Flux reversal linear-rotary permanent magnet actuator (FR-LRPMA) is a novel electromagnetic actuator integrating the features of flux reversal principle and linear-rotary permanent magnet actuator, which can achieve the rotary, linear or spiral motion. It can be widely used in the industrial field, robotics and aerospace and other fields. Therefore, it has greatly theoretical significance and practical engineering application value in the design and drive control field.
In the paper, the state of linear rotary actuator (LRA) is analyzed, the different topologies and performance characteristics of all kinds of LRA are compared. Then the control principle of the LRM is analyzed and summarized. A FR-LRPMA topology is proposed, and its basic working principle and main electromagnetic parameters are studied. The inductance and flux linkage characteristics of FR-LRPMA are analyzed by the linear model, and it is verified by 3-D finite element method.
Based on the equivalent curvature coefficient method, an analytical method is used for the no-load air-gap magnetic field. Assuming that the stator and the mover are slotless, the tubular structure can be transformed to a planar one, 3-D analytical magnetic field is calculated in the Cartesian coordinate system, and then the curvature coefficient is calculated to reduce the error between the analytical magnetic field in the plane model and the tubular model. The relative air permeability is calculated, which can consider the influence of the permanent magnet pole and the ferromagnetic pole in the air gap magnetic field and the influence of the stator slot and the mover slot on the air gap magnetic field, and then the no-load air-gap magnetic flux density is obtained. Based on the Maxwell stress tensor method, the analytical function of the cogging torque and the linear positioning force is derived. The virtual power method is used to derive the analytical function of the torque and thrust and optimize the topology structure.
According to the mechanism of irreversible demagnetization and the demagnetization model of the permanent magnets, the main demagnetization factors of the permanent magnet material of FR-LRPMA are analyzed. The fitting function is proposed, which takes the current, the mover position, temperature and permanent magnet thickness in consideration. The optimized value of permanent magnet thickness and the maximum current value is obtained, which avoids the possibility of irreversible demagnetization of permanent magnet.
The difference of control model between the flux reversal machine and traditional permanent magnet synchronous motor is analyzed, and the mathematic model of FR-LRPMA in the nine-phase stator coordinate system and mover coordinate system is built. According to the double dq coordinate system and space vector pulse width modulation, a simulation model of the control system is built in the Matlab/Simulink software, and then the simulation analysis is carried out.
A prototype is manufactured and the drive control system is constructed using DSP. The experimental system is built and the control system software is programmed. The main performance parameters of the prototype is tested, which verifies that the analytical method is correct. Based on the double dq transform, the mathematical model is achieved, which lays a theoretical and experimental foundation for the further theoretical research and the engineering application.