# Optimization Design and Control of Six-Phase Switched
###### Abstract  
In this paper, a design optimization method is proposed to reduce the current asymmetric and consequent torque ripple for a six-phase Switched Reluctance Motor (SRM). First, the inconsistent current phenomenon of the investigated SRM is introduced, and the relationship between the magnetic distribution and the phase currents is investigated by magnetic circuit analysis. Then, for the reduction in computational cost, a surrogate model is utilized to establish the response surface model between the optimization objectives and variables. Furthermore, multiobjective optimization is performed based on structural design optimization and asymmetric control, and the best design solution is selected for the drive system. Compared with the traditional symmetric control, it can be found that the proposed asymmetric control can mitigate the inconsistent phase currents and reduce the torque ripple. Finally, a prototype motor is manufactured and tested. Both the simulation and experimental results verify the effectiveness and the reasonability of the analysis and the optimization.  
finite-element model (FEM); multiobjective optimization; switched reluctance motor +
Footnote †: journal: Applied Sciences  
-state/rotor poles SRM under the two magnetic pole distributions are investigated, and a new method was proposed to reduce torque ripple by setting different current chopping limits [24]. In [21], possible winding arrangements for six-phase SRMs are presented and analyzed. Moreover, in [25], the combination of magnetic poles under different conduction modes was proposed, and the influence caused by the winding connections on static torque was further investigated. Through the comprehensive comparison of different winding connections, it has been found that the NNSS alternating winding arrangement exhibit the best overall performance; however, at the same time, asymmetry current phenomenon occurs in the six-phase SRM [21; 26].  
In summary, there is a coupling phenomenon between the phases when the winding connection method with reverse series was applied in the even-numbered phase SRM, which reduces the fault-tolerant ability of SRMs. Moreover, the magnetic field distribution of the system will be asymmetric if the decoupling winding connection is utilized, leading to the asymmetry of the phase currents in the even-numbered phase SRM. This will further increase the torque ripple of the system [27; 28].  
In this paper, a novel multiobjective optimization method incorporated with an asymmetric control is proposed to reduce the inconsistent phase currents and consequent torque ripple for a six-phase 12/10 SRM. The main contributions of this paper are listed as follows.  
1. The asymmetric current phenomenon for the investigated SRM is introduced and explained by the magnetic circuit analysis.
2. A novel system-level multiobjective optimization method is proposed by considering the structural variables and the turn-on angles and conduction width in the proposed asymmetric control.  
The remainder of this paper is organized as follows. In Section 2, the current asymmetry caused by the forward series winding connection is investigated and its influence on torque ripple is analyzed. Section 3 describes the applied surrogated modeling method. Then, in Section 4, a system-level multiobjective optimization is proposed to reduce the current asymmetry and torque ripple of the drive system. Results and experimental verification are presented in Section 5, followed by the conclusion in Section 6.