| In this paper, the permanent magnet motor drive systemof contra-rotating propeller for marine equipment under water, such as underwater vehicle and ships, is studied. The system uses anaxial permanent magnet motor with counter-rotating rotors. The motor has two independent permanent magnet rotor, by inside and outside nested output shaft, driving the two contra-rotating propeller blades, respectively. The motor has only one stator and one three-phase winding, only need one driver to drive. Compared with the existing contra-rotating propeller drive system, the axial permanent magnet motor with counter-rotating double rotors, studiedin this paper, has a compact structure, small volume, light weight and low cost advantages. Although some scholars studied the similar motor drive, but there are a lot of key problems to be solved, such as motor’s back-EMF, torque characteristics when the two permanent magnet rotor in asynchronous. In addition, because only a three-phase winding and a three-phase driver, how to ensure that two rotor is able to run synchronization, and guarantee the stability of the system and so on, when there are unbalanced loads or disturbance in both the rotor, has no good solution yet.In order to solve the problems of theaxial permanent magnet motor with counter-rotating rotors and its control, promote the development of this kind of technology and application, this paper investigates into issures of design of such motor and characteristics of it, to further grasp the principle and characteristic of the special motor, at the same time solve the problem of the motor control.The main research work and achievements of this paper are as follows,(1) Research status and development trend for the object studied in this thesis has summarized systematically, main problems of the machine and its control have been puted forward, which provides reference and basis for the research of this paper.(2) Theoretical analysis of the motor design has been carried on, a simplifed temperature rise of the motor model is established, so to obtain the relation between the temperature rise and winding electric load of the winding. Combined with the selection of magnetic load as well as related to the existing research results, obtained the relationship between motor design power and outer diameter, provides reference for this type of permanent magnet motor design.(3) No-load magnetic field of the motor has been analyzed based on the analytical modeling, the maxwell characterization equation in the air gap and internal magnetic field of permanent magnet was established by using Fourier series and the method of separation of variables, the corresponding flux density analytical expressions are obtained. Using Fourier series and the method of separation of variables to the motor air gap and internal magnetic field of permanent magnet maxwell characterization equation, the corresponding flux density analytical expressions are obtained. Using the analytical expressions the magnetic field of the motor was analyzed, and the analytic calculation method for the motor back-EMFwas obtained, at the same time, the finite element resultswere compared with analytical expressions for the validation of usefulness.(4) Basic operation characteristics of the motor are analyzed, the back-EMF and torque characteristics during the two permanent magnet rotorsare in synchronous and asynchronous were analyzed, so to obtain the distortion characteristics of back emf with the two rotor asynchronous.The influence of the distortion characteristic for torque was also pointed out in this thesis. The stator magnetic field change characteristics is analyzed in different rotor state. According to the law of the magnetic field distribution, it is pointed out that this type of motor stator can be modular, so as to make munfacture of the winding simple. Also analyzed the influence the nonuniform axis of the crossing toroidal winding on the torque, and pointed out that the lap winding can reduce the torque ripple. The size and distribution of the axial electromagnetic force in the no-load and rated load cases was analyzed,also the lorentz force of the stator winding, and pointed out that compared with the axial magnetic force, the lorentz force of the winding in design can be ignored.(5) The operation characteristics of the motor under unbalanced load was analyzed, and pointed out that the existing control methods can’t guarantee synchronous ofthe two rotor, and a dynamic master-slave control method proposedinthis paper, to ensure the stability of the systemduring unbalanced loads or disturbance, and puts forward a reliable method of starting the motor. A rotor position identification method was proposed based on the sliding mode observer and the position of the other rotor, which is measured from a resolve. Preliminary simulation analysis verified the above methods and theories.(6) A simple and feasible test method was put forward, and developed an 2.2 k W prototype,the correctness of the design and analysis of the motorwas verified. At the same timethe effectiveness of the proposed control strategy in load imbalance or load disturbance was verified and the motor can be started in a reliable way.The problem of the control of two independent permanent magnet rotor with a three-phase driverwas solved. |
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