AMT车辆弯道行驶换挡策略

Self-adaptive curve gear-shifting strategy for automatic transmission vehicles

针对使用普通换挡规律车辆在过弯道时易出现降速时升挡、不能及时降挡等问题,研究利用预知弯道半径、车辆距弯道距离信息的弯道换挡策略.该策略根据弯道行驶目标,提出2个弯道换挡指标:保证车辆操纵稳定性的侧向加速度安全阈值ays和人体可容忍侧向加速度阀值aypot.通过车辆行驶动力学分析及过弯观测实验发现,ays、aypot不是常数而是随车辆速度、弯道半径而变化.利用车辆过弯观测实验数据建立ays、aypot与车辆速度、弯道半径间的数学关系.使用降挡提前系数kj将ays、aypot指标应用到换挡策略中对过弯降挡速度进行修正.采用Matlab/Simulink建模针对3种初始速度的过弯工况对上述弯道换挡策略进行仿真验证,并在试验场利用实车进行过弯实验,结果证明所提出的弯道策略能够消除弯道意外换挡并能根据行驶工况及时换挡.

A gear shifting strategy using information of bend radius and distance of the vehicle to the curve was proposed in order to solve the problems of unexpected shift and untimely downshift for automatic transmission vehicles in cornering driving.Based on the requirements of security and physiology,two gear shifting indexes were built:the lateral acceleration safety threshold,which ensured vehicle operation stability,and the lateral acceleration threshold that driver could tolerate.The vehicle dynamics analysis and the observation of vehicle cornering experiment indicated that the lateral acceleration safety threshold and the lateral acceleration threshold were not constant but varied with vehicle speed and turning radius.The mathematical relation between vehicle speed,turning radius and gear shifting indexes was established,according to the observation data of vehicle cornering experiment.The two indexes were applied to gear shifting strategy by downshift time coefficient which corrected the cornering downshift speed.The gear shifting strategy was analyzed with Matlab/Simulink simulation model at three different initial velocities,and the effect of the strategy was verified with vehicle cornering experiment in proving ground.Results showed that the unexpected gear shifting and untimely gear shifting were eliminated with the application of the strategy.