Research On Rollover Warning And Anti-rollover Control Of The Tractor Semitrailer

In recent years,with the increase of highway network coverage,the road transportation industry has been greatly developed.Tractor semitrailer has become the main force of road freight because of their large cargo capacity and good transportation economy.Due to heavy weight,large volume,high center of mass and the force and motion interference between tractor and trailer,tractor semitrailer is not only complicted to operate,but also instability phenomenon is easy to appear at high speed,such as shimmy,tail flick and rollover,leads to heavy traffic accident.For these reason,a six-axle tractor semitrailer is selected as the research object,this paper focus on three aspects: vehicle modeling,rollover warning and anti-rollover control,the main research contents and conclusions are as follows:(1)Research on the yaw-roll dynamics model of six-axle tractor semitrailer.Firstly,consider the sideslip movement of tracor,the yaw and roll movement of tractor and trailer,five degree of freedom yaw-roll dynamic model is established.Then,with the help of single lane change and double lane change,the accuracy of the model is verified based on the dynamic response out of the vehicle model in Trucksim.Finally,in oeder to obtain related parameters in real time,a method for eatimating the state of tractor semitrailer is proposed,the effectiveness of the proposed state estimation method under given conditions is verified.(2)Research on rollover warning of semitrailer.First of all,the traditional rollover index is discussed.The lateral load transfer rate(LTR)is analyzed based on the simplified model and the dynamic rollover index for tractor semitrailer is obtained.Secondly,the threshold of the dynamic rollover indexs are selected by analyzing the vehicle rollover situation under different conditions.Then a rollover warning algorithm is built based on the 5-DOF dynamic model,the status of the tractor and semitrailer is updated in real time,then the rollover warning time is obtained;Finally,verifying the rollover warining system through single lane change and double lane change,the results show that rollover warning algorithm based on dynamic rollover index can realize the advance warning to the driver before vehicle rollover.(3)Research on differential braking control of tractor semitrailer based on LQR.In order to achieve effective anti-rollover control for tractor semitrailer,firstly,a differential braking control strategy is proposed.The goal is to eliminate the deviation between actual and ideal sideslip angle and yaw rate of tractor and trailer,the LQR controller is designed to control the vehicle actual state track the ideal state,the additional yaw moment is generated by applying braking force to the wheel.Then,the weight coefficient of the LQR controller is optimized based on genetic algorithm.Finally,the simulation tests are carried out under lane change and double lane change,the feasibility of the proposed differential braking control strategy and the effectiveness of the designed LQR controller are verified.(4)Research on differential braking control of semitrailer based on MPC.Considering the high speed nonlinear effect of semitrailer,the linear simplified model will enter into the nonlinear region during actual driving,the MPC controller has good real-time performance,strong robustness,and can reduce the bad effects of low model accuracy and the interference of uncertain environment.Therefore,the MPC controller is designed based on the differential braking control strategy.The controller uses the expected value of the 5-DOF dynamic model to correct and control the stability of the vehicle The simulation results show that the proposed MPC controller can effectively prevent the vehicle from instability.