武汉理工大学毕业设计（论文）

电动汽车主动转向系统设计与研究

学院（系）： 国际教育学院

专业班级：车辆工程专业 1601班

学生姓名： 范钲文

指导教师： 陈词

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Abstract

With the development of the electric vehicle industry, drivers have been increasingly demanding on the performance of electric vehicles, such as handling stability, safety, comfort and sensitivity. Active front steering can superimpose an independent steering angle on the basis of the driver's steering angle input. In turn, the driver's steering intervention is realized, which optimizes the vehicle's response to the driver's input and improves the stability of the vehicle under emergency condition. When the vehicle is turning at low speed, it provides the driver with lightness and flexibility, and provides safety and stability when turning at high speed. Active steering system is the research hotspot and main trend of electric vehicle steering technology and active vehicle safety. The electric vehicle active steering system designed in this paper is based on some kind of traditional active steering system. By installing a double planetary gear mechanism and an active steering motor on the steering axle, combined with the research status at home and abroad, the following aspects of the system are studied.

（1）Several variable transmission ratio mechanisms are compared. By analyzing the structural characteristics of different mechanisms, a variable transmission ratio mechanism that is more suitable for electric vehicles is selected, and the structure and parameters are optimized based on this.

（2）The research analyzes the working principle and structural characteristics of the electric vehicle active steering system, puts forward the design idea of the electric vehicle active steering system, and designs the electric vehicle active steering system based on the double planetary gear mechanism and can realize the variable transmission ratio.

（3）The transmission mechanism of the active steering system of electric vehicles was designed and analyzed, and the structural parameters of these key components were optimized by establishing a kinematic model of double planetary gear And the turn ratio of the optimized steering system is analyzed to verify the feasibility of the steering system.

（4）The active steering system was structurally modeled through CATIA, which more intuitively showed the structure and working principle of the entire system; using the DMU module in CATIA to perform motion simulation analysis on the designed active steering system, confirmed the design The structure is feasible.

Key Words：Active Front Steering; Electric Vehicle; Variable Transmission Ratio; AFS

TABLE OF CONTENTS

Chapter 1 Introduction 1

1.1 Background 1

1.2 Variable Ratio Mechanism 2

1.2.1 Active Steering System 3

1.2.2 Direct Steering System 4

1.2.3 Wire-to-Wire Active Steering System 5

1.3 Related Research 6

1.4 Main Contents and Approaches 9

Chapter 2 Automotive Active Steering System Design 11

2.1 The Basic Principles of AFS 11

2.2 Compositions of AFS 13

2.3 Working Principle of the Transmission Parts in the AFS 14

2.4 The Rheological Model of the Two-Planet Gear Set 16

2.5 Optimizing Design 19

2.5.1 Chose Electric Motor to Replace Hydraulic Power System 19

2.5.2 Approaches to Parameter Optimization 20

2.5.3 Parameter Optimization of Transmissions 21

2.6 Summary 26

Chapter 3 Modeling Design of Automotive Active Steering System Drive Mechanism 27

3.1 Advantages of Computer Simulation 27

3.2 Establishment of Three-dimensional Model 27

3.2.1 Drawing of Key Parts 28

3.2.2 Parts Assembly 30

3.2.3 Motion Simulation 31

3.3 Summary 32

Chapter 4 SUMMARY AND PROSPECT 33

4.1 Main Research Results and Summary 33

4.2 Prospect of Research Work 34

REFERENCES 35

ACKNOWLEDGEMENT 37

Chapter 1 Introduction

1.1 Background

With the continuous increase of car ownership worldwide, environmental problems caused by the emission of car exhaust pollutants have received widespread attention, and the atmospheric environment on which humans depend is severely threatened. To this end, governments and automobile manufacturers of various countries have proposed to develop electric vehicles as a measure to solve this problem. Electric vehicles are different from traditional internal combustion engine vehicles in terms of power source, transmission mode, and structural arrangement..

The automobile steering system is an important subsystem composed of automobile structures. Its handling performance directly affects the safety, stability, sensitivity and driving comfort of the automobile. With the continuous development of electric vehicle-related technologies and vehicle control theory and technology, people are increasingly demanding the overall performance of electric vehicles. In order to improve the active safety and handling stability of electric vehicles, electric vehicle active steering systems It plays a key role in improving the overall performance of electric vehicles. In the traditional automobile steering system, it is impossible for the driver to actively correct and control the requirements of the operation stability according to the current vehicle operating conditions, and make up for the driver's improper steering operation. Therefore, the steering stability that is most closely related to the control characteristics and performance of the car cannot play its maximum role.

Given the traditional automobile steering system can not meet the requirements of modern electric vehicle steering system, today's society has aimed to research a new generation of electric cars, therefore, the requirements of the active steering system is increasingly urgent, and the main research focus on improving security and sensitivity. So to design a set of advanced combination of active steering function of the steering system is particularly important to improve the overall performance of electric cars. Therefore, the most cutting-edge research hotspots in the world today are focused on a new generation of steering technology with more excellent steering performance-automotive active front wheel steering system (the AFS).

In the traditional vehicle steering system, the transmission ratio is fixed when the vehicle is steering, and the safety and stability of the vehicle are poor. When the car is turning at a low speed, the driver not only steers the steering wheel with a large steering range, but also takes a lot of effort, and the driver's steering stability is greatly reduced. When the car is turning at a high speed, the steering sensitivity becomes greater, and the driver’s small steering angle of the steering wheel will produce a large lateral acceleration, which will cause the safety and stability of the car to be seriously reduced, which will cause inevitable contradictions. The traditional steering system maintains a compromise on two extreme situations. Therefore, how to improve and optimize the structure of the traditional steering system to achieve the driver's flexibility for low-speed steering and stability requirements for high-speed steering has become one of the hot issues in steering system research area ^[1].