【作者】 袁朝春；

【导师】 陈翠英； 陈龙；

【作者基本信息】 江苏大学 ， 农业机械化工程， 2007， 博士

【摘要】 电动助力转向(Electric Power Steering System,以后简称EPS)比传统液压助力转向具有节能、环保、结构紧凑及性能优良的优点,成为国内外学者、生产厂家的研究热点。近年来,许多学者在系统建模、助力特性规则、EPS控制原理、控制方法、试验手段等方面进行了卓有成效的研究,取得了大量研究成果,而且,各种类型的EPS产品先后研制出来,其应用范围从最初的微型轿车向大型运输车辆发展,然而,新的课题又摆到了汽车工程师们面前。如在微型车辆上行之有效的助力控制策略应用到重型运输车辆上将不再适应;转向系统在参数摄动和外部干扰的影响下,系统性能降低等等,这些都会给汽车行驶的安全性带来不利影响。为了解决EPS发展过程中出现的新情况,本文从EPS控制基本原理入手,较系统地进行了助力特性规律研究,提出了基于载荷、车辆速度、方向盘转矩的助力电动机理想助力扭矩的特性曲线;利用方向盘转角信号判断驾驶员的操作意图,分析了转向助力控制、回正助力控制、回正阻尼控制的控制原理;针对转向助力过程中存在的参数摄动、外部干扰等不确定性影响,首次提出了用μ控制理论来设计转向助力控制系统,并对μ控制理论设计控制系统的参数摄动线性分式变换理论、外部干扰权函数建模等关键技术进行了深入的研究,在此基础上,设计了EPS试验系统,并进行了台架试验和实车道路试验。首先,分析了影响转向力矩大小的因素,建立了转向力矩动力学模型,结合动力转向系统性能要求和特点,对助力特性进行了较系统研究。提出了新型助力特性曲线,即结合载荷、车辆速度和方向盘转矩三个方面因素确定电动机理想助力扭矩的MVT型助力特性曲线,提高了转向助力效果。其次,在分析电动助力转向系统控制原理的基础上,利用方向盘转角信号和方向盘扭矩信号来判断驾驶员的操作意图。针对驾驶员在转向过程中不同的操作意图提出了转向助力控制策略、回正助力控制策略和回正阻尼控制策略,并给出了阻尼助力线和回正助力线,对回正助力控制和回正阻尼控制给出了数学判定条件;应用自适应模糊PID控制和比例控制策略对回正过程进行综合控制研究。仿真结果表明控制策略效果明显。第三,对于EPS转向系统最基本的转向助力控制,首次提出了用μ控制理论进行系统分析和综合的思路。众所周知,在转向系统动力学建模过程中会存在不同程度的简化和建模误差;在车辆实际运行状况下,模型中的参数会不同程度的改变;转向系统会受到外界干扰力矩的影响;控制器性能会受到传感器噪声的影响,等等。而现代控制理论要求系统模型非常精确,因此模型的参数摄动和外界的各种干扰不可避免的影响EPS控制系统的性能,造成系统性能恶化和不稳定。本文利用μ控制理论分析电动助力转向控制系统动力学模型中的参数摄动、传感器测量噪声、外界干扰(路面倾斜、侧向风)力矩等不利干扰的影响,在求解控制器的过程中应用权函数建模和线性分式变换理论对这些不确定性进行了处理,设计了转向助力过程的μ控制器。μ分析的结果表明该控制器具有更好的鲁棒稳定性和性能鲁棒性。第四,根据新的控制策略,研究开发了以ARM S3C44BOX单片机为微处理器的EPS控制器硬件,控制单元具有实时数据信号采集和系统控制功能,同时采用模块化的设计思想开发了相应的软件程序。将控制硬件与软件进行集成调试,达到了预期效果。第五,创新设计了包含轮胎及悬架结构的新型电动助力转向试验台架系统,用来模拟车速、载荷、结构参数和道路行驶条件对转向系统力矩的影响。在此基础上进行了助力特性曲线台架试验研究、控制器抗干扰试验和回正性能试验研究,试验结果与仿真分析结果基本吻合。表明本文设计的试验装置可以模拟实车行驶条件下转向系统的参数摄动、外界干扰的影响,使试验台架的实际运行效果接近于实车状态,为整个EPS研究提供了良好的试验条件。最后,对装有新设计EPS控制系统的某车型进行了道路试验,并将试验结果与计算进行了对比。研究结果表明,设计的电动助力转向控制系统能够实现对EPS转向系统的性能要求,方向盘转向轻便、回正迅速,并且具有较好的转向手感,特别是,系统具有良好的鲁棒稳定性和性能鲁棒性。更多还原

【Abstract】 Steering system is an important component for ensuring running safety.Compared with hydraulic power steering system(HPS),electric power steering system(EPS)has many excellences.For example,its energy-saving,environment protection,its compact configuration and more excellent performance.So it becomes a hotspot of modem steering system research both at home and abroad.The predecessors have made great progress in modeling the EPS dynamics system,rules of assist torque,control theories for EPS and methods for testing the EPS controllers.In recent years,all kinds of EPS products have been manufactured and equipped on some kinds of micro-vehicles and the super heavy vehicles.Some new problems rise when electric power steering system is used in the super heavy vehicle.This paper does some research on control methods and tests of electric power steering system.First,based on analysis of affection of the assistance character,the model for steering torque of vehicle was built up.The relation between steering torque and load of vehicle was ensured through dynamic simulation and electric power steering test bed. The new assistance character of electric power steering system was built up under the effection of load of vehicle,speed and steering torque.The experiments showed that the character of controller designed under new assistance character was much better.Then,on the basis of analyzing control theories of electric power steering system, the author has made a definition for steering motion.The steering motion has been divided into three basic actions:turn steering wheel,slew steering wheel,retain steering wheel.According to the different intentions,Multi-objects Control Stratagems which based on expert system is put forward.By using logic judgments ability of expert system to judge different steering state for executing control aims which correspond to steering states,the stability of EPS is advanced.At the same time,according to control aim in different steering state,simulation research is preceded.Results show that using this control method can obtain excellent steering ability.Third,Based on the dynamics model of electrical power steering system(EPS),the design of electric power steering control system by usingμanalyses and synthesis is first presented.The effects of high frequency from all kinds of roads and disturbances of sensors noises are considered during designing theμcontroller.Based on the requirement of electric power steering performance and system specifications,the EPS control system architecture and the weighting functions are selected.Theμcontroller of the EPS system was computed through D -K method in Matlab.Simulation shows that the designed controller performs satisfactorily and inherits the imposed robustness and performance sections.Fourth,the hardware that adopted ARM S3C44BOX as its microprocessor is designed.The control unit was able to realize real-time data/signal acquisition and system control.At the same time,the software program,which was divided into the realization of control strategy and the acquisition & control of data/signal,was developed in modular after the circuit design was completed.The last,Based on analyze about abilities of electric power steering system,a new pattern test-bed which contains tire and suspension can reflect steering system more verity.This test-bed can simulate the effects of speed and load of a vehicle and road status.The designing of this test-bed is very usefully to electric power steering system research.This ECU is tested on the test-bed,and the designing way and control strategy in this paper are proved to be feasible.The result indicates that using the proposed ECU of electric power steering system,the steering wheel is easy,and return quickly with good steering feel.更多还原