硕士学位毕业论文

硕士研究生：任莎莎

指导教师：沈斌 教授

答辩时间：2012.06

摘要

随着汽车工业的发展，汽车市场竞争日趋激烈，各大汽车生产厂为了争取更多的客户、更大的市场，都围绕改善汽车驾驶的舒适性、节能、环保等方向进行不懈的研究。

汽车电动助力转向(EPS)系统是近年来发展起来的一种新型动力转向系统，具有节能、质量轻、安全、环保等一系列优点，正逐步取代传统的液压助力转向系统，成为动力转向系统发展的一个主流趋势，EPS不仅能够改善汽车驾驶舒适性、节能、环保，同时对降低生产和维护成本、缩短开发周期、减少开发成本等多个方面都大有裨益。因此，发展EPS成为当今汽车生产商、零部件开发商以及科研机构的研究热点。并且随着计算机技术的迅速发展，多体动力学软件MSC.ADAMS的开发，为EPS系统的研究提供了更为方便有效的平台。

本研究着重进行了以下几项工作：

首先，详细分析了EPS的系统结构和工作原理及其主要的组成部件，并分析了EPS转向系统在工作过程中的受力情况,建立了EPS转向系统的动力学方程。

其次，对EPS的关键技术助力特性进行了详细的分析和研究，给出了直线型，折线型和曲线型三种助力特性的数学方程，并分析了三种助力特性的优劣。其后根据曲线型助力特性的数学模型和助力特点，提出了基于BP神经网络优化算法计算任意车速下方向盘转矩与电机助力转矩的非线性关系的方法。对基于BP神经网络优化算法的EPS系统控制策略和算法进行了深入研究,通过分析车辆和驾驶员对转向控制的要求和特点, 获得了汽车车速和方向盘扭矩二输入下的EPS的助力特性。

其后，基于车辆动力学的建模方法, 利用 MSC.ADAMS/CAR 软件建立了EPS转向系统仿真模型,以及用于整车动力学分析的整车模型。

最后，基于ADAMS的整车模型，进行典型工况下的整车仿真分析，通过对有无EPS的横摆角速度和侧向加速度等参数的对比说明了EPS系统对提高汽车操纵稳定性方面有一定的积极作用。

关键词：电动助力转向，助力特性，ADAMS，仿真

ABSTRACT

With the development of the automotive industry, the competition is fiercely in the auto market. In order to get more customers and bigger market, all the vehicle companies are doing their best to improve comfortable of driving, energy saving, environmental protection etc. and direction of unremitting study.

Electric power steering system (EPS) is a new power steering system developed in recent years. With a number of advantages of energy saving, light weight, safety, environmental protection etc., EPS is gradually replacing the traditional hydraulic power steering and has become a major trend in the development of the power steering system. EPS is not only to improve comfortable of driving, decrease consume energy, prevent the pollution of the environment, but also can reduce production and maintenance costs, shorten the development cycles, reduce development costs and other aspects of a great benefits. Therefore, the development of EPS becomes one of the hottest topics what automobile manufacturers, parts developers and research institutions focus on. With the rapid development of computer technology, the multi-body dynamics software of MSC.ADAMS provides a more convenient and effective platform for the study of EPS.

This research focuses on the following aspects:

First of all, a detailed analysis of systematic constructer, the working principle and great compenent, and force analysis of EPS steering system in the course of its work, set up EPS steering system dynamics equation.

Secondly, a detailed analysis and research of power assist characteristic, which is is the key technology of EPS, gave three mathematical equations for a straight line, polyline type and curve type of power assist characteristics, and analyzed the advantages and disadvantages of the three power characteristics. Subsequently, according to curve type of mathematical models and assist characteristics, based on BP neural network, brought forward to calculate the nonlinear relationship between the steering wheel torque and motor power assist torque at any the speed of vehicle. EPS system control strategy and algorithm optimization algorithm based on BP neural network has conducted in-depth research, according to analysis of steering control requirements and characteristics of vehicle and driver, obtained the power assist characteristic of EPS under the two input of the vehicle speed and steering wheel torque.

Secondly, based on vehicle dynamics modeling method, using the software of MSC.ADAMS/CAR, established the EPS system model, and the vehicle model for dynamic simulation analysis.

Finally, based on ADAMS vehicle model, have done the vehicle dynamic simulation analysis under the typical conditions. Compared with the yaw rate and lateral acceleration parameters of vehicle between no EPS and with EPS systems illustrate that EPS have some active role to improve vehicle handling and stability.

Key words: Electric power steering, Power assist characteristic, ADAMS/CAR; Simulation