Research On Directional Stability And Control Strategy Of Tractor-semitrailer Steering And Braking

In recent years,with the widely popularizing of Drop and Pull Transport,Tractor-semitrailer has become the subject vehicle of road transport.But the amount oftraffic accident triggered by Tractor-semitrailer has been high level all the time due tothe complexity of body structure|,the imperfection of safety assessing in combinationof vehicles and unreasonable matching in tractor and trailer.Braking stability of the vehicle has been constant attentioned as a problem tosolve. It is easier to lose stabililty than single vehicle when Tractor-semitrailer brakein a high speed transporting, with the reason of road environment complexity and highspeed, especially brake in the corners, which is more easier to produce major accidentof sliding, jackknifing and rolloverring.Therefore, this article focused on the instability mechanism ofTractor-semitrailer steering and braking based on vehicle dynamics theory, whichanalyzed the influence of related parameters on the direction stability whenvehicle braking in a turn, and proposed a control strategy to improve stability ofvehicle steering and braking.Firstly, it was established a chassis system model included braking system,steering system, nonlinear tire, suspension and saddle, and realized the characteristicssimulation of tire model using related parameters. On this basis, developed a18-DOFTractor-semitrailer nonlinear dynamics model considering load transfer invehicle dynamics to describe the motion characteristics of tractor-semitrailer brakingin a turn, and finished the construction of simulation model using byMatlab/Simulink.Built a driving stability detection system of Tractor-semitrailer composed ofgyroscope,VBOX Ⅲ, steering force and angle measuring instrument, brakepedal and brake trigger.Formulated a scheme of Tractor-semitrailer driving circle instability and braking in a turn, and carried out the road test of real vehicle, analyzedthe driving characteristics simulation of vehicle from the test result and calibrated thereliability of simulation model. Meanwhile, simulated and analyzed the effect ofstructure parameters and operation parameters on the direction of Tractor-semitrailersteering and braking, and some improving advice were given from which. At the sametime, with the help of vehicle dynamics theory, theoretically analyzedthe reasons caused by losing stability of vehicle steering and braking, validated thecorrectness of theory analysis from the simulation result output by simulation model constructed.Finally, designed the control strategy according to the mechanism of vehiclelosing stability to improve the stability of Tractor-semitrailer braking in a turn, whichis multi-objective LQR optimal control strategy in lateral acceleration, yaw rate oftractor,jackknifing angle and jackknifing angle rate, Based on the optima control oftire slip rate and the main execution way of differential braking controlling. It wasshown that from the simulation, this active control strategy proposed canimprove the yaw stability and roll stability when Tractor-semitrailer steering andbraking, which can provide technical reference for further development in stabilitycontrol system.