Study On Stability Control Strategy Of Tractorsemitrailer Based On Parameter Identification

Tractor-semitrailer has become the main compoment of road freight system because of high transportation efficiency,good fuel economy and low operation cost.However,tractor-semitrailer also has high center of gravity,large weight and volume,complex dynamic system causing by coupling of tractor and trailer,its security risks are also high.Based on previous research work,this paper focuses on the safety of tractor-semitrailer,deeply analyzes the yaw stability and roll stability control of tractor-semitrailer,and proposed an integrated yaw and roll stability control strategy.The work done is as follows:（1）The establishment of actual vehicle model and theoretical vehicle model of tractor semitrailer.A tractor-semitrailer model representing the actual vehicle is established in Trucksim,and the three-degree-of-freedom yaw model and five-degree-of-freedom yaw-roll model of the tractor-semitrailer are built in Matlab/Simulink to calculate the ideal state.Then,the accuracy of the theoretical model is verified by simulation.（2）Parameter identification of theoretical model and online estimation of state parameters.The genetic algorithm is used to identify vehicle parameters that cannot be directly obtained in the theoretical model,including cornering stiffness of the front and rear axles of the tractor and semi-trailer axle6)₁、6)₂、6)₃,the roll stiffness of the tractor and semi-trailer6)₁、6)₂,the roll damping of the tractor and semi-trailer(8₁、(8₂.The extended Kalman filter algorithm is used to estimate the vehicle parameters such as the position of the semi-trailer’s center of mass and the moment of inertia that change with the load of the semi-trailer on-line,and the center-of-mass slip angle and vehicle roll angle that cannot be directly obtained in the test are replaced with filtered observations.The accuracy of the established theoretical model is verified by comparison with Trucksim simulation results,and an accurate theoretical reference model is established for the subsequent stability control strategy.（3）Establishment of stability control strategy and verification of control effect by simulation.The reason and mechanism of the instability of the tractor semi-trailer are analyzed,and the judgment index of the instability is determined.According to the control strategy of the differential braking,the fuzzy PID controller is first established.The deviation and the deviation change rate of the yaw rate based on the Truckism value and the theoretical model value determine the required additional yaw moment,and then the additional yaw moment is reasonably distributed to each wheel,and the slip rate of the semi-trailer train is controlled by the logic threshold control method.Finally,the designed control strategy was verified by Matlab/Simunk-Trucksim under the conditions of steering wheel angular step and double line shifting.