve a desirable tracking response. When the sinusoidal dis-turbances have varying frequencies, the stability radius of the system can be derivedwith the small gain theorem. Finally, we show that this regulator design algorithmcan be generalized to eliminate any number of sinusoidal torque ripples with knownfrequencies in AC PM motor system.Simulation shows that the GS robust 2DOF speed regulators based on the IMPand pole-zero placement technique can effectively eliminate the sinusoidal distur-bances. If the acceleration profile is available for the GS controller, the stability radiuscan be enlarged.