| As the development of modern industry, requirement to control of induction motor is becoming higher and higher. However, it is difficult to meet because of two problems that the poor robustness to time-varying motor parameter exists in the common vector control system and the accurate mathematical model of induction motor is built difficultly. Therefore, the Linear Active Disturbance Rejection Controller (LADRC) is firstly used in the induction motor drive in this dissertation. LADRC has been developed based on Active Disturbance Rejection Controller (ADRC). This is not countermarch, should say, ADRC is an inevitable stage of LADRC. LADRC is proposed in order to solve the problem that ADRC has too many parameters and is difficult to tune. If LADRC is used in induction motor drive instead of PID, it not only meets the requirement to induction motor but also is convenient to engineering application.Because of the special structure, LADRC is not overly dependent on the accurate mathematical model of motor and can estimate and compensate the general disturbance that includes the unknown internal dynamics and the external disturbance by linear extended state observer, so the rotor flux decouples with torque completely and the complex control of inductor motor is simplified to the linear control. The result is the performance of the system is improved. Moreover, the stability of LADRC is proved.After analysis, it is found that positive and negative amplitudes ofα-axis rotor flux obtained by MRAS or ESO flux observer are not equal, andβ-axis rotor flux is the same, as a result, the total rotor flux has ripple. The reason is that MRAS and ESO flux observers are built inα-βCoordinate. Furthermore, the above flux observers are not robust enough to rotor resistance. The flux observer presented in this dissertation is in rotating reference frame. It is simple and inherently robust to rotor resistance. In addition, because this rotor flux observer and vector control based on LADRC are in rotating reference frame, coordinate Transformation is not needed between them, so the structure of the system is simplified.The induction motor drive with speed, rotor flux, d-axis and q-axis current loops is built based on LADRC and rotor flux observer. According to vector control theory and on the foundation of rotor flux estimation, we utilize the q-axis rotor flux converging to zero for speed estimation and a sensorless vector control induction motor drive is also built.To verify the performances of the above systems, A lot of comparative simulations were made with the induction motor drive using PID regulator under set point change, large inertia and rotor resistance variations, and external torque disturbance in MATLAB/SIMULINK. Simulation results show that the above control strategy has better static and dynamic performances, strong robustness to external torque disturbance and prarmeter perturbation, as well as simple structure , easy design and parameter tuning. All of these will make LADRC become a novel, practical and digital control technology.Lastly, LADRC is used in control system of ship elevator, which is a multi-motor control system. Simulation results show that LADRC can meet the requirements of ship elecator to smooth accelerating and decelerating control, load balancing control and redundant control.
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