Performance-oriented Robust Adaptive Control Of Brushless Direct Current Motor

Brushless direct current(BLDC)motor is a mechatronics product that includes electric motor technology,power electronics,control theory,computer technology and other science and technology.BLDC motor is developed on the basis of brush DC motor.Therefore,BLDC motor not only possesses the satisfying speed control performance,but also it has solved the problems generated by the mechanical commutation and the brush.Based on these advantages,BLDC motor has widespread applications in wide range of areas recently.In this thesis,we regard the performance of the BLDC motor as the research plant,analyze the angular velocity control and torque control of the BLDC motor and design control laws for them,respectively.The main contents of this thesis are as follows:First of all,based on the structural features and mechanics of the BLDC motor,the basic structure,basic principles and driving modes of the BLDC motor are introduced.Then taking the bipolar three-phase BLDC motor as an example,the equations between phase voltage and phase current,resistance,inductance of the BLDC motor are constructed.On the basis of the operating features of the BLDC motor,the equation of the motor voltage is transformed from three-phase coordinate system to two-phase coordinate system.In the two-phase coordinate system,the mathematical model and basic equations of the BLDC motor are constructed,which lay the theoretical foundation for the following analysis and design of the angular velocity control law and torque control law of the BLDC motor.Secondly,for the speed control of the BLDC motor,two adaptive control methods for the BLDC motor disturbed by two diverse kinds of external disturbances are proposed in this thesis.The dynamic model of BLDC motor possessing parametric uncertainties and disturbed by unknown with known bound external disturbances or disturbed by unknown with known structure model external disturbances is considered,respectively.1)For the BLDC motor system with parameter uncertainty and disturbed with known bound external disturbance,a robust adaptive control method based on backstepping is designed firstly.This method considers the prior knowledge of the parametric uncertainties and the bounded functions of external disturbances of the BLDC motor system.By means of the proveness and analysis of the robust adaptive law,the stability of the BLDC motor system has been guaranteed;2)For the BLDC motor system with parametric uncertainties disturbed by external disturbances with known structure model,an adaptive control method combined with disturbance observer isproposed.The unknown external disturbance is estimated by the disturbance observer and its estimate value is integrated with the control law.The resulting control law can estimate the external disturbance and reject it well,and the rotor speed of the BLDC motor system can track its desired value with satisfying performances.Also,simulation results verify the effectiveness of the proposed method.Thirdly,for the torque control of the BLDC motor,the BLDC motor system with parameter uncertainty and disturbed by external disturbance with unknown information is considered based on the proportion between phase current and torque.Also,the uncertainties can cause torque ripple in the BLDC motor system.In this thesis,the external disturbance is assumed to be sinusoidal with completely unknown phases,amplitude and frequencies,but the number of distinct frequencies or the order of the corresponding unknown linear exosystem is known.Based on this situation,the adaptive internal model method is proposed for the BLDC motor system.For the disturbance-free BLDC motor system,a baseline control law is designed to guarantee the stability of the disturbance-free BLDC motor system;for the disturbed BLDC motor system,an internal model method to estimate the external disturbance is proposed in this thesis.Combined the baseline control law with the estimate disturbance,the ultimate control law can reject the external disturbance and guarantees the torque of the BLDC motor track its reference signal asymptotically.Simulation results verify the effectiveness of the proposed methods.Finally,the research is summarized and some further researches to be explored are pointed out.