【作者】 李欣；

【导师】 陈杰；

【作者基本信息】 上海交通大学 ， 车辆工程， 2009， 博士

【摘要】 随着电动助力转向(Electric Power Steering,简称EPS)系统越来越被广泛应用在轿车上,人们对EPS系统的操纵性能要求也越来越高,这给EPS系统控制器的设计提出了极大的挑战。本论文针对EPS系统在汽车转向与回正工况下的各项操纵性能要求及其影响因素,设计一种内外环双层结构的控制器。所设计的控制器首先在EPS系统模型中进行仿真分析,然后进行软硬件实现,并在台架和实车试验中对仿真结果进行验证,从而证明本文设计的控制器能够有效提高EPS系统的操纵性能。主要的研究内容和成果概括如下:一、建立了EPS系统的动力学模型和简化的两自由度汽车模型。通过分析EPS系统原始动态性能,提出系统中存在的不确定因素,并详细分析了不确定因素对操纵性能造成的影响。针对EPS系统的各项操纵性能要求,设计一种内外环双层结构的控制器,包括主环路控制和伺服环路控制。针对汽车在行驶过程中的转向和回正工况,主环路控制分为转向控制策略和回正控制策略。二、在主环路转向控制策略中,提出了一种由分段多项式确定助力特性曲线的方法,此方法确定的助力特性曲线能够为驾驶员提供比较好的“手感”,但同时也为EPS系统带来了非线性因素。为了实现EPS系统在不确定干扰因素影响下的转向操纵性能,设计了保证EPS系统时滞相关鲁棒镇定的H∞鲁棒模糊状态反馈控制器。仿真结果表明,所提出的转向控制策略能够保证转向过程中的操纵性能要求:提高转向轻便性和“路感”,改善转向跟随性和转向力矩平顺性,使系统具有鲁棒稳定性。三、在主环路回正控制策略中,为了克服转向系统的参数摄动、外界干扰以及非线性摩擦,采用基于参考模型的滑模控制算法实现EPS系统的回正控制,并设计滑模观测器观测不可直接测量的状态量。仿真结果表明,所提出的回正控制策略不仅能够实现EPS系统在汽车低速时的回正性能,而且能够提高汽车高速时的操纵稳定性。四、提出EPS系统伺服环路控制策略的设计方法。针对助力电机存在的两大扰动因素:摩擦和外部干扰,采用基于干扰观测器的PID控制算法。仿真结果表明,所提出的伺服环路控制器对于干扰起到了很好的抑制作用,目标电流的跟踪性能得到很大的改善。五、从硬件和软件上设计EPS系统双层结构控制器。设计开发EPS系统的试验台架,进行转向轻便性和转向跟随性的操纵性能试验。将EPS样机安装在某型号的轿车上进行转向和回正性能实车试验,试验结果验证了所建立的EPS及两自由度汽车模型及参数的正确性,进一步证明本文提出的控制策略能够实现EPS系统操纵性能要求。本文针对EPS系统的操纵性能要求及其不确定影响因素,研究、设计并实现一种双层结构控制器。通过仿真及试验,验证了本文所提出的内外环双层结构控制器较传统的单层结构PID控制器,更能满足EPS系统的操纵性能要求,具有一定的理论价值和实用价值。更多还原

【Abstract】 With the increasing number of EPS systems installed in vehicles, people pay more attention to the handling performance of the EPS system, which challenges designing such controller with high performance.In this paper, a two-lay structure controller is proposed to improve handling performances in the steering and returning process with uncertain influencing factors. Simulations for the study of the controller have been carried out in the EPS model and verified in the experiments of test bench and vehicle. The content and results are summarized as follows.Firstly, EPS dynamics and simplified vehicle model are established to analysis the influencing factors. This paper developed a two-lay structure controller with main and servo loops to improve the handling performance of EPS system. The main loop consists of steering assist control strategy and return control strategy according to the driving conditions.Secondly, in the steering assist control strategy, a new method to define boost curve in form of piecewise multinomial is proposed, which can provide a good“steering feel”to the driver. However, the boost curve is also a nonlinear factor to the EPS system. In this paper, a time delay-dependent H∞robust fuzzy state feedback controller is adopted to achieve the handling performances in the steering process. Simulation results show that the steering assist control strategy proposed in this paper can achieve the handling performances in the steering process, including steering easiness and road feel, tracking performance, steering smoothness and robust stability.Thirdly, in the return control strategy, a sliding mode controller based on a reference model is adopted to deal with the parameters uncertainty, external disturbance and nonlinear frictions. A sliding mode observer is developed to estimate the immeasurable states. Simulation results show that the return control strategy proposed in this paper can achieve fast and accurate return with low vehicle speed and handling stability of the vehicle with high speed.Fourthly, a PID controller with disturbance observer designed in servo loop to weaken the effect of the frictions and disturbance. Simulation results show that the proposed controller in servo loop can suppress the disturbance well and the tracking performance to the target current is improved.Lastly, a two-lay structure controller with the proposed control strategies is development, including the hardware and software. A test bench is established to debug the controller. Experiments for steering easiness and tracking performance are carried out in the test bench. An EPS system is assembled with the designed controller and installed in a car. Steering and returnability maneuver experiments are carried out in the car. Experimental results validate the EPS system and vehicle models and prove that the proposed control strategies can get better handling performance.In this paper, a two-lay structure controller is studied and realized to achieve the handling performances of EPS system with uncertain influencing factors. Simulations and experiments have been carried out and show that the control strategies proposed in this paper could meet the requirement of the handling performances better than that of the traditional one-lay structure PID controller.更多还原