The current research of real-time observation for vehicle roll steer angle and compliance steer angle(both of them comprehensively referred as the additional steer angle in this paper) mainly employs the linear vehicle dynamic model, in which only the lateral acceleration of vehicle body is considered. The observation accuracy resorting to this method cannot meet the requirements of vehicle real-time stability control, especially under extreme driving conditions. The paper explores the solution resorting to experimental method. Firstly, a multi-body dynamic model of a passenger car is built based on the ADAMS/Car software, whose dynamic accuracy is verified by the same vehicle's roadway test data of steady static circular test. Based on this simulation platform, several influencing factors of additional steer angle under different driving conditions are quantitatively analyzed. Then ε-SVR algorithm is employed to build the additional steer angle prediction model, whose input vectors mainly include the sensor information of standard electronic stability control system(ESC). The method of typical slalom tests and FMVSS 126 tests are adopted to make simulation, train model and test model's generalization performance. The test result shows that the influence of lateral acceleration on additional steer angle is maximal(the magnitude up to 1°), followed by the longitudinal acceleration-deceleration and the road wave amplitude(the magnitude up to 0.3°). Moreover, both the prediction accuracy and the calculation real-time of the model can meet the control requirements of ESC. This research expands the accurate observation methods of the additional steer angle under extreme driving conditions.
轮胎力传感器(Wheel force transducer,WFT)采用串联方式传递地面对轮胎的作用力,增加轮胎质量4～10 kg,此附加质量对WFT本身测量精度和整车稳定性会造成影响。选择8梁和4梁弹性体两种典型电阻应变WFT,对弹性体、未改制轮辋、弹性体+改制轮辋装配体进行模态对比分析。然后量化由轮胎旋转形成的离心力和由弹性体外环垂直运动惯性力形成的附加变形梁拉压变形。基于15自由度整车仿真模型进行90 km/h匀速、160°转向盘角阶跃输入对比试验,根据质心侧偏角和横摆角速度分析WFT附加质量对汽车稳定性的影响。结果表明,弹性体基频振动中变形梁的拉伸和弯曲变形,以及垂直运动惯性力形成的附加变形梁拉压变形是形成WFT系统测试误差的主要因素;WFT安装后会改变整车的稳定性,增加响应延时。
The current research of wheel force transducer(WFT) mainly focuses on test signal processing and decoupling methods based on signal itself, while the WFT structure optimization research related to decreasing the mass and increase the natural frequency and comprehensive sensitivity is not enough. In order to improve the WFT test accuracy, a structure optimization method based on natural frequency and comprehensive sensitivity indicators is put forward. The WFT with 8-beam elastic body is used for the finite element modeling(FEM), in which the following variations are taken into consideration: the connection type of elastic body with modified rim, the number of connection holes, and the respects of strain beam including the shape, the cross sectional area and the length,etc.. The test results shows that the natural frequency of the connecting block type is increased by 65.5% compared with the connecting seat type of elastic body & modified rim, and the main channel sensitivity is improved as well.The results show that the connecting block type will achieve the best comprehensive performance when the number of connecting holes between the elastic body and the modified rim is 20. And the thinner and longer strain beam with smaller cross section area is preferable within the scope of elastic body mechanical strength. This research proposes a novel structure optimization method for WFT which contributes to improve the measurement performance of WFT.
