Improved Particle Swarm Optimization Algorithm Based Driving Strategy Research for Permanent Magnet Spherical Motor

A permanent magnet spherical motor (PMSpM) is a compact transmission apparatus that is capable of motion in multiple degrees of freedom. To achieve the close loop control of the PMSpM, the driving current of the stator coils needs to be calculated, and the analytic torque model needs to be built in advance. However, if the geometry of the permanent magnet (PM) is a non-circumferential symmetric one, the pseudo-inverse matrix technique is not applicable. Thus, the research on the fast driving strategy of the universal reverse torque model is an essential prerequisite for the PMSpM close-loop control. This paper takes the PMSpM with the stepped cylindrical PM as the research object. Firstly, this paper proposes new analytical torque models using the toroidal expansion method. To avoid repeating integrations in magnetic and torque analytic calculation, this paper builds torque maps by moving one 1A energized electromagnetic coil on the overall spherical surface of the airgap along the azimuth angle direction and polar angle direction. Secondly, the classical particle swarm optimization algorithm (PSO) is introduced to build the reverse torque model. The current of the stator electromagnetic coils is considered as the particle swarm, and the desired torques are set as optimization targets. Thus, we can use the reverse torque model to calculate the driving current of the stator electromagnetic coils from the torque maps. Thirdly, this paper proposes an improved particle swarm optimization (IPSO) algorithm for the PMSpM driving strategy optimization, which can be used for calculating the real-time driving current for the desired torques of the PMSpM. After the determination of the population size of the PSO algorithm, the adaptive dynamic inertia weight and adaptive learning factors are introduced for IPSO. Simulation results on the IPSO algorithm optimization show that the improvement of the classical PSO algorithm is significantly effective. A typical population size can generate convergence before 250 iterations. The larger the population size, the more concentrated the convergence curves. A bigger population size illustrates the robustness of the PSO algorithm, but it also needs more convergence time. Thus, to balance the current calculation algorithm convergence rate, this paper adopts popsize = 30 . With the same convergence precision, the PSO algorithm © 2023 Chinese Machine Press. All rights reserved.