【作者】 宋宇；

【导师】 陈无畏；

【作者基本信息】 合肥工业大学 ， 车辆工程， 2012， 博士

【摘要】 随着对汽车“安全、节能、环保”三大目标越来越高的要求,以及汽车行业越来越激烈的竞争,提高车辆操纵稳定性和安全性的研究受到人们的普遍重视。其中,车辆稳定性控制作为主动底盘控制的重要组成部分,已发展为现代汽车技术的一个重要方向,与已有的四轮转向控制的集成研究也开始受到研究者的重视。四轮转向控制曾经是主动底盘控制的研究热点之一,对于轨迹保持和侧偏角控制有易于实现的优势。然而,四轮转向控制对轮胎侧向力的依赖和轮胎侧向力及侧偏角饱和特性决定了其方法存在较大局限性,目前的发展方向是基于直接横摆力矩控制(Direct Yaw Moment Control,DYC)的车辆稳定性控制。车辆稳定性控制包含两方面的问题,即轨迹保持问题和稳定性问题,分别由车身质心侧偏角和横摆角速度来描述。对于轨迹保持问题,可以车身质心侧偏角为控制目标,对于稳定性问题,可以横摆角速度为控制目标,两者的耦合性也使得车辆稳定性控制算法的研究呈现多元化发展趋势,如横摆角速度控制或质心侧偏角控制或二者的联合控制。由于侧偏角主要是由车辆上的纵向力和侧向力来决定的,用制动力直接控制车辆上的侧向力是比较困难的,而四轮转向系统对轮胎侧向力的控制是直接有效的,因而车辆稳定性控制与四轮转向控制的集成研究具有技术驱动的因素。研究资料表明,以改善高速移线行驶操纵稳定性为主要目标的四轮转向系统通过轮胎侧向力对车辆质心侧偏角控制有易于实现的优势,能够满足一般行驶工况下的稳定性要求；而基于直接横摆力矩的车辆稳定性系统通过调节轮胎纵向力实现了紧急工况下轮胎侧向力趋于饱和状态时车辆丧失稳定性的问题,极限工况下的控制效果较好。于是,将四轮转向系统与车辆稳定性系统相结合,并寻求改善集成系统性能的方法,便成为车辆主动底盘控制新的发展方向。本文以车辆稳定性系统和四轮转向系统的控制研究为基础,探索车辆稳定性系统与四轮转向系统集成控制的方法,主要包括以下内容：建立四轮转向横摆角速度反馈控制系统,考虑到轮胎等非线性因素的影响,同基于神经网络理论的四轮转向控制方法相结合,利用MATLAB神经网络工具箱设计了混合控制系统,实现了四轮转向车辆横摆角速度反馈与神经网络自适应混合控制。对车辆稳定性控制目标进行探讨,对基于直接横摆力矩的车辆稳定性控制逻辑进行分析,设计了一种基于横摆角速度反馈的稳定性控制系统。此系统由四轮制动逻辑控制器和单轮制动PID控制器组成,并同ABS系统的轮胎滑移率控制相结合以防止车轮失稳,解决了当轮胎侧向力接近附着极限或达到饱和状态时,车辆易丧失动力学稳定性的问题。分析了以质心侧偏角为控制目标的四轮转向系统和以横摆角速度为控制目标的车辆稳定性系统的各自特点,将两个子系统结合起来构成集成控制系统。集成控制系统综合利用两者优点,改善路径跟踪性能,提高转向的稳定性,增强高速行驶的灵活性和转向灵敏度,改善瞬态响应品质,使集成控制的综合性能优于单独控制。采用基于ADAMS与MATLAB的联合仿真方法进行计算。ADAMS用于建立系统的虚拟样机模型,MATLAB用于构建分层式集成控制系统。设计了下层子系统控制器和上层系统管理控制器,由上层系统管理控制器对车辆运行状态进行监控和决策。这种分层集成的方式,简化了子系统设计,便于系统扩展,增强了系统的可靠性。通过LabVIEW平台设计车辆稳定性控制实验台进行硬件在环仿真,使用自主开发的控制器进行了台架实验。实验结果表明该系统运行正常,控制效果良好。更多还原

【Abstract】 At present, the study on improving vehicle handling stability and safety is paid attention to by the people with the more and more demands for three goals of aotomobile safety, energy saving, environmental protection and fierce competition increasingly in aotomobile industry. Among them, the vehicle stability control as active chassis technology as an important part of the modern automobile technology has developed into one of the most important direction. The integrated control research with four-wheel steering control also begins to get the attention of researchers.Four-wheel steering control used to be a research hotspot of active chassis technology, and it has the advantage of control system of maintaining track and slip angle easily to be realizd. However, four-wheel steering control exists more limitations because of the dependence of transverse force and the slip angle saturated characteristic, the current development direction is the vehicle stability control technology based on the direct yaw moment control (DYC).The vehicle stability control contains two aspects of the problem, maintaining track and stability problem described by the body slip angle and the yaw velocity respectively. With regard to the problem of maintaining track, body slip can be the control target, and as for the stability problem, yaw velocity can be the control target, the coupling also makes the research of vehicle stability control algorithm present a diversified development trend, such as the yaw velocity control or the body slip angle control or the combined control. Because the vehicle slip angle is determined together by the longitudinal force and the lateral force, it is difficult to control the lateral force directly with the braking force, and the tire lateral force control is direct and effective by the four-wheel steering control, thus the study of vehicle stability system and four-wheel steering system integration has the factor of technology driving.The research data shows that the main goal of four-wheel steering system is to improve the steering stability, and it has the advantage of being easy to realize the goal through the slip angle control by the tire lateral force, and also can satisfy the stability requirements under the general driving condition, and the vehicle stability system based on direct yaw moment solves the loss of stability through the regulation of tire longitudinal force when the tire lateral force tends to be saturated condition under the emergency conditions. So, it becomes a new development direction on the vehicle active chassis control to combine the four-wheel steering system and the stability system and to improve the performance of integrated system.Based on the study of vehicle stability control system, this paper explored the integration control method of stability system and four-wheel steering system, which mainly includes the following content: This paper established the linear2DOF four-wheel steering model and the yaw velocity feedback control system. Further considered the influnence of tires and other nonlinear factors, used the four-wheel steering control method based on the neural network theory, designed the mixed control system using the MATLAB neural network toolbox, realized a mixed control of the four-wheel steering based on the yaw velocity feedback and the adaptive neural network.The vehicle stability control target was discussed, the stability control logic based on direct yawing moment was analysed, a kind of stability control system based on the yaw velocity feedback was designed. This system consisted of a four-wheel brake logic controller and a PID controller of monowheel brake force, and used the ABS system with a tire sliding rate control to prevent wheel instability, solved the loss of dynamic stability when the tire lateral force approached adhesion limit or reached saturation. Each of the shortage was analysed as the body slip angle as the control target for the four-wheel steering system, and as the yaw velocity as the control target for the stability system, and the integrated control system was made up of two subsystem. The integrated control system took advantage of both subsystem synthetically, improved the path tracking performance and the steering stability, enhanced the steering maneuverability and sensitivity, improved the transient response quality and the comprehensive performance of integrated control system.The control system co-simulation was based on ADAMS and MATLAB. ADAMS was used to establish the system virtual prototyping model, considered the requirements of integration control of the stability system and the four-wheel steering system, reserved the integration control interface. MATLAB was used to establish the hierarchical integration control system, designed the lower subsystem controller and the upper system management controller, and the upper system management controller monitored the vehicle running state and decided what to do. This kind of layered integration method improved the vehicle comprehensive performance and ensured that the subsystem has a good performance. The vehicle stability system test platform based on LabVIEW was designed and the simulation of hardware in loop was tested, tested the effect of control strategy, developed the controler based on the rapid control prototype and performed the test bench experiment, the experimental results showed that the system runs normally, the control effect is good.更多还原