外文翻译--牵引力控制系统

附 录 附录 A 外文文献 ELECTRONIC STABILITY PROGRAM Feedback control of the vehicle motion is possible by extending the traction control system with four additional sensors: steering wheel angle,brake pressure, yaw rate and lateral acceleration. Since the nominal trajectory desired by the driver is unknown, the drivers inputs are taken to obtain nominal state variables that describe the intended vehicle motion instead. These inputs are the steering wheel angle, the engine drive torque as derived from the accelerator pedal position and the brake pressure. The handling performance of the car can be improved if in dependence of the steering wheel angle the yaw moment on the car can be controlled.The main task of ESP as an active safety system is, however, to limit the slip angle of the vehicle in order to prevent vehicle spin. ESP can control the yaw moment on the car by controlling the value of the slip at each wheel. This can be shown by the influence of some brake slip value 0 at the left front tire of a free rolling car in a right turn (Fig. 1). )0(FR = is the lateral force on the free rolling tire. Because of the brake slip 0 the lateral force will be reduced to )(F0S where it is assumed, that neither the normal force NF nor the tire slip angle 0 are changed. As a result of the brake slip the brake force )(F0B is generated. )(F0R is the resultant force on the tire, which is the vectorial sum of )(F 0S and )(F 0B . If the tire friction limit is reached, the magnitudes of )0(FR = and )(F 0R are approximately equal. Fig. 1 Yaw moment change by slip control The influence of brake slip is now obvious: a change in the brake slip value results in a rotation of the resultant force on the tire. As a result of the rotation the yaw moment on the car is changed.However, simultaneously the lateral force and thelongitudinal force on the car are influenced. The control concept determines by what amount the slip at each tire shall be changed to generate the required change in the yaw moment. Usually it is required that the driver must not have the impression that with ESP the car is slower than without ESP. The vehicle dynamics controller part of ESP (Fig. 2) constitutes the upper part of a hierarchical control. Output are the nominal tire slips Noi In the lower part the slip values of the tires are controlled. The vehicle dynamics controller part consists of several processing blocks. On the top left the motion desired by the driver is derived from his inputs by a linear bicycle model (which uses a linear relationship between the slip angle and the lateral force of the tire). On the top right the motion of the car is measured and missing state variables are estimated. Fig. 2 Simplified block diagram of the ESP control This estimate is valid if the pitch and roll angles of the car are neglected and furthermore, if the car moves on a horizontal plane. In this equation ya is the lateral acceleration of the car and xa is its longitudinal acceleration, V is its velocity and is its yaw velocity. If the car velocity is constant and its slip angle is small then the estimate can be readily obtained by a simple time integration Offset and other errors in the sensor and estimated signals may quickly lead to large errors in the estimate. Furthermore, during full braking the car deceleration can not be neglected. Therefore,during full braking an alternative estimate of the slip angle based on an observer is used. The observer is based on a full four wheel model of the car and uses two dynamic equations, one for the yaw velocity and the other for the lateral velocity of the car. These equations are rearranged and discretized to be used as the model for a Kalman filter. Since the yaw velocity is measured, the solution of the differential equation of the yaw velocity is used to derive the measurement equation. Here pc denotes a known brake constant, whlp denotes the brake fluid pressure in the brake wheel cylinder, R denotes the known tire radius, CaHalfM denotes half of the engine torque at the axle, whlJ denotes the known moment of inertia of the wheel about its axis of rotation and whlV denotes the wheel speed which is the product of the wheel angular velocity and the tire radius.The engine torque value can be obtained from the engine management system, while the rotational wheel velocity is measured by the wheel speed sensor. Finally by modeling the hydraulic unit the wheel brake pressure is estimated at each wheel. The side forces are not readily available.Therefore a tire model is used. Specifically, the HSRI tire model is used which allows for a simple relation between the lateral and the longitudinal force. The estimate of the lateral velocity by the Kalman filter is robust to tire changes as only the ratio of the lateral and longitudinal tire stiffness is used.For winter tires the ratio is nearly the same as for summer tires. The same is true for new and worn tires, conventional and wide tires etc. Thus both evaluations of the slip angle are more or less insensitive to changes in the tire properties. Unfortunately the vehicle slip angle estimation is not always sufficiently accurate and the confidence level of its value is sometimes low. Therefore, the vehicle dynamics controller uses additionally a model following control for the yaw velocity of the car, for which the already mentioned linear bicycle model is taken. Output of the linear bicycle model is the nominal value of the yaw rate No. Thus a first value for the nominal yaw velocity No is obtained (Fig. 3). The wheel base l is a simple geometric paameter while the vehicle forward velocity xV is estimated by the brake slip controller. Fig. 3 Nominal yaw velocity from the linear bicycle model The characteristic speed chV depends mainly on the lateral tire stiffness C of the tires. Therefore, the nominal yaw velocity changes with the tire type, make and state (new or worn). This change may occur suddenly if new tires are mounted. The model following control is thus sensitive to changes in the tire stiffness and ESP may suddenly change its behavior. This will be shown below. ESP must therefore be checked to correctly perform with all released tires. Since the lateral acceleration of the car can not exceed the maximum coefficient of friction between the tire and the road , the nominal yaw velocity must be limited to a second value by the following relation (see the hyperbola in Fig. 3). VNo g/V For summer tires the nominal yaw velocity is different from that of winter tires (Fig. 4). Similarly,for worn tires the yaw velocity is different from that of new tires. The vehicle becomes oversteer if on the front axle worn and on the rear axle new tires are mounted (Fig. 5). In such cases the vehicle behavior deviates significantly from the behavior of the linear bicycle model (Fig. 3) and ESP interventions can be expected for vehicle maneuvers which are well within the physical limit. Fig. 4 Nominal yaw velocity from the full four wheelmodel with nonlinear new and worn summer and wintertires (steering wheel angle 60) Fig. 5 Nominal yaw velocity from the full four wheel model with nonlinear summer and winter tires, with worn tires at the front axle and new tires at the rear axle(steering wheel angle 60) A first nominal limit value for the slip angle of the car (Fig. 5) is chosen as discussed using the Beta method in dependence of the coefficient of friction between the tires and the road. This value is reduced in dependence of the velocity of the car to a second value No, in order to improve the support for the driver at higher speeds. If the state of the car as described by its yaw velocity and its slip angle differs from its nominal state, then the vehicle dynamics controller checks if this difference is within some tolerable dead zone. If not, a yaw moment is generated to reduce this difference to within this tolerable dead zone. 附录 B 外文文献中文翻译 通过在牵引力控制系统上扩展方向盘转角、制动压力、横摆角速度和侧向加速度四个传感器，就可以实现对车辆运动的反馈控制。 由于驾驶员所希望的名义轨迹是未知的，需要采集驾驶员的输入变量来获得能描述期望车辆运动的名义状态变量。这些输入变量包括方向盘转角、通过加速踏板获得的发动机驱动转矩和制动压力。 如果汽车独立于方向盘转角的横摆运动得到控制，汽车的操纵 性能就会得到提升。然而， ESP 作为主动安全系统，其主要任务是限制车辆的知心侧偏角 来防止车辆侧翻。 图 1 由侧偏角控制引起的横摆运动 ESP 能通过控制每个车轮上的侧偏角的值来控制汽车的横摆运动。在向右转向的自由滚动的汽车上，左前轮的制动侧偏角0的作用可以说明这一点 ，如图 1所示 。 )0(FR = 为作用在自由滚动轮胎上的侧向力。由于制动侧偏角0， 侧向力会减小到假定值 )(F0S，法向力NF和轮胎侧偏角0都不变。由于制动侧偏，车辆产生了制动力 )(F0B。 )(F0R是轮胎上的纵向力，是 )(F0S和 )(F0B的矢量和。如果到达轮胎的摩擦极限， )0(FR = 和 )(F0R的值近似相等。 现在，制动侧偏角 的作用很明显：制动侧偏角的变化会造成轮胎上合力的旋转。由于该旋转，汽车的横摆运动发生变化。但与此同时，汽车上的侧向力和纵向里也会受到影响。控制原理取决于每个轮胎上的侧偏角需要变化多大才能产生期望的横摆运动的变化。通常驾驶员不能有这样的想法：装配有 ESP 的汽车比没装配的要慢。 图 2 ESP 控制的简单框图 ESP 系统的车辆动力学控制器部分组成分层控制的上层部分 ，如图 9 所示 。输出是轮胎侧偏角Noi。在下层部分控制轮胎侧偏角。车辆动力学控制器部分包括一些过程模块。在左上方，驾驶员期望的运动通过现行车辆模型由他的输入得到 (该模型使用车轮侧偏角和侧向力的线性关系 )。在右上方，测量车辆的运动并估计实际的状态变量。 第一种估计车辆侧偏角方法用到侧偏角的导出公式： ）（ s ina-co saV1= xyV+ 如果忽略汽车的前倾角和摇摆角，并且如果汽车在水平面上行驶，这个估计就是合理的。在这个等式中，ya是汽车的侧向加速度 ， xa 是纵向加速度，V是车速， 是横摆角速度。如果车速是常量并且侧偏角较小，可以通过对时间积分很容易地得到估计值。 传感器的补偿和其他误差以及估算信号可能会很快的导致估计中很大的偏差。另外，在全速制动过程中，汽车的减速度不能被忽略。因此，在全速制动过程中，需要用到另外一个基于监测器的侧偏角估计量。 该监测器建立在汽车四轮模型基础上，使用两个等式：一个是横摆角速度，另一个是汽车的侧 向速度。这些等式被重新整理和离散化用作卡尔曼滤波器模型。由于横摆角速度是测量的，该微分方程的解用来推导估计等式。 这些等式中都需要每个轮胎上的纵向加速度 BF ， BF 可以通过下面的等式估算出来。 w h l2w h lC a H a l fw h lpB Vdtd*RJRM-Rp*c=F + 其中，pc指一个已知的制动常数，whlp指的是制动缸内的制动液压力， R 代表已知的轮胎半径，CaHalfM指发动机在车轴上转矩的一半，whlJ指车轮相对于其转动轴线的转动惯量，whlV车轮速度即车轮角速度和轮胎半径的乘积。发动机转矩可以通过发动机管理系统得到，而车轮转速是通过轮速传感器获得的。最后通过液压单元的模型估算每个车轮上的制动压力。 侧向力不是直接就能用的，需要一个轮胎模型。特别地，要用到文献 15中描述的 HSRI