A Research On Vehicle Stability Control Method Based On Limited Speed

Vehicle turning stability is an important index to evaluate the performance of the vehicle,which is not only related to the vehicle-self state,but also to the road adhesion coefficient and other external conditions.And vehicle speed often has the most direct relationship to vehicle stability.In the turning process,the high speed often leads to vehicle instability so that can't guarantee the safety of vehicles.In order to improve the vehicle turning stability,the limited turning speed and control strategy was researched.Vehicle dynamics model is the base of vehicle stability analysis.Eight degrees of freedom vehicle lateral dynamics model was established which including vehicle longitudinal motion,lateral motion,yaw motion,roll motion and rotation of the four wheels.The different between the Dugoff tire model and the "magic formula" tire model were contracted and finally the "magic formula" tire model was selected to calculate the tire force.Meanwhile,the engine model,transmission system model and the brake model were established to ensure the integrity of the model.All the models were built in Matlab/Simulink and compared with the CarSim vehicle model which verified the correctness of the dynamic model.Analyzed the vehicle turning limited speed.The vehicle stability was analyzed by using the phase plane method based on the vehicle dynamics model.The difference between sideslip angle-yaw rate phase plane and sideslip angle-sideslip angle velocity phase plane was compared and the sideslip angle-sideslip angle velocity phase plane was chosen to analyze the specific driving state of vehicle stability.It also pointed out the shortcomings of the traditional parallel line method which used to divide phase plane stability region,and the improved double line method combined with the vehicle-self sideslip angle-sideslip angle velocity phase trajectory was used to calculate the vehicle turning limited speed.And then multi simulation experiments were carried out to get the vehicle limit vehicle speed under the full driving conditions.Designed the vehicle stability control strategy and verified with experiments.The limited turning speed was used as the basis to design the engine throttle PID controller.It controlled vehicle stability by controlling the engine throttle opening to change the output torque,and then the engine control limited speed was calculated based on the vehicle track change.Meanwhile,the braking system controller was designed.When the vehicle speed beyond the engine controllable range,a fuzzy controller which used the sideslip angle and yaw rate as input was designed.It calculated the compensate yaw moment to get vehicle stable by applying the braking torque to a single wheel.Finally,the simulation model was established in Simulink,and the driver in the loop experiment was carried out on the simulation driving platform which proved the effectiveness of the control strategy.