Multi-objective optimization of PMSM rotor structure based on stratified optimization strategy
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摘要:
永磁同步电机对转矩输出的平滑性有较高要求. 内置式永磁同步电机受齿槽转矩、磁阻转矩脉动、电磁转矩脉动等因素影响,输出转矩脉动相对较大,增加了电磁噪声和输出的不稳定性. 基于一台20 kW永磁同步电机建立有限元模型,验证模型的准确性. 以电机最大输出转矩、最小转矩脉动、最小齿槽转矩为优化目标,对电机转子结构参数进行灵敏度分析,并综合NSGA−Ⅱ算法和单变量参数法进行分层优化. 与单层优化相比,分层优化对易受变量影响的目标提升效果更好. 声学仿真验证了优化后的转子结构对电磁噪声改善效果显著.
Abstract:The permanent magnet synchronous motor (PMSM) has a high requirement on the smoothness of torque output. Due to influences of groove torque, reluctance torque pulsation, electromagnetic torque pulsation and other factors, the output torque pulsation of the interior PMSM is relatively large, which increases electromagnetic noise and output instability. A finite element model was established based on a 20 kW PMSM, and the accuracy of the model was verified. Taking the maximum output torque, the minimum torque pulsation and the minimum slot torque as optimization objectives, the sensitivity analysis of rotor structure parameters was carried out, and the stratified optimization was carried out by combining NSGA−Ⅱ algorithm and single variable parameter method. Compared with single-layer optimization, stratified optimization has a better effect on the target which is susceptible to variables. The acoustic simulation shows that the optimized rotor structure can improve electromagnetic noise significantly.
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表 1 样机参数
Table 1. Motor parameters
电机参数 参数值 极数 8 定子槽数 48 定子外径/mm 215 永磁体厚度/mm 4 额定电压/V 252 额定转速/(r•min−1) 2 000 气隙长度/mm 0.8 绕组类型 星型连接 表 2 电机主要结构参数初值及变化范围
Table 2. Initial value and variation range of main structural parameters of motor
结构参数 初值 变化范围 磁桥厚度H1/mm 3 2~4 槽机械角$\theta_{1} $/(°) 150 130~170 磁槽角度$\theta_{2} $/(°) 180 100~180 隔磁桥间距L1/mm 0 0~2 槽间间隔L2/mm 1 0.8~1.2 永磁体宽度W/mm 18 17.5~18.5 表 3 结构参数灵敏度分析结果
Table 3. Sensitivity analysis results of structural parameters
结构参数 输出转矩 转矩脉动 齿槽转矩 综合灵敏度 磁桥厚度$H_{1} $/mm −0.26 −0.58 −0.98 0.61 槽机械角$\theta_{1} $/(°) −0.29 −4.00 −7.61 3.97 磁槽角度$\theta_{2} $/(°) 0.22 0.56 0.47 0.43 隔磁桥间距$L_{1} $/mm −0.07 −0.11 −0.54 0.23 槽间间隔$L_{2} $/mm −0.01 0.46 0.63 0.37 永磁体宽度W/mm 0.51 6.07 10.22 5.65 表 4 高灵敏度参数Kriging模型预测精度
Table 4. Prediction accuracy of Kriging model with high sensitivity parameters
目标 ME(≤0.2) RMSE(≤0.2) $R^{2} $(≥0.9) $y_{1} $ 0.06 0.08 0.93 $y_{2} $ 0.06 0.07 0.93 $ y_{3} $ 0.07 0.07 0.94 表 5 高灵敏度参数优化方案
Table 5. Optimization scheme of high sensitivity parameters
结构参数 $H_{1} / \mathrm{mm} $ $\theta_{1} /\left(^{\circ}\right) $ $W / \mathrm{mm}$ $L_{1} / \mathrm{mm}$ $L_{2} / \mathrm{mm}$ $\theta_{2} /\left(^{\circ}\right) $ 初始值 3.0 150.0 18.0 0 1.0 180 优化值 2.4 158.8 17.6 0 1.0 180 表 6 高灵敏度参数优化结果
Table 6. Optimization results of high sensitivity parameters
参数 初始结果 优化结果 优化效果% $ T_{\mathrm{out}} / \left( \mathrm{N} \cdot \mathrm{m}\right) $ 100.94 103.73 2.8 $T_{\mathrm{ri}} /{\text{%}}$ 7.73 6.50 −15.9 $T_{\mathrm{cog}} / \left( \mathrm{N} \cdot \mathrm{m}\right) $ 1.40 0.43 −69.3 表 7 低灵敏度参数优化方案
Table 7. Optimization scheme of low sensitivity parameters
结构参数 $H_{1} / \mathrm{mm} $ $\theta_{1} /\left(^{\circ}\right) $ $W / \mathrm{mm}$ $L_{1} / \mathrm{mm}$ $L_{2} / \mathrm{mm}$ $\theta_{2} /\left(^{\circ}\right) $ 优化前 2.4 158.8 17.6 0 1.0 180 优化后 2.4 158.8 17.6 0 0.8 180 表 8 低灵敏度参数优化结果
Table 8. Optimization results of low sensitivity parameters
参数 初始结果 优化结果 优化效果% $ T_{\mathrm{out}} / \left( \mathrm{N} \cdot \mathrm{m}\right) $ 103.73 103.65 −0.1 $T_{\mathrm{ri}} /{\text{%}}$ 6.50 5.27 −18.9 $T_{\mathrm{cog}} / \left( \mathrm{N} \cdot \mathrm{m}\right) $ 0.43 0.22 −48.8 表 9 单层优化Kriging模型预测精度
Table 9. Prediction accuracy of single-layer optimized Kriging model
目标 ME(≤0.2) RMSE(≤0.2) R2(≥0.9) $y_{1} $ 0.03 0.04 0.97 $ y_{2}$ 0.06 0.08 0.92 $ y_{3}$ 0.05 0.06 0.95 表 10 分层及单层优化方案比较
Table 10. Comparison of hierarchical and single-layer optimization schemes
结构参数 $H_{1} / \mathrm{mm} $ $\theta_{1} /\left(^{\circ}\right) $ $W / \mathrm{mm}$ $L_{1} / \mathrm{mm}$ $L_{2} / \mathrm{mm}$ $\theta_{2} /\left(^{\circ}\right) $ 初始值 3.0 150.0 18.0 0 1.0 180 分层优化 2.4 158.8 17.6 0 0.8 180 单层优化 2.6 151.0 17.7 0.8 0.9 167 表 11 不同优化方案对比
Table 11. Comparison of different optimization schemes
参数 初始结果 分层优化 单层优化 结果 优化效果/% 结果 优化效果% $ T_{\mathrm{out}} / \left( \mathrm{N} \cdot \mathrm{m}\right) $ 100.94 103.65 2.7 101.30 0.4 $T_{\mathrm{ri}} /{\text{%}}$ 7.73 5.27 −31.8 6.75 −12.7 $T_{\mathrm{cog}} / \left( \mathrm{N} \cdot \mathrm{m}\right) $ 1.40 0.22 −84.3 1.28 −8.6 -
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