弯道制动模式下FSAE赛车稳定性研究

Research on Stability of FSAE Racing Car Under Curved Road Braking Mode

为提升方程式赛车弯道制动模式下的整车稳定性,通过实验及有限元方法建立包含发动机外特性,差速机构参数,悬架衬套刚度的整车精确模型;弯道制动工况计算发现整车在制动过程中前轮产生瞬时抱死,后轮产生最大滑移率为0.449的纵向滑移率,整车失去稳定性。针对此问题提出两种改进方案:(1)在前轴双推杆式悬架上增加辅助弹簧与避震器,降低弯道制动过程中前轴垂向载荷产生的侧向偏移;(2)提出弯道制动双模糊控制理论,采用车身横摆角加速度预判直线制动、低速弯道制动、高速弯道制动三种模式所占的权重及对应的模糊控制规则;计算结果表明:方案1使整车在制动过程中前后轴滑移率明显降低,但伴随有瞬时抖动现象,车身横摆角加速度最大值从3.024rad/s^2降低1.741rad/s^2,性能提升42.4%;方案2验证了双模糊控制算法的合理性,使车身横摆角加速度最大值仅为0.509rad/s^2,性能提升83.2%,滑移率变化平稳。

In order to improve the stability of the whole vehicle in the bend braking mode of formula car,An accurate vehicle model including the external characteristics of the engine,the differential mechanism parameters,and the stiffness of suspension bushing was established,mainly through experiments and finite element method.Through the calculation of the simulated bend braking condition,it is found that the front wheel of the whole vehicle generates instantaneous lock,and the rear wheel produces the longitudinal slip rate of 0.449 in the process of braking,the whole vehicle finally loses its stability.Two improvement schemes are proposed for this problem:(1)Add auxiliary spring and shock absorber to the front axle double-push rod suspension,so as to reduce the lateral deviation caused by the vertical load of the front axle in the process of bend braking.(2)According to the curve braking double fuzzy control theory,body transverse angular acceleration,is applied to forecasting the weight and the corresponding fuzzy control rules under the three different modes of the straight line braking,low speed corners brake,high-speed corners brake.The calculation results show that the first scheme can significantly reduce the slip rate of front and rear axles during braking,but it will be accompanied by instantaneous jitter.The maximum acceleration of the body’s yaw Angle was reduced from 3.024rad/s^2 by 1.741rad/s^2,and the performance was increased by 42.4%.The second scheme verifies the advantages of the dual fuzzy control algorithm,which makes the maximum value of the vehicle body’s horizontal pendulum angular acceleration only 0.509rad/s^2,and improves the overall performance by 83.2%.Meanwhile,the slip rate changes more smoothly.