【作者】 黄晨；

【导师】 陈龙；

【作者基本信息】 江苏大学 ， 车辆工程， 2014， 博士

【摘要】 车辆电控底盘系统是由多个子控制系统组成的,多个可控子系统相互之间影响,车辆综合性能的提高依赖于各个子系统的协同作用。子系统之间协同有利于车辆底盘子系统集成的软硬件共享、能量管理和信息交互,满足车辆安全性、舒适性和经济性的更高要求,实现车辆底盘系统集成化、智能化和网络化,这是当今车辆工程领域学术界研究的热点与难点。国内外科研人员已经在车辆底盘集成控制理论与技术方面开展了大量研究工作,但是一直尚未形成较为完善的理论和体系。转向与悬架作为汽车底盘系统中的两大关键零部件,相对独立而且易于控制,但是如果将他们集成,由于耦合轮胎这一非线性系统,将会使控制变得复杂。本文以转向、悬架以及集成为研究对象,通过定性定量地研究轮胎侧向力与垂向力之间关系,充分发挥轮胎性能对悬架和转向的作用和影响,并进行协同集成控制研究,运用自上而下的顶层设计理念,通过总体规划布局,使子系统之间优势互补,降低或消除子系统之间矛盾和冲突,最大程度减少驾驶意图变化和外界环境影响等引起的车身姿态变化,兼顾并改善行驶平顺性和操纵稳定性。根据这一思路,本文主要围绕着半主动悬架控制、电动助力转向控制和轮胎状态监测以及系统集成控制等方面展开研究工作。建立轮胎侧向力和垂向力耦合神经网络模型。借助轮胎接地压力试验系统进行了多种工况下轮胎侧偏特性试验,分析了侧偏特性与侧偏角、轮速、垂直载荷、充气压力等众多因素关系,选择558个样本,将这些数据点作为网络特征参数,训练和建立自适应神经网络模型,采用了BFGS方法进行参数辨识和网络逼近,通过理论计算验证了可行性,为悬架与转向耦合机理分析奠定理论基础。建立车辆多体动力学模型,其中包括转向、悬架运动学、弹性力学的非线性特性,并进行了模型与实际车辆的对比试验,同时通过台架试验标定半主动悬架中步进电机转角与减振器阻尼力的关系,为半主动悬架控制以及集成控制器的设计提供依据。分析了影响横摆角加速度的因素,采用转向过程稳定性指标,描述车辆在不同车速和路面附着系数下的操稳性问题,并且研究了横摆角速度与侧倾角的非线性关系。通过研究瞬态响应下的性能指标之间的相互关系,分析耦合系统对车辆综合性能的影响。提出了车辆底盘系统协同控制的顶层设计思想,构建了基于模糊关系网协同控制理论的车辆行驶平顺性与操纵稳定性协同机制。根据悬架与转向耦合机理,参考驾驶意图和车辆状态,针对半主动悬架(SAS)和电动助力转向(EPS),按工况进行底盘协同系统的顶层设计,将底盘协同系统分为四个子系统：轮胎子系统(TYPE)、半主动悬架子系统(SAS)、电动助力转向子系统(EPS)和顶层子系统(SYS),在每个子系统之间引入模糊关系型合同网作为协同机制来处理协调和合作的问题,实时地确定子系统模糊权值的比重。运用状态迁移原理建立子系统模块,组成多子系统协调与合作。构建了基于自治体技术的感知、信念、意图统一结构车辆底盘协同系统底层子系统。针对半主动悬架控制系统要求,在平顺性、操稳性和安全性之间进行切换和通信,建立了SAS子系统；针对电动助力转向系统运行过程工况复杂多变、实时性要求较高等特点,建立了EPS多工况切换模糊控制子系统；根据汽车行驶时轮胎力的计算和各种异常情况(如轮胎漏气、过低或过高气压、过高温度)预警的需要,建立了TYRE子系统。搭建了车辆底盘协同控制的联合仿真系统,并进行联合仿真计算。基于多体动力学原理建立系统模型,结合控制器模型,进行了随机路面、蛇行、双纽线和单脉冲角阶跃输入工况的联合仿真计算,对比分析了不同控制方法的仿真结果,检验了控制算法的有效性。设计了车辆底盘协同控制的快速原型半实物仿真系统和台架、道路试验系统。组建dSPACE与硬件连接构成快速原型仿真系统,通过与联合仿真相同工况的计算结果对照分析,验证了快速原型控制器模型的正确性和有效性。基于FlexRay网络对协同底盘系统进行了软硬件设计,同时改进设计了节流口可调式阻尼减振器。在此基础上,自主研发自测量气门嘴替代现有胎压传感器。最后,开发了车辆底盘系统协同控制器,并装车进行道路试验,通过与快速原型控制系统试验进行了比较,验证控制系统的正确性与硬件设计的可靠性。研究结果表明,基于顶层设计的车辆底盘系统协同控制,能够满足不同子系统在不同行驶工况下的控制要求,同时实现多个子系统在协同过程中的协调与合作。与传统分层控制方法相比,在随机路面试验中,车身垂直加速度和前后悬架动挠度均方根值性能指标均得到不同程度改善。在蛇行试验中,转向盘转角平均峰值略有减小,而转向盘转矩平均峰值下降了13.31%,横摆角速度平均峰值增加了9.77%,侧向加速度平均峰值下降了10.01%。在双纽线试验中低附着路面进行转向时,略为减少了操纵转矩,而回正过程中,增加了操纵转矩,考虑驾驶舒适性的同时保证了操稳性。在复合工况试验中,解决了传统分层控制无法避免的车身垂直加速度、车身侧倾角、俯仰角和横摆角速度振动幅值等性能指标很难同时兼顾的局限性。因此,采用顶层设计与协同控制相结合的底盘集成系统,较好地自主协调系统内部资源,减小了矛盾和冲突,在保障子系统功能充分发挥的基础上,很好地实现了底盘复杂大系统全局优化,使车辆操稳性和平顺性得到兼顾,明显提高整车综合性能。更多还原

【Abstract】 Vehicle electronic chassis control system is made up of several sub-control systems, which affect each other and the improvement of vehicle overall performance is dependent on the cooperation of all those sub-control systems. The cooperation of those sub-systems is good for sharing of hardware and software of sub-system integration of vehicle chassis, energy management and information exchange so as meet higher requirements on safety, comfortableness and economy to realize integration, intelligence and networking, therefore, it is the main direction towards development of vehicle technology. Researchers at home and abroad have completed a lot of researches on the vehicle chassis integrated control theory and technology but a sound theory and system are yet to be established from the perspective of methodology.As the two key parts, the steering and suspension are relatively independent and easy to be controlled, but the two are associated with tire, which is the nonlinear system and interconnected with each other. This paper gives a qualitative and quantitative study on the relationship between side force and vertical force of tire to give full play to the impact on and tire performance with the steering and suspension as the subject. In addition, it provides cooperative integrated control study with the use of top-down top-level design concept to reduce or eliminate the conflict among all sub-systems by overall arrangement to complement each other’s advantages of all sub-systems. By thus doing, the variation in vehicle body posture due to change of driving intention and external environmental influence can be optimized to the fullest extent and the driving smoothness and handling stability can be improved at the same time. Based on that train of thought, the paper is mainly developed control of semi-active suspension, electric power steering control and monitoring of tire conditions and system integrated control.The paper establishes a coupled neural network model of side force and vertical force of tire. On the basis of s series of tests on tire cornering characteristics under various operating conditions carried out on the tire ground pressure test bed, the relationship among the cornering characteristics and cornering angle, wheel speed, vertical load and charge pressure etc. is analyzed. And then,588samples are selected and those data points are regarded as network characteristic parameters. After that, a self-adaptive neural network model is trained and established to lay a theoretical foundation for analysis of suspension and steering mechanism with the use of BFGS method for parameter identification and network approximation and by means of comparatively validation with magic formula tire model.The paper also builds a vehicle multi-body dynamics model, including steering and suspension kinematics, non-linear characteristics of elastic mechanics and compares the model with actual vehicle. At the same time, the relationship between stepping motor rotation angle and damping force of shock absorber in the semi-active suspension is determined via bench test so as to provide basis for design of semi-active suspension control and integrated controller.The paper analyzes the factors which affect yaw rate and studies the non-linear relationship between the yaw rate and angle of roll by representing the operating stability of vehicles under different speed and different coefficient of road adhesion as stability index in the steering process. In addition, the impact on overall performance of the vehicle brought about by the coupled system is analyzed on the basis of the study of correlation of performance indexes under transient response. The paper proposes the top-level design concept of vehicle chassis cooperative control and builds the framework of cooperative control of top-down semi-active suspension and electric power steering. It provides a top-level design of chassis system for semi-active suspension (SAS) and electric power steering (EPS) as per the operating conditions according to the coupling mechanism of suspension and steering and with reference to driving intention and vehicle condition and divides the chassis cooperative system into four sub-systems:tire sub-system (TYPE), semi-active suspension sub-system (SAS), electric power steering sub-system (EPS) and top-level sub-system (SYS). The fuzzy relational cooperation network is introduced for each sub-system as the cooperative mechanism to deal with the coordination and cooperation so as to determine the percentage of fuzzy weight of each sub-system in real time.A unified bottom sub-system based on perception, conviction and intention is designed. Considering the requirements of semi-active suspension control system, switch and communication between the smoothness, operating stability and safety is realized, a SAS sub-system is established and design of damping shock absorber with adjustable throttling mouth is improved; due to complicate and changeable working conditions with high real-time demand during operation of the electric power steering, the EPS sub-system is established to realize fuzzy control of switch of multi-conditions; the TYRE sub-system is established in light of the requirement of calculation of force of tires during driving and alarming of various abnormalities (such as tire leakage, under-pressure and over-pressure and over-temperature) and inflating valve provided with automatic pressure measurement developed independently to replace the current tire pressure sensor. A test bed including tire, suspension and steering and a simulation system are designed. Several joint simulation tests under step-input conditions such as random road, pylon course slalom test, lemniscate test and monopulse angle are made based on the system model established in accordance with principles of multi-body dynamics and in combination of controller model. After the tests, the results under different control method are compared and analyzed to check the validity of control algorithm. A rapid prototype simulation system composed of dSPACE and hardware connections is set up to verify the correctness and effectiveness of controllers by comparison with results of the joint stimulation tests under same working conditions.Hardware and software design of cooperative chassis system is made on the basis of FlexRay network and the damping shock absorber with adjustable throttling mouth are improved and inflating valves provided with automatic pressure measurement to replace the current tire pressure sensors are developed independently. Finally, the cooperative controller of vehicle chassis system is developed and tested after installing on the vehicle and the correctness control system and reliability of hardware design is verified by comparison with test results of the rapid prototype control system.The results show that the cooperative control of vehicle chassis system based on top design could meet the requirements of different subsystems under various driving conditions. Meanwhile, the cooperation and coordination of multi-systems during the cooperative process is also achieved. Compared with the traditional hierarchical control, the RMS values of the body vertical acceleration and the dynamic deflection of the front and rear suspension is improved to different degrees in the experiment with random road excitations. In the pylon course slalom test, though the average peak value of steering wheel angle is reduced slightly, the average peak value of steering wheel torque is reduced by13.31%, and the average peak value of yaw velocity is increased by9.77%.The average peak value of lateral acceleration is also reduced by10.01%. In the lemniscate test, when the steering is performed on low adhesion road, the handling torque is decreased slightly. However, during the aligning process, the handling torque is increased. Both ride comfort and handing performance is ensured. In the complex conditions test, the proposed controller effectively solves the limitation of taking many performance indicators into account, such as the body vertical acceleration, body roll angle, body pitch angle and yaw velocity, etc, which can’t be avoided by traditional hierarchical control. Therefore, the integrated chassis system with combining the top-level design and collaborative control can autonomous coordinate the system internal resources and attenuate the contradictions and conflicts between different subsystems, which achieve the global optimization of complex chassis system based on guaranteeing the full exertion of subsystem functions. The proposed chassis system gives consideration to both the vehicle handling stability and ride comfort and significantly improved the comprehensive performance of the vehicle.更多还原