Abstract
A segmented control model including an improved sliding model control (SMC) and a speed compensation model is applied into the speed control of a segmented permanent magnet linear synchronous motor (PMLSM) to improve the speed precision during the drive process and reduce the speed loss during the switch process. During the drive process of segmented PMLSM, an improved SMC with a disturbance observer (DOB) is used to suppress the speed fluctuation, and a DOB is added to suppress the oscillation caused by the switch part of SMC. During the switch process of a segmented PMLSM, a speed compensation model based on the position feedback of permanent magnet (PM) actuator is designed to reduce the speed loss of a segmented PMLSM, so the speed of PM actuator could be kept at the reference speed when the PM actuator absolutely quits the stator windings. Finally, the simulation and experiment are conducted to verify the control performances of proposed control model, the results indicate that the speed fluctuation of PM actuator and the speed loss during the switch process are mitigated. Therefore, this proposed control model could satisfy requirements of high-stability and celerity of segmented PMLSM in a long-distance automatic transportation system.
Highlights
The permanent magnet linear synchronous motor (PMLSM) is widely applied in long-distance automatic transportation systems because of its advantages of high-speed precision, strong reliability, fast response and great power density [1,2,3]
Every stage stator is independently controlled by the main control unit (MCU) when the PM actuator is located on the upside of stator windings during the drive process [7], and the PM actuator would slide on the stator part during the slide process and the switch process
Where x is the actual position of PM actuator, la is the length of PM actuator, ls is the length of stator, ψf is the flux linkage of stator winding when the PM actuator is at the drive process and ψfin(x) and ψfout(x) are the flux linkage when the PM actuator moves in and out of stator winding, respectively
Summary
The permanent magnet linear synchronous motor (PMLSM) is widely applied in long-distance automatic transportation systems because of its advantages of high-speed precision, strong reliability, fast response and great power density [1,2,3]. The effective area between the stator winding and the PM actuator is constant, so the speed fluctuation is introduced by the load friction, the parameter perturbation and the detent force. For the purpose of suppressing the influences of uncertain thrust force on the speed control of a segmented PMLSM, the sliding model control (SMC) is used to suppress the fluctuation on thrust force of a segmented PMLSM considering its insensitivity on external disturbance and parameter variation, and a DOB is added to suppress oscillation caused by the switch part of SMC model in this article. During the switch process of a segmented PMLSM, one part of PM actuator is still located in the stator winding, but another part of PM actuator had moved out of stator winding, so the variation of effective action area would lead to the variations of EM parameters and thrust force [27].
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