In order to improve the torque characteristics of the motor, many scholars and research institutes have made bold attempts and innovations in the structural design of permanent magnet synchronous motors, and many new advances have been made. In order to solve the contradiction between slot width and tooth width, transverse flux machine (transverse flux machine) technology is developed, where the armature coil and tooth slot structure are perpendicular in space, and the main magnetic flux circulates along the axial direction of the motor, which improves the power density of the motor; and the adoption of a double-layer arrangement of permanent magnets improves the motor's cross-axis conductance, which increases the motor's output torque and maximum power; The stator tooth shape and pole shape are changed to reduce the torque pulsation of the motor, etc.
With the use of weak magnetic control, the operating characteristics of permanent magnet synchronous motors are more suitable for the driving requirements of electric vehicles. With the same power requirement, the inverter capacity is reduced and the efficiency of the drive system is improved. Therefore, permanent magnet synchronous motors for electric vehicle drive commonly adopt weak magnetic speed expansion. For this reason, research institutes at home and abroad have proposed various schemes, such as the use of a double-set stator structure with different windings at different speeds to maximize the use of the permanent magnet magnetic field; the use of a composite rotor structure, where a reluctance section is added to the rotor to control the reactance parameters of the motor 's straight and cross axes to increase the motor's speed expansion capability; and the use of a deep slot in the stator to increase the straight-axis leakage resistance to expand the motor's speed range.
Due to the nonlinear and multivariable characteristics of permanent magnet synchronous motors, their control is difficult and the control algorithms are complex, and the traditional vector control methods often cannot meet the requirements. For this reason, some advanced control methods are applied in the permanent magnet synchronous motor speed control system, including adaptive observer, model reference adaptive, high frequency signal injection method and intelligent control methods such as fuzzy control and genetic algorithm. These control methods do not depend on the mathematical model of the control object, have good adaptability and robustness, and have unique advantages for systems with strong nonlinearity such as permanent magnet synchronous motors.
