Transient Characteristics Analysisof PM Spherical Motor Based On The Finite Element Method

With the rapid development of robotics and other high-technology, the PM spherical motors which can achieve three-degree-of-freedom (3-DOF) motion become a hot topic. At present, the research on the PM spherical motors are still in theory exploration stage and limited in the fields of electromagnetic, mechanics decoupling control, trajectory tracking and so on. The researches on the aspects of the magnetic field are mainly confined to the static characteristics of the PM spherical motor, which cannot display a complete picture of the performance of the PM spherical motor. It restricts the research progress of spherical motor control greatly. The start-performance and changes in motor’s performance caused by the mutation load of the PM spherical motor are important research content. These aspects are all the categories of the dynamic characteristics analysis of the PM spherical motor. Little literature can be found about the transient characteristics of the PM spherical motor. This paper shows a preliminary study of the transient performance of the PM spherical motor.This paper puts the two-dimensional (2-D) equivalent model of the PM spherical motor as a research object, and analyses the transient characteristics of the PM spherical motor based on2-D finite element method. This paper builds the2-D finite element equivalent model of the PM spherical motor. By controlling the stator windings split phase, it gets the results of the PM spherical motor rotation reluctance torque, no-load back EMF and no-load flux of2-D transient characteristic curve. In this paper, the influences of different parameters on the motor for rotation reluctance torque, no-load back EMF and no-load winding flux transient characteristics are also discussed.In order to more fully demonstrate the dynamic performance of the PM spherical motor, the2-D is extended to3-D. The3-D finite element equivalent model of the PM spherical motor is built, split phase the stator windings according to certain energized strategy. First, it gets the3-D transient characteristic curves of the rotation reluctance torque, the no-load back EMF and the no-load flux of the PM spherical motor by testing the PM spherical motor no-load transient characteristics. Then, the transient characteristic of PM spherical motor with load is discussed. A three-phase bridge outside the circuit is built in finite element method. The stator coils are energized by a certain strategy. The starting performance of the rotation speed and rotation torque of the PM spherical motor is studied. This paper also discusses the affect of different parameters of motor on the no-load3-D transient characteristic of the rotation reluctance torque, the no-load back EMF and the no-load flux of the PM spherical motor, which founds the theoretical basis for the further optimization of the PM spherical motor.The efficiency of the PM spherical motor is also an important constraint condition of the motor optimization design. This paper is a preliminary study on the efficiency of the PM spherical motor. The permanent magnet eddy current loss is analyzed using the finite element method under no-load condition. The paper also tests the affect of the different magnetization of the permanent magnet, different parameters of the motor structures and different speed on the permanent magnet eddy current loss.