摘 要

EPS（电动助力转向系统）作为一种具有低能耗、低污染以及助力特性可通过电子软件任意改变的转向系统，正在各类车辆上大规模替代传统的HPS（液压助力转向系统）。为了推进EPS广泛多车型应用的进程，本论文旨在为确定车型的微型客车电动助力转向系统设计提供一种详细可行的建议方案。

本论文除去基本的对EPS系统的介绍、系统结构选型、零部件尺寸计算校核等主要设计步骤外，为使设计层面更为多元化，同时对转向系统各部件的设计要求及其可能的优化方案、未来的发展展望进行了不同程度的说明。

相较于发展成熟的HPS,EPS则毫无疑问存在着技术层面较为不足的问题，在其设计方面仍有许多亟待改进之处。现在的主要目标是需要攻克技术难关，在设计出符合现有要求的EPS的同时不断寻求能使系统性能更为优化的可能性，最终打破国外技术壁垒并达到完全国产化。

关键词：电动助力转向系统；微型客车；零部件设计；系统优化。

Abstract

EPS (electric power steering system), as a steering system with low energy consumption, low pollution and assistance characteristics that can be arbitrarily changed through electronic software, is replacing the traditional HPS (hydraulic power steering system) on a large scale in all kinds of vehicles. In order to promote the wide application of EPS for multiple models, this paper aims to provide a detailed and feasible proposal for the design of electric power assisted steering system for micro buses.

In addition to the basic introduction of EPS system, system structure selection, component size calculation and checking and other main design steps, in order to make the design level more diversified, this paper also explains the design requirements of each component of steering system, possible optimization schemes and future development prospects to different degrees.

Compared with the mature HPS,EPS undoubtedly has some technical problems, and there are still a lot of room for improvement in its design. Now the main goal is to overcome the technical difficulties, to design EPS in line with the existing requirements, and to constantly seek the possibility of optimizing the system performance, so as to finally break the foreign technical barriers and achieve full localization.

Key Words：Electric power steering system; Minibuses; Component design; System optimization.

Index

Chapter 1 introduction 1

Chapter 2 The selection of main parameters and the determination of important

parameters 4

Chapter 3 Basic requirements of electric power steering system

14

Chapter 4 General composition and layout scheme of electric power steering system

17

Chapter 5 Electric power steering system components design

22

Chapter 6 Optimization design of steering transmission mechanism

49

Chapter 7 Future prospect of steering system 57

Chapter 8 Conclusions 60

Acknowledgement 60

Reference 61

Chapter 1 introduction

1.1 The introduction

Automobile steering system refers to a series of devices to change or maintain the driving direction or reverse direction according to the driver's will. It is very important to the safety of automobile driving. The performance of steering system is directly related to the safety, handling stability and comfort of the vehicle, and also plays an important role in improving the driving conditions of the driver. Through the continuous in-depth study of the steering system, there has been a change from pure mechanical type to hydraulic power type and then to electric power power type, and its development also reflects people's attention to the steering system from the side. The design of the electric model of the minibus to match the best steering system, so that the vehicle to achieve the best performance for the purpose of continuous optimization.

1.2 Purpose and significance of the topic

The traditional mechanical steering system was quickly eliminated due to its excessive effort and low speed and high speed steering characteristics. Later research and development of hydraulic steering system is listed and is very popular and put into use, after that with the development of hydraulic power steering system for more than half a century, the technology has gradually become mature, with the continuous development of automotive vehicle electronic systems, people demand for auto environmental protection and energy saving has been improved. The inherent deficiency of the steering system, such as high energy consumption and environmental pollution, is becoming more and more obvious. Obviously, the hydraulic power steering system cannot fully meet the requirements of The Times.

In the global development trend of energy conservation and emission reduction, miniaturization and lightweight, the application of ELECTRIC power steering system (EPS) is gradually becoming the mainstream of automobile steering system technology. Especially in the field of new energy and electric passenger cars, EPS can according to the automobile steering torque, steering wheel Angle, speed and road conditions, such as data provides the best steering for the pilot, make a turn to more easily soft, it also can keep the vehicle has good linear ability and the ability to inhibit the bumpy road reaction, ensure the way various driving conditions.

Obvious, to now, the research electric power steering system and related design to improve the vehicle performance is of great significance, this is also for the design of the main objective, namely through the electric power steering system for passenger vehicles related structure selection, finally obtain good performance of steering ability, in order to enhance the vehicle performance.

1.3 Analysis of research status at home and abroad

Since the 1980s, foreign countries began to develop electric steering in cars, and now has achieved considerable results. Lee Junho[1] et al. proposed that the electric steering system could be used to generate auxiliary torque to improve the driver's comfort and realize autonomous steering control without driver torque by using the function of the electric power steering system. In addition, Allous Manel et al. [2] proposed a steering system design concept based on a new fast fault estimation method based on adaptive observer to improve the steering comfort of vehicles by using electric motors. When studying the electric power steering system suitable for the steering characteristics of commercial vehicles, Yaohua Li et al. [3] also analyzed the influence of weight on steering performance and proposed a dual-motor full-weight power steering system. Kazusa Yamamoto et al. [4] studied the cylindrical ELECTRIC power steering system and realized the whole control process of the observer in real time by using dSpace/MicroAutobox. Abolfazl et al. [5] proposed two compromise design points based on the continuous demand for vehicle fuel economy and low exhaust pollution, and compared and discussed them. Faa-jeng Lin et al. [6] proposed an intelligent sliding mode control based on a digital signal processor and applied to the position control of the six-phase PMSM drive system in the power steering system. This series of research results have been widely used in light, mini cars and vans, and are developing at a speed of more than 3 million units per year.

In China, the specific results obtained so far include: in order to adjust the torque according to the speed and other signals and help the driver get the best steering assistance at any time, Yang Lingxiao et al. [7] have designed the method of assisting characteristics by using function calculation and fuzzy control rules. Fang Run [8] proposed series proportional differential control, which effectively accelerated the response speed of the system and improved the stability of the system. In addition, Huang Hanzhou et al. [9] further improved the comfort and intelligence of the vehicle by cooperating with other controllers of the vehicle. Xue Mingchen et al. [10] proposed an EPS current tracking method based on the rolling time domain algorithm. Wang Chao [11] obtained the graph of power characteristic through calculation, which verified the accuracy of power characteristic. Peng Tao et al. [12] proposed an intelligent control method for the motor power control of THE ELECTRIC power steering system. Deng Tian [13] discussed the key technologies of the ELECTRIC power steering system and the overall structure of EPS electronic control part by explaining the operation principle of the ELECTRIC power steering system. Yan Wenjun [14], Yuan Cong [15], Wang Shengda [16] et al. studied the control algorithm and reversion control strategy of EPS system respectively.