Structural Analysis and Optimum Design of a 50kW DC Motor

本文提出電動車用50 kW直流馬達之結構分析與最佳化設計。馬達零件包含定子結構、前蓋、後蓋和盤蓋，定子結構包含外殼、定子矽鋼片和線圈繞組。馬達模型利用AutoCAD軟體建立實體模型，並轉換至有限元素軟體ANSYS建立有限元素模型。接著，透過有限元素之模態分析與實驗模態量測，獲得零件、次組合結構和完整馬達結構的結構特性。此外，藉由簡諧響應分析，計算出當定子矽鋼片的齒端面被施加電磁力時，馬達結構受電磁力作用之頻率響應。最後，利用最佳化方法改良重新設計的馬達結構之剛性。根據對於第一模態自然頻率具有較高敏感度比作為新馬達結構的設計變數。藉由給予的設計變數，發展一個新馬達結構之參數式繪圖程式建立實體模型。接著執行最佳化方法，改良新馬達結構的第一模態自然頻率並不增加原來的重量。比較原始設計，當馬達重量維持不改變時，最佳化設計的第一模態自然頻率增加2.2%。This thesis studies the structural analysis and optimum design of a 50 kW DC motor for electric vehicles. The motor components include stator structure, front cover, rear cover, and disk cover. The stator contains yoke, stator-core and windings. First, the solid models of motor components are established by CAD software AutoCAD and transferred to FEM software ANSYS for generating finite element models. Then, the structure characteristics of the components, subassemblies and entire assembly are analyzed by FEM modal analysis and verified with experimental modal testing results. In addition, the electromagnetic forces are applied to the teeth tips of the stator-core and the frequency responses of the entire assembly are calculated by FEM harmonic response analysis. Finally, the stiffness of the redesigned 50 kW motor structure is improved by using the optimum design method. Design variables of the new motor structure are selected according to larger sensitivity ratios of the first natural frequency. With given design variables, a parametric drawing program is also developed for establishing the solid model of the new motor. The structural optimization is performed to improve the first natural frequency and not to increase the original weight of the new motor. Compared to the original design, the first natural frequency of the optimum design is increased by 2.2%, while the motor weight is maintained unchanged.口試委員會審定書 II 致謝 IV 中文摘要 VI ABSTRACT VIII CONTENTS X LIST OF FIGURES XII LIST OF TABLES XVI LIST OF SYMBOLS XVIII Chapter 1 Introduction 1 1.1 Development and characteristics of IPMSM 1 1.2 Paper review 1 1.3 Research motivation 4 1.4 Outline 5 Chapter 2 Basic theories of structural analyses and optimum design 6 2.1 Theory of finite element structural analysis 6 2.1.1 Static analysis in finite element analysis 7 2.1.2 Modal analysis in finite element analysis 7 2.1.3 Harmonic response analysis in finite element analysis 8 2.2 Structural optimum design 9 2.3 Principle of vibration sensor 12 2.4 Theory of orthogonal material 14 Chapter 3 Structural analyses and modal testing of motor structure 15 3.1 Description of motor structure 15 3.2 Finite element model of motor structure 17 3.3 FEM modal analysis and experimental modal testing of motor structure 21 3.3.1 Convergence test 21 3.3.2 Introduction and experimental setup of modal testing 22 3.3.3 FEM modal analysis and experimental modal testing of components 23 3.3.4 FEM modal analysis and modal testing of motor subassembly 34 3.3.5 FEM modal analysis and modal testing of entire assembly 41 3.4 Harmonic response analysis of motor structure 46 Chapter 4 Structural improvement of new motor structure with optimization design 51 4.1 Sensitivity Analysis of New Motor Structure 52 4.2 Parametric drawing and analysis program of new motor structure 53 4.3 FEM modal analysis and harmonic response analysis of new motor 57 4.4 Structural optimization of new motor structure 63 4.5 Comparison between original and improved new motor structure 67 Chapter 5 Conclusions and suggestions 70 5.1 Conclusions 70 5.2 Suggestions 71 Reference 72 Appendix A Parametric Drawing and Analysis Program 75 Appendix B Optimum Design Program of New Motor 9