| LFSPM motor is a novel brushless machine having magnets in the stator with doubly-salient structure.It not only offers high efficiency and high power density,but also has sinusoidal magnetic field like the conventional secondary PM linear motor and relatively low cost.The key theoretical and technical issues on a 3-phase stator-6-slot-17-pole LFSPM motor drive system and thrust fluctuation suppression are investigated deeply and systematically.Then,based on the A&D5435 system,the hardware and the software are designed for the control system.Moreover,the test of the LFSPM motors control system is carried out.This work lays a theoretical and technical foundation for further research and development of LFSPM motors in the applications of servo control,electric drives as well as electromagnetic launch.The research achievements of this thesis include the following aspects:1.The basic structure and working principle of the LFSPM motor is firstly explained.Based on the soft workbench of the Ansoft,the numerical calculation model of the LFSPM machine is built.Furthermore,the magnetic field distribution,winding inductance and EMF are calculated by FEA,and meanwhile,the cogging force model of the single-tooth is built by the Fourier method.2.The adoptions of the vector-control strategy in LFSPM motors are studied.The control system of the LFSPM machine,of which the structure is cascaded control structure of the servo system,is designed according to the LFSPM motors and the magnetic parameters.What is more,an adaptive control of LFSPM based on parameter identification is put forward.Additionally,a novel method based on the harmonic suppression algorithm was proposed to compensate cogging force,which has been verified by both simulation and experiment results.Finally,the effectiveness of the control system is verified by the simulation and the test.3.Firstly,a novel initial rotor position estimation method was presented by injecting high frequency low voltage pulses for LFSPM motors.Then,by using the nonlinear magnetization characteristics of the stator core,a space voltage pulse width modulation algorithm is adopted to assess the initial position estimation of a LFSPM.Finally,it realizes the position detection of LFSPM motor under the zero velocity condition.4.A compound control strategy was proposed for position sensorless vector controlled LFSPM.Beyond that,the control strategy combined back-EMF with high frequency voltage signal injection to achieve wide speed range operation.Meanwhile,switching process between two control methods is put forward,and the accurate tracking to the position signal can be achieved for the closed loop system under the control of extended state observer.5.Based on repetitive control of time-varying periodic signals,a new method of restraining cogging force for LFSPM is proposed,and meanwhile,nonlinear feedback controller is designed.Since the convergence error will gradually decrease with the increasing of periodic numbers,the global asymptotic stability is thereby ensured.As shown by the simulation and experiment results,the control scheme is effective.6.The electromagnetic parameters,which are calculated by FEA,are embedded into the Matlab/Simulink model.Based on the real-time A&D5435,a digital drive and control experimental platform of LFSPM motor is built,which includes the multi-level comprehensive protective circuit on the basis of software and hardware. |
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