Research On Cornering Braking Stability And Hardware-in-Loop Simulation Of Three-axle Vehicles

Automotive Anti-lock Braking System(ABS)and Electronic Stability Program(ESP)have been a hot spot of vehicle active safety researches.The integration of both has become an inevitable trend in the development of automotive brake control.Though effective coordination,the braking distance can be shorten,and at the same time the vehicle's directional stability can be increased.The research of coordinated control on both in the complex braking conditions is important to improve automotive active safety.Three-axle heavy vehicles have considerably lower maximum deceleration than passenger cars and take 40% more distance for emergency stops on dry road surfaces.In order to improve the handling stability and shorten the braking distance of three-axle vehicle under straight line braking and turning braking conditions,three kinds of ABS controllers are designed respectively.The control effects of three kinds of controllers under straight line braking conditions are compared clearly and in great detail.On this basis,an DYC/ABS coordinated control strategy is proposed.According to the parameters of the real vehicle,the whole vehicle model is established in TruckSim.Two kinds of ABS sliding mode controllers are designed by using saturation function and improved exponential approaching rate law respectively,aiming at reducing the flutter phenomenon caused by conventional sliding mode control structure.A dynamic fitting method of tire cornering stiffness is proposed to modify the linear two-degree-of-freedom vehicle model.A direct yaw moment control controller is designed by model predictive control method.Based on Dugoff tire model,the relationship between compensation yaw moment and wheel slip rate is established,and the control boundary value of wheel slip rate is calculated.Through the co-simulation of TruckSim and MATLAB,the vehicle response while braking under different speed and turning radius is analyzed.Because of the big wheelbase,heavy load,large deviation of configuration parameters,and low production in single batch of heavy trucks,developing and matching of DYC/ABS coordinated control by field tests are usually costly and have high risks.Hence,the inevitable trend is to search for a method combining the configurable HIL equipment and system model so as to develop the control algorithms and calibrate the control thresholds rapidly and conveniently.A HIL test system for heavy trucks with pneumatic brake system is built to further validate the effectiveness and real-time performance of the proposed control scheme.The simulation and test results show that the proposed coordinated control strategy can improve vehicle stability,reduce lateral acceleration,braking distance and braking time under different speeds and turning conditions.