【作者】 刘翔宇；

【导师】 陈无畏；

【作者基本信息】 合肥工业大学 ， 车辆工程， 2010， 博士

【摘要】 随着车辆行驶速度的提高,以及人们对行车安全要求的提高,汽车的安全性成为当前汽车研究中重要的一部分。车辆稳定性控制系统(Vehicle Stability Control,VSC)在制动防抱死系统(Anti-lock Braking System,ABS)、驱动力控制系统(Traction Control System,TCS)的基础上增加了主动横摆控制(Active Yaw Control,AYC)功能。通过方向盘转角传感器和陀螺仪来监测汽车运行参数,并计算驾驶员的期望行车轨迹,在发现汽车有偏离期望行车轨迹的趋势时施加控制,从而避免汽车出现侧向的滑移。不同于传统的被动安全系统,如安全带、保险杠等,VSC作为主动安全装置,旨在危险发生前做出控制,避免事故的发生。由于VSC主要通过纵向力来施加控制车身的侧向运动姿态,因此其控制策略比较复杂,本文以VSC作为研究对象做了以下研究:(1)建立了七自由度整车模型、Dugoff轮胎模型、二自由度半车模型和液压制动系统模型,用于理论研究,在Matlab/simulink中对以上模型进行建模,并对汽车在高低附着路面的运行情况进行了仿真。(2)分析了汽车丧失侧向稳定性的原因,以及横摆角速度和质心侧偏角对汽车稳定性的影响;对直接横摆力矩控制(Direct Yaw-moment Control,DYC)策略的工作原理进行了分析,并采用滑模控制算法设计了控制器和滑移率控制器,最后在Matlab/simulink中进行了仿真。(3)建立了包含侧向风的8自由度整车模型,用于分析侧向风对直接横摆力矩控制的影响,并采用H_∞控制策略设计了抑制侧向风干扰的DYC控制器。(4)提出了采用动态边界来控制质心侧偏角的VSC控制策略。采用车轮侧向力的极限计算质心侧偏角的极限边界;采用横摆角速度增益判断汽车是否处于非线性状态,对处于非线性状态的汽车进行控制,使保持稳定状态。(5)分析了路面对车轮侧偏特性的影响,提出了在转向工况下通过前轮侧偏角估算路面附着系数的方法。设计了扩展卡尔曼滤波器来估算汽车的纵、侧向速度,采用BP神经网络算法设计了路面附着系数估算程序。(6)采用ARM7芯片设计了VSC ECU,基于μC/OS-Ⅱ设计了VSC控制程序,并建立了硬件在环平台,对该ECU进行了测试。更多还原

【Abstract】 With the increased of driving speed and consumers’safety awareness, the safety of vehicles becomes an important research now days. Vehicle stability control (VSC) system is an active safety system, which consists of Anti-lock braking system (ABS), Traction Control System (TCS) and Active Yaw-moment Control system (AYC). A steering wheel angle sensor and a gyro are used to monitor the driving status of vehicle and an expected travel path is confined based on these messages. When it found that, the vehicle has the trend to beyond the expected travel path, VSC will active brake one wheel or two wheels at the same side to retrieve the vehicle to the expected travel path. Different from the passive safety system, such as seat belt and bumper, the active safety system is attend to avoid accident instead of reduce the harm caused by accident. For the available measures of control vehicle’s lateral motion is to change the longitudinal forces, the control strategy of VSC is complex. This paper focuses on the control strategy of VSC, and includes the following contents:(1) The following models: 7 degree of freedom (DOF) vehicle model, 2 DOF vehicle model, Dugoff tire model, hydraulic brake model, are adopted to study the dynamics of VSC. And the vehicle dynamics on both high and low friction road are simulated in Matlab/simulink.(2) Analysised the facts which caught vehicle loss the lateral stability, and the effect of yaw rate an side slip angle to vehicle stability; The Direct Yaw-moment Control strategy (DYC) is introduced, and the sliding mode control algorithm is involved to design the DYC and the slip ratio controller.(3) An 8 DOF vehicle model, includes the interference of lateral wind, is built to analysis the influence of lateral wind on vehicle. To overcome the influence, the nonlinear is adopt to design the DYC controller, and a normol DYC controller based on optimal Control is designed for comparison.(4) The feature of side slip angle and the effect of road friction to VSC are studied; a dynamic boundary method is studied, which has two bounds: the upper bound is defined by the limit lateral forces, and the lower bound is the linear bound of vehicle lateral forces. Based on this control threshold, a nonlinear siliding mode controller is designed.(5) Based on the study of road influence on tire side slip angle, the road friction estimation threshold is designed based on tire side slip angle in steering condition. A extened kalman filter is designed for vehicle’s longitudinal and lateral velocity estimation, and a neural network algorithm is adopted to design the estimation program.(6) The VSC electronic control unit (ECU) is designed based on ARM7, which program is designed inμC/OS-Ⅱsystem. And a VSC hardware-in-the-loop system is built based on labview.更多还原