Graduation Design（Thesis）of Wuhan University of Technology

The Simulation and Analysis of SUV Handling Stability Based on Matlab

School: School of International Education

Major/Class: Automotive Engineering 1304

Student Name: Yu Jingbo

Mentor Name: Yu Chenguang

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Abstract

In this paper, the 3-DOF simulation model of vehicle handling stability is established based on Simulink module in Matlab，then using this simulation model to simulate the yaw rate, lateral velocity, roll velocity and roll angle of the vehicle when the steering wheel is angle step input, and the change of the tire vertical load during the roll of the vehicle is analyzed. The influence of velocity, tire cornering stiffness, wheelbase, moment of inertia and stiffness of the steering system on the handling stability of the vehicle is also discussed in detail by using the simulation model. Lastly, the paper analyzes the vehicle roll stability from three perspectives which are the driver, the road environment and the vehicle. The research results of this paper have important guiding significance for the study of 3-DOF vehicle handling stability.

Key Words: Matlab/Simulink; 3-DOF simulation model; vehicle handling stability; vehicle roll stability

Contents

Chapter1 Introduction 1

1.1 The research content of this subject 1

1.2 The purpose and significance of the research 2

1.3 Research Status at Home and Abroad 3

Chapter2 Overview 5

2.1 Overview of vehicle handling stability 5

2.2 Evaluation method of vehicle handling stability 5

2.3 Introduction to the driver-vehicle-road closed-loop system 7

Chapter3 Establishment of vehicle dynamics model 10

3.1 Modeling thinking based on Matlab/Simulink 10

3.2 Modeling of vehicle handling model with 3-DOF 10

3.3 Lateral force and side slip angle model of tire 12

3.4 Steering system model 14

3.5 Aligning torque model 14

3.6 Wheel vertical load model 15

3.7 Summary 16

Chapter4 Establishment and analysis of simulation model 17

4.1 The establishment of each subsystem 17

4.1.1 Establishment of tire side slip angle subsystem 17

4.1.2 Establishment of front wheel aligning torque subsystem 18

4.1.3 Establishment of subsystem of steering system 20

4.1.4 Establishment of front wheel vertical load subsystem 21

4.2 Establishment of vehicle simulation model 21

4.3 Basic parameters of vehicle 23

4.3.1 Calculation of roll angular rigidity of suspension 23

4.3.2 Calculation of moment of inertia 24

4.3.3 Determination of other relevant parameters 26

4.4 The calculation of parameters in simulation model 26

4.5 Simulation of steering wheel angle step input of a SUV 29

4.5.1 Algebraic loop in Simulink 30

4.5.2 Simulation results of steering wheel angle step input 31

4.6 Simulation of a SUV under different step angle input 34

4.7 The change of tire vertical load when rolling 38

4.8 Summary 39

Chapter5 Influence of parameters on vehicle handling stability 41

5.1 Influence of driving speed on vehicle handling stability 41

5.2 Influence of tire cornering stiffness on handling stability 43

5.3 Influence of wheelbase on vehicle handling stability 46

5.4 Effect of moments of inertia on the vehicle handling and stability 47

5.5 Influence of steering system stiffness on vehicle handling stability 48

5.6 Summary 49

Chapeter6 Analysis of roll stability based on driver-vehicle-road 50

6.1 The influence of driver 50

6.2 The influence of road and environment 52

6.3 The influence of vehicle 53

6.3.1 Influence of steering system on vehicle roll stability 53

6.3.2 Influence of running system on vehicle roll stability 54

6.3.3 Influence of vehicle structural parameters on roll stability 60

6.4 Summary 61

Chapter7 Summary and prospect 63

References 65

Acknowledgment 66

Chapter1 Introduction

In recent years, vehicle has become a very important tool in our lives, and since the birth of vehicle, the vehicle safety is the focus of engineers to study, In the near future, I believe that the vehicle will be as popular as cell phones. Therefore, it is more important to study the safety of the vehicle. Vehicle handling stability is one of the most important performance of the vehicle, it is a hot issue of automotive safety technology theory, the research and use of ABS and ESP are to improve the handling and stability of the vehicle. With the development of science and technology, especially the continuous development of computer technology, we have been able to use computer software to simulate and analyze the vehicle handling stability, and the simulation results are basically consistent with the experimental results, which provides a great convenience for the study of vehicle handling stability.

1.1 The research content of this subject

This subject is combined with reality, on the basis of a SUV, the three-degree-of-freedom (3-DOF)coordinate model and the dynamic model including lateral motion, yaw movement and body roll motion are established, then according to the vehicle dynamics model, using the Simulink module in Matlab to establish the vehicle simulation model, and the lateral motion, yaw motion and roll motion of the vehicle are analyzed. By analyzing the simulation results, the evaluation indexes of vehicle handling stability such as lateral acceleration, yaw rate, roll velocity and roll angle are obtained, which are used to evaluate vehicle handling stability objectively. And the influence of the cornering stiffness ratio front and rear tire, the roll angular rigidity ratio of the front and rear suspension, steering system stiffness on vehicle handling stability is analyzed.

The basic contents include: