Research On Crosswind Stability Of High-speed Vehicles Based On Direct Yaw Moment Control

With the increase of mountainous highways and cross-sea bridges,the crosswind stability of vehicles has gradually attracted people’s attention.An accident may occur if a high-speed vehicle encounters a strong crosswind and the driver doesn’t react in time or overreacts.Therefore,it is of great practical significance to study the crosswind stability control of high-speed vehicles.In this thesis,a two-way coupling method of computational fluid dynamics and multi-body dynamics(CFD-MBD)was proposed for direct yaw moment control of high-speed vehicles.A crosswind stability control strategy based on direct yaw moment control(DYC)by windward front wheel braking was presented.Additionally,a crosswind stability control system based on DYC by multi-wheel braking was also proposed to further improve the control effect.The improvement of crosswind stability of controlled vehicles in open environment and bridge-pylon area was discussed in detail.Firstly,a computational fluid dynamics model was developed and the accuracy of the numerical model was verified by wind tunnel tests.Then,the vehicle multi-body dynamics model was established,and the two-way coupling method of CFD-MBD was proposed.For high-speed vehicles driving in crosswinds,numerical simulations were performed using one-and two-way coupling methods.And the necessity of using the two-way coupling method in the research on the crosswind stability control of highspeed vehicles was analyzed.Secondly,a two-way coupling method of CFD-MBD for direct yaw moment control of high-speed vehicles was proposed.A crosswind stability control strategy based on DYC by windward front wheel braking was designed using fuzzy PID theory.The dynamic response and flow field characteristics of uncontrolled and controlled vehicles under step crosswind were analyzed.Then,in order to further improve the crosswind stability of high-speed vehicles,a crosswind stability control system based on DYC by multi-wheel braking was designed.Additional yaw moment of the high-speed vehicle under crosswind was calculated by the upper controller based on sliding mode theory.This additional yaw moment was distributed to the individual wheels by the lower controller according to a certain strategy.The dynamic response and flow field characteristics of uncontrolled and controlled vehicles under step crosswind were analyzed.Finally,the crosswind stability control of high-speed vehicles passing through the bridge-pylon area was studied.The vehicle aerodynamic model under the bridge-pylon environment was established,and the crosswind stability control system based on DYC by multi-wheel braking was adopted.The dynamic response and flow field characteristics of uncontrolled and controlled vehicles under step crosswind were analyzed.The results show that the yaw angle and lateral displacement of high-speed vehicles under step crosswind are greatly reduced with the involvement of the crosswind stability control system based on DYC.And the crosswind stability of highspeed vehicles can be significantly improved when vehicles pass through the open area or the wake area of the bridge pylon.