Graduation Design (Thesis) of Wuhan University of Technology

Steering System Design of Micro Electric Vehicle

(School): School of International Education

Specialty amp; Class: Automotive Engineering gj1304

Student name: Mei Bo

Tutor: Yu Houyu

Statement of Originality

I solemnly declare that the thesis I submit is a piece of writing I completed independently based on my own research under the guidance of my supervisor. Except for the quotations, this paper does not include any writings published or completed by other individuals or groups. I am fully aware that the legal consequences of this statement are borne by me.

Signature of the author:Mei Bo

Date:2017/5/31

Copyright Letter of Authorization to The Dissertation

The author of this dissertation fully understands provisions stipulated by this school on keeping and using dissertations. The author agrees that the school can reserve and send photocopies and electronic versions of this thesis to relevant departments or institutions managing dissertations. This thesis can be read and borrowed. I hereby authorize excellent provincial institutions appraising bachelor dissertations to incorporate all or any part of this dissertation into relevant databases for retrieval, as well as to preserve and compile this dissertation by photocopying, scanning or reprinting it in a reduced format.

This dissertation is: 1. Confidential until(year) and then this authorization letter will apply. 囗

2. Non-confidential. 囗

Signature of the author: Mei Bo Date 2017/5/31

Signature of the tutor: Date

(Not: this page shall be stapled together with this dissertation as its title page)

Abstract

In this paper,according to the Dongfeng Fengsheng e30l reference model,the steering system of a miniature pure electric vehicle is designed.

The following is the main contents of this paper.

(1) The structural forms of the steering system and its main components are designed,such as the layout of the steering system,the structure of the steering device,the structure of the steering trapezium,the structure of the safety anti injury mechanism,etc.

(2) The major parts are analyzed by finite element method in order to check their stress.

(3)The steering trapezium is optimized by the MATLAB.

(4) In the Adams car simulation platform,a steering system model is established which consists of rack and pinion steering system and Front-Mac Pherson strut,and then the motion of the steering is simulated to judge whether the wheel angle meets the requirements.

(5) To study the control strategy of the steering system.

The results of the study show that the error of Ackerman steering angle and the ideal angle is small,and the ideal angle meets the requirements.The motion simulation of the movement of the steering system shows that there is not motion interference,and wheel angle meets the requirements.

Key words:electric vehicle;electric steering system;steering characteristics;steering power;steering trapezium

Contents

Chapter 1 Introduction 1

1.1 Topic source and research background 1

1.2 Research status of steering system 1

1.2.1 Mechanical steering system 1

1.2.2 Hydraulic power steering system 2

1.2.3 Electric hydraulic power steering system 2

1.2.4 Electric power steering system 2

1.3 Main research contents 4

1.4 Design goals 4

1.5 Research methods 4

1.6 Technical route 5

Chapter 2 Layout Program of Electric Power Steering System 6

2.1 Structure and layout of steering device 6

2.2 Electric power steering mechanism 8

2.2.1 Layout scheme of the electric power steering mechanism 8

2.2.2 Selection of the assisted force curve 9

2.3 Assisted motor 11

2.4 Speed reduction mechanism 11

2.5 Electromagnetic clutch 11

2.6 Control strategy 11

2.7 Safety guards against injuries 12

2.8 Steering universal joint 13

2.9 Steering trapezium structure 14

Chapter 3 Main Performance Parameters 15

3.1 Inside and outside corner and minimum turning radius 15

3.2 Characteristics of transmission ratio 16

3.2.1 Transmission ratio of angle 16

3.2.2 Ratio of force 16

3.3 Transmission efficiency 16

3.4 Steering resistance moment 17

Chapter 4 Calculation of Main Part 18

4.1 Design of rack and pinion steering gear 18

4.1.1 Design of rack and pinion 18

4.1.2 Check the strength of gear shaft 20

4.1.3 Finite element analysis of gear shaft 25

4.1.4 Life calculation of bearings 26

4.1.5 Design and calculation of clearance spring 27

4.2 Selection of power assisted motor 29

4.3 Selection of the electromagnetic clutch 30

4.4 Design and calculation of peed reduction mechanism 31

4.5 Selection of steering wheel type 33

4.6 Design and calculation of elastic coupling 34

Chapter 5 Optimal Design of Steering Trapezium 36

5.1 Steering trapezium model 36

5.2 Relationship between internal and external rotation 36

5.3 Optimal design 38

5.3.1 Objective function 38

5.3.2 Constraint condition 38

5.3.3 Optimized program 38

5.4 Optimization results analysis 38

Chapter 6 Movement Simulation of Steering System 40

Conclusion 42

Reference 43

Appendix 45

Appendix A 45