DGIST Scholar: Development of compact steering module and high-fidelity steering feel generating algorithm for steer-by-wire system

Title

Development of compact steering module and high-fidelity steering feel generating algorithm for steer-by-wire system

Alternative Title

SBW시스템을 위한 컴팩트 조향모듈과 견실한 조향감 생성 알고리즘 개발

DGIST Authors

DasolCheon ; Sehoon Oh ; Kanghyun Nam

Advisor

오세훈

Co-Advisor(s)

Kanghyun Nam

Issued Date

2024

Awarded Date

2024-08-01

Citation

DasolCheon. (2024). Development of compact steering module and high-fidelity steering feel generating algorithm for steer-by-wire system. doi: 10.22677/THESIS.200000800158

Type

Thesis

Description

Steer-by-wire system, Steering wheel module, Steering feel, Road environment estimation, Road-Vehicle interaction model

Abstract

This thesis presents research on the development of a compact steering wheel for Steer- by-Wire(SBW) systems and steering feel generation algorithms. SBW is an advanced technol- ogy applied to vehicle systems that eliminates the mechanical connection between the steering wheel and the tire wheels. This characteristic provides distinct advantages and disadvantages for the driver. Detailed advantages and disadvantages are explained in the main body of the thesis. To mitigate the drawbacks and enhance the benefits of SBW, three key issues were addressed from both hardware and software perspectives. During the doctoral course, I developed a novel type of steering wheel module to solve the problem of light mechanical resistance, which is a known issue in steering systems produced by traditional automotive companies. The precision of the steering torque control in the developed module was experimentally validated. Additionally, research was conducted on generating the steering feel, which is one of the critical issues to address in SBW systems. A SBW imple- mentation algorithm was proposed that combines the reference steering model(RSM) method, which allows the driver’s steering feel to be adjusted as desired, with the bilateral control(BiC) method, which conveys road reaction forces to the driver. To quantitatively evaluate the qualitative index of steering feel, a ”Steering Feel Func- tion” model based on transfer functions was introduced. This model allows for quantitative comparison and assessment of the differences between conventional methods and the proposed SBW steering feel implementation method. Furthermore, a method was introduced to define the road-vehicle interaction model using multiple linear regression. This method enables the determination of the restoring stiffness coefficient that varies with vehicle speed. The validity of this approach was verified through both vehicle experiments and simulations. Keywords: Steer-by-wire system, Steering wheel module, Steering feel, Road environment estimation, Road-Vehicle interaction model|본 논문에서는 SBW의 컴팩트 조향휠 개발 그리고 조향감 생성알고리즘에 관한 연구를 제시했다. SBW는 차량시스템에 적용된 최신의 기술로써 조향휠과 타이어휠 사이의 기계적 연결이 끊어진 조향시스템이다. 이러한 특성으로 인해 운전자는 뚜렷한 장단점이 생긴다. 상세한 장단점은 논문의 본문에 설명되고, SBW의 단점을 보완하고 장점을 살리기 위해서 하드웨어와 소프트웨어 관점에서 3가지 문제점을 풀고자 했다

본 연구자는 박사학위동안의 연구를 통해 기존 자동차 회사에서 생산하는 조향시스템의 문제점인 가벼운 기계적 저항문제를 해결하기위한 새로운 타입의 조향휠 모듈을 개발했고, 정밀한 조향토크제어가 가능한 조향모듈임을 실험을 통해 검증했다. 또한 SBW에서 풀어야할 문제들 중 하나인 조향감 생성에 관한 연구를 했다. 운전자의 조향감을 원하는 대로 바꿀수 있는 RSM 방법과 노면의 반력을 운전자에게 전달할 수 있는 BiC방법을 병합하는 새로운 방식의 SBW 구현화 알고리즘을 제안했다. 정성적지표 중 하나인 조향감을 정량적 기준으로 평가하기 위해, 전달함수를 이용해서 정량적 비교를 할 수 있는 "조향감 함수"모델을 제시했다. 이를 이용해 기존방식과 제안하는 SBW 조향감 구현 방식의 차이점을 확인할 수 있었다. 더나아가 도로와 차량간의 상호작용모델을 다중선형회귀모형을 이용해서 정의하는 방법을 소개했다. 이 방법을 통해 차량의 속도에 변화하는 복원력의 강성계수를 찾을 수 있었다. 이는 차량실험과 차량시뮬레이션을 통해 검증되었다.

Table Of Contents

List of Contents
Abstract i
List of Contents ii
List of Tables vi
List of Figures vii
I.Introduction 1
1.1 Research Motivation 1
1.1.1 History of Steering System 1
1.1.2 Steer-by-Wire System 2
1.2 Related Works 4
1.3 Problem Statements 9
1.4 Contribution Points of the Thesis 11
1.5 Thesis Outline 11
1.5.1 Chapter I: Introduction 11
1.5.2 Chapter II: Preliminaries 12
1.5.3 Chapter III: Torque Controllable Compact Steering Wheel Module 13
1.5.4 Chapter IV: Realization of Steer-by-Wire System 13
1.5.5 Chapter V: Road-Vehicle Interaction Model Estimation 14
1.5.6 Chapter VI: Simulation and Experiment 14
1.5.7 Chapter VII: Conclusion and Open Issues 15
– ii –
II.Preliminaries 16
2.1 Analysis of Steer-by-Wire System 16
2.2 Disturbance Observer(DOB) 18
2.3 Internal Model Compensator(IMC) 20
2.4 Steering Feel Evaluation 22
2.5 Series Elastic Actuator(SEA) 25
III.Torque Controllable Compact Steering Wheel Module 27
3.1 Introduction and problem statement 27
3.2 Design of Steering Wheel Module 28
3.2.1 Overall Structure of Developed Module 28
3.2.2 Torque Analysis of Harmonic Drive 30
3.2.3 Dynamic Analysis of Steering Wheel Module 32
3.2.4 System Identification of Developed Module 34
3.3 Precise Torque Control of DOB and IMC 37
3.3.1 Disturbance Observer 38
3.3.2 Internal Model Compensator(IMC) 41
3.4 Chapter Summary 43
IV.Realization Method of Steer-by-Wire System 45
4.1 Introduction and Problem Statement 45
4.2 Steering Feel Evaluation Method 46
4.2.1 Quantitative Index: Steering Feel Function 46
4.3 RSM based Steering Feel Generation 48
4.3.1 Explanation of Block Diagram 48
– iii –
4.3.2 Steering Feel Function of RSM 48
4.4 BiC-based Steering Feel Generation 50
4.4.1 Explanation of Block Diagram 50
4.4.2 Road Reaction Torque Observer 51
4.4.3 Nominal Model for Road Reaction Torque Observer 52
4.4.4 Steering Feel Function of BiC 53
4.5 Reference Steering Model based Bilateral Control Algorithm 54
4.5.1 Explanation of Block Diagram 55
4.5.2 Steering Feel Function of RSM-BiC 55
4.6 Combination Methods of RSM-BiC 57
4.6.1 Simple Gear Ratio based Method 57
4.6.2 Complementary Filter-based Method 58
4.6.3 RSM and Road Vehicle Interaction Model Method 58
4.7 Chapter Summary 58
V.Road-Vehicle Interaction Model 60
5.1 Introduction 60
5.2 Definition of Road Vehicle Interaction Model 60
5.3 Real-time Road Parameter Estimation Method 62
5.3.1 MLR Method 62
5.3.2 RLS Method 64
5.4 Chapter Summary 66
VI.Simulation and Experiment 67
6.1 Experiment for Steering Wheel Module 67
– iv –
6.1.1 Experimental Setup 67
6.1.2 Effect of Low Inherent resistance in Steering Wheel Module 68
6.1.3 Performance Verification of Proposed Module and Control 70
6.1.4 Experimental Verification in HILS 74
6.2 Experiment for Realization of SBW System 76
6.2.1 Specification of SBW Test Vehicle 77
6.2.2 Steering Feel Evaluation 77
6.2.3 Steering Experiment on Constant Road Friction 79
6.2.4 Steering Experiment on Varying Road Condition 81
6.3 Experiment for Road-Vehicle Interaction Model 83
6.3.1 Experimental Setup 83
6.3.2 Experimental Results 84
6.4 Certification of Physical Model of the Road Disturbance 91
6.5 Simulation for Combination Method of RSM-BiC algorithm 94
6.5.1 Simulation Conditions 94
6.5.2 Simulation Results 95
6.6 Chapter Summary 98
VII.Conclusions and Open Issues 101
7.1 Conclusion 101
7.2 Open Issues 102
References 104
– v –

URI

http://hdl.handle.net/20.500.11750/57577
http://dgist.dcollection.net/common/orgView/200000800158

DOI

10.22677/THESIS.200000800158

Degree

Doctor

Department

Department of Robotics and Mechatronics Engineering

Publisher

DGIST

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