论文总字数：72055字

Graduation Project of Wuhan University of Technology (Thesis)

Electric minibus electric power system design

College (department) : School of International Education

Major class: Vehicle Engineering Major Vehicle gj1603 class

Student name: Wang Kai

Advisor: Yang Can

Statement of originality of dissertation

I hereby declare that the paper submitted is the result of my independent research under the guidance of my tutor. This paper does not include any other work that has been published or written by individuals or groups, except for those specifically cited. I am fully aware that I bear the legal consequences of this statement.

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June 20, 2020

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目录

Abstract 1

Chapter 1 Introduction 1

1.1 The introduction 1

1.2 The purpose and significance of the study 2

1.3 The research status 4

1.3.1 Research status abroad 4

1.3.2 Domestic research status 5

1.4 Research objectives and basic contents 7

1.4.1 The research target 7

1.4.2 The basic content 7

Chapter 2 Introduction of EPS system 7

2.1 Composition of EPS system 7

2.2 Classification of EPS system 10

2.3 The working principle of EPS system 12

Chapter 3 EPS system design of an electric minibus 12

3.1 Calculation of static steering resistance moment of wheels 12

3.2 Design and selection of steering gear 13

3.2.1 Selection of steering gear type 13

3.2.2 Steering gear ratio 14

3.2.3 Static in situ steering with no power on the steering wheel 15

3.2.4 Static in situ power when the steering wheel hand 15

3.3 Power motor selection and reduction drive mechanism design 16

3.3.1 Selection of power motor type 16

3.3.2 Motor rated torque 16

3.3.3 Motor rated power and rated speed 17

3.3.4 Motor rated voltage 17

3.3.5 Design and selection of reduction transmission mechanism 17

3.4 EPS power characteristic analysis 19

3.5 Torque sensor and speed sensor selection 23

3.6 The summary of this chapter 23

Chapter 4 Optimization design of steering trapezoidal mechanism based on MATLAB 24

4.1 An overview of the 24

4.2 Ackerman's principle 25

4.3 Analytical method is used to find out the actual relationship between inner and outer wheel rotation angles 25

4.4 Optimization design of steering transmission mechanism 27

4.4.1 The establishment of the target function 27

4.4.2 The design variables 28

4.4.3 The constraint 28

4.4.4 Establish optimization mathematical model 29

4.5 MATLAB optimization toolbox is used to solve 30

4.5.1 Determination of the objective function 30

4.5.2 Constraint function 30

4.5.3 Optimize function calls 30

4.6 Optimization result analysis 30

4.7 The summary of this chapter 32

conclusion 32

Thank you 33

reference 33

Attached to the record 35

Appendix A: 35

Appendix B: 35

Appendix C: 36

Abstract

Electric power steering is a kind of vehicle power steering technology which is provided by electric motors and controlled by ECU in real time.Applying it to the steering system of automobile can greatly improve the steering performance of automobile. According to the speed of different sizes of steering power, reduce parking and low speed driving control force, improve the steering characteristics and active safety performance at high speed driving. Good EPS control strategy can also make the steering system corresponding more quickly, which provides the possibility for the design of power steering system with excellent performance.

This paper takes electric minibus as the research object, and the ultimate goal is to design a set of electric power steering system with good performance. Firstly, the relevant knowledge of automobile design and mechanical design is used to determine the design process, and the reasonable support mode and trapezoidal layout mode are selected to design other parameters of automobile steering system. Then on this basis, Matlab is used to optimize the design of steering trapezoidal mechanism to obtain better steering performance. Finally, CAD drawing software is used to draw two-dimensional drawings of some parts, so as to complete the design of the entire electric power steering system.

This topic USES Matlab optimization and CAD design technology, the electric power steering power technology will be applied in the steering system of passenger cars, passenger cars steering power system design and development has a certain reference value.

Keywords: EPS system, Matlab, CAD, steering trapezoid, optimization design

Chapter 1 Introduction

• 1. The introduction

For vehicles with mechanical steering system, the driver needs to provide a large steering torque when turning in place and running at low speed. In order to solve the problem of over-steering, GM of the United States first applied hydraulic power steering system to cars in 1950s.However, hydraulic power steering system in guarantee more swiftly under the condition of the vehicle at low speed cannot satisfy the stability at high speed so Japan koyo company in 1983 developed a along with the speed of different produce different power of electronically controlled hydraulic power steering system, after the speed to speed up to provide this type of steering system of steering will gradually decrease, good balance in the lower speed steering portability and stability under high speed, but its complex structure, high cost, and does not address the many faults of hydraulic system itself,It is only a transition product in the development process of hydraulic power steering and electric power steering.It was not until 1988 that Guangyang Company developed an ELECTRIC power steering system with electric power assisted on the steering string. This steering system was assembled on the Cervo model car produced by Suzuki Company of Japan, and the electric power steering system was applied to the passenger car for the first time.In 1990, The Japanese Honda Company also adopted the self-developed rack assisted electric power steering system in the sports car NSX, which opened the history of the application of ELECTRIC power steering in the automobile.

• 1. The purpose and significance of the study

The steering system of a car is a series of devices used to change or maintain the direction in which the car is moving or backing up. The function of the steering system is to control the driving direction according to the driver's wishes. The automobile steering system is very important to the automobile driving safety. It is one of the two systems that must be paid attention to in the automobile safety. Therefore, the parts of the automobile steering system are called security pieces.

Automobile steering systems fall into two categories: mechanical steering and power steering. The mechanical steering system takes the driver's physical strength as the steering energy, and the power steering system USES both the driver's physical strength and the engine (or motor) power as the steering energy. Its emergence and development also has certain process, the first is the traditional mechanical steering system, then on the basis of the research and production of hydraulic power steering system, due to the demand of the market changes, system in updated and improved continuously, the electronically controlled hydraulic power steering system, which implements the electronic control, and with the further research, and has produced the electric power steering system, which is what we call the EPS system.The traditional mechanical steering system is the foundation of the development of the entire steering system. At the beginning, the system mainly relies on human power, which is troublesome to use. Moreover, it cannot play an auxiliary role for the heavy load of the car.Then on the basis of the development of mechanical hydraulic booster and electronically controlled hydraulic power steering system due to solve the problem of the traditional mechanical steering system, widely used in the current car market, but this kind of hydraulic power system need to use the variation of hydraulic power, so the cars need to store large amounts of oil, if car storage system problems lead to oil leakage, damage to the environment not only, and may cause damage to cars and even explode. Electric power this new steering system does not rely on oil pressure to provide steering power, but mainly relies on electricity. Corresponding power supply equipment is installed on the car to drive the motor to provide power for the steering system.Compared with the traditional power steering system, EPS is energy-saving and environmental friendly, easy to install and maintain, and the size of EPS can be adjusted continuously with the change of speed. It has a fast response, which enables drivers to have a good sense of road at all times. EPS is widely used in various automobile brands.

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