Torque Ripple Suppression of Building-Block Transverse Flux Permanent Magnet Motor by Current Compensation and Variable Parameter Control Based on Real-Time Inductance

Abstract

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.

A Review of Transverse Flux Machines Topologies and Design

“…TFMs potential for vehicle traction has been explored, for example, in hybrid buses [84], ships (200 MW, 200 rpm per shaft, directly-coupled) [83], as an in-wheel motor for electric scooters [6,90,93], bikes [56] and for other in-wheel uses [25,87,88,92]. It has been shown that the efficiencies of a TFM and a RFM are comparable in the low-speed-low-torque operating point, and better for the RFM in the high-speed point and for the TFM in the high-torque point [85].…”

“…Cogging torque compensation by control strategies benefits from a better adaptation to different TF topologies, because the machine structure is not modified in any way. A current compensation control has been reported in [92], based on seven nonlinear dynamic models involving the relationship among main motor parameters, and these parameters are fitted in real time and the torque is calculated by 3D-FEM. The torque ripple is reduced and the average torque is even improved.…”

“…Dynamic compensation control (of current) with adaptive parameter correction (of the strand inductance) for a TF generator is proposed in [71], a recursive least square algorithm is used for this purpose. A similar approach ("current compensation method and variable parameter PID algorithm based on real-time inductance") has been presented in [92] for a 5-phase TF motor to reduce the torque ripple. A predictive current control strategy is adopted in [133].…”

“…where T max , T min and T avg are the maximum, minimum and average torque. In many TFM studies, the torque ripple analysis is basically focused on the cogging torque, but the synchronous torque and reluctance torques are equally relevant contributions to torque ripple [92]. However, cogging torque is the only component that is present with no stator current (and it has zero average value, as shown in Figure 14 [93]), so it has a specific influence in the machine start up (e.g., wind turbine applications) [67].…”

“…Changing the machine structure (PMs, stator or rotor) usually requires various 3D-FEM calculations, thus increasing significantly the calculation time. The resulting topology is often more complex, so the manufacturing process gets more difficult and the machine cost is higher [92].…”