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Building-block transverse flux permanent magnet motor (B-TFPMM) has the advantage of electromagnetic decoupling and high torque density, but it has the strong nonlinearity and the large torque ripple. To solve the problem, the nonlinear characteristics of B-TFPMM stator back electromotive force (EMF) e pm , winding inductance L and single-phase torque T sp are analyzed firstly, and the nonlinear dynamic models involving e pm , L, T sp , stator current and rotor position are established by three-dimensional finite element method (3DFEM). Secondly, apply the square wave current and sinusoidal current to stator windings respectively, and the result shows that using sinusoidal current would acquire smaller torque ripple rate when the load torque is more than 30 N • m. Furthermore, the variation rule of five-phase current utilization is obtained and the maximum current utilization model is established. Based on these, the current compensation method is developed and then the torque ripple rate could be reduced by 10% approximately. After that, combining with 7 nonlinear dynamic models of B-TFPMM, a closed-loop control system based on the compensation method and variable parameter PID algorithm is built. The ratio of the real-time winding inductance to sampling period is chosen as the proportional coefficient of controller. The results indicate that compared with the control mode which combining uncompensated current and traditional constant parameter PID algorithm, the control mode of using compensated current and variable parameter PID algorithm would reduce the torque ripple rate by 57% to 65% and increase the average torque by 13% to 33% in the meantime. INDEX TERMS Building-block transverse flux permanent magnet motor, torque ripple suppression, current compensation, nonlinear dynamic model, variable parameter control.

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Building-block transverse flux permanent magnet motor(B-TFPMM) has the characteristics of low-speed high-torque and small axial size, which is suitable as the hub motor of direct-driving electric vehicle. However, the torque ripple of B-TFPMM is large, which would affect the driving safety and riding comfort. To optimize the motor torque, the topological structure and working principle of B-TFPMM are analyzed firstly, and the analytical model of B-TFPMM torque ripple rate is derived. Then, two quantum genetic algorithms (QGAs) with different evolution processes are presented, an optimal individual selection scheme considering the torque ripple and the average torque simultaneously are proposed and the main motor sizes that affecting the torque ripple are optimized. The result shows that one of the strategies has more obvious suppression effect on torque ripple, while the other one has more obvious optimization effect on average torque. Therefore, the appropriate strategy could be selected according to the specific need.Keywords: Quantum genetic algorithm • Building-block transverse flux permanent magnet motor • Torque optimization • Motor design

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