# An NUTSF at Sub-Region for Suppression of Torque Ripple in Switched Reluctance Motors
## 5 Simulation Analysis  
A 6/20 pole SRM model and its control system were built in MATLAB/Simulink based on the above theoretical analysis, and the effectiveness of the control strategy was verified. The simulation model is shown in Figure 11. The specific parameters of the 6/20 pole SRM are shown in Table 2. The instantaneous phase torque was obtained by using the lookup table in the simulation model.  
Figure 11: Simulation model of SRM and one-phase NUTSF simulation model.  
The conventional exponential TSF and the proposed TSF control strategy were adopted in the simulation model, respectively. The load torque was set to 5 N\(\cdot\)m, and the SRM operated at 500 r/min and 1000 r/min, respectively. The torque ripple rate \(K_{r}\) was defined to compare the performance of the two control strategies. The expression is as follows  
\[K_{r}=\frac{T_{\max}-T_{\min}}{T_{av}}\times 100\% \tag{11}\]  
where \(T_{\max}  
The simulation result shown in Figure 12 demonstrates that when the SRM operates at 500 r/min, the total torque ripple of the two control strategies of the conventional exponential TSF and NUTSF is relatively small, but the NUTSF control strategy plays a better role in suppressing torque ripple. As shown in Figure 12a, at the start of the two-phase exchange region (region 1), the torque sharing function curve of the incoming phase of the conventional exponential TSF control strategy has a larger change rate (steeper shape) and the phase torque reference is larger. However, at the start of the two-phase exchange region, the smaller the change rate of the incoming phase inductance is, the smaller the actual incoming phase torque will be, resulting in the actual incoming phase torque being less than the incoming phase torque reference and the larger torque ripple will be. The torque of the conventional control strategy is between 4.7 and 5.75 N\(\cdot\)m.  
As shown in Figure 12b, the shape of the TSF is adjusted in the NUTSF control strategy according to the optimization algorithm of the TSF in the two-phase exchange region. The torque reference of the incoming phase increases slowly, and that of the outgoing phase decreases, which is more in line with the changes in the actual torque of the incoming phase and the outgoing phase, and the effective reduction in the torque ripple in the TpE. The torque of the NUTSF control strategy is between 4.76 and 5.5 N\(\cdot\)m.  
The waveforms of the phase current, the torque of each phase and the total torque obtained by the two TSF control strategies are shown in Figure 13 when the SRM operates at 1000 r/min. The simulation results show that the torque ripple of the conventional exponential TSF control strategy becomes larger when the SRM operates at 1000 r/min, while that of the NUTSF control strategy is still smaller. As shown in Figure 13a, with the increase in speed, the interval time of the two-phase exchange is shortened, and the conventional control strategy needs to make the incoming phase torque rise to a larger torque reference in a shorter time. However, the actual inco  
Figure 13: Simulation waveforms of torque and current: (**a**) conventional TSF scheme at 1000 r/min; (**b**) proposed NUTSF at 1000 r/min.  
quickly rise to the torque reference due to its low change rate of the inductance at this stage and the larger error between the two results in a larger torque ripple. The torque of the conventional control strategy is between 4.21 and 7.28 N\(\cdot\)m.  
As shown in Figure 12(b), the shape of the TSF is adjusted by the NUTSF control strategy in regions 1 and 2 in the TpE, which reduces the error between the torque reference and the actual torque, and effectively reduces the torque ripple, which is between 4.75 and 5.63 N\(\cdot\)m in TpE.  
By analyzing and comparing Figures 12 and 13, it can be clearly seen that the NUTSF control strategy has better suppression capability of torque ripple when the SRM operates at different speeds.