Study On The Mechanism Of Rollover Instability Of Semi-trailer Train

Now days,semi-trailer vehicles as an essential component of expressway freight vehicles have played a role of increasing significance in road freight transportation system.Yet compare with monomer vehicles,the special connection method and the coupling effect between tractors and semi-trailers resulting in a much more complicated dynamics system.Any vehicular inconsequence of structural parameters,use parameters,and control parameters may possibly bring about the loss of cornering stability and generate folding,drifting even rollover.This paper will focus on the structural parameters,use parameters of semi-trailer trucks in terms of the influences of its cornering yaw and roll stability as a reference to enhance the cornering safety of semi-trailer vehicles.This paper first introduces the main rollover types of semi-trailer in the process of turning,including the rollover caused by turning the direction rapidly,lane change,the emergency braking on the high attaching road;and the low attachment road due to the tractor Skidding,vehicle folding and rollover caused by trailer flick.Secondly,from the structural characteristics of the semi-trailer train and the characteristics of the driver's operation,the causes of the rollover caused by the excessive rollover in the semi-trailer train during the turn are analyzed.Then the theoretical model is used to analyze the mechanism of lateral instability of semi-trailer train in wet-sliding road braking process,which lays the theoretical foundation for the following simulation analysis.Then,access the main parameters of a semi-trailer train according to TruckSim software vehicle modeling ideas,establishing vehicle dynamics model including the steering system,tire system,suspension system,saddle,power train and brake system;establishing straight curve combination road.In the linear range,the five-degree-of-freedom model of the semi-trailer train is used to verify the vehicle model under the step-steering condition.Finally,the simulation process parameters are set up.Firstly,the semi-trailer train is simulated and analyzed in the process of rollover and collapse on the high attaching bend road surface.Taking the lateral transfer of the load as the rollover index,the rolling critical speed of the semi-trailer train model in the steady-state turning of the fixed curve section road is calculated by simulation,and the tractor and the semi-trailer Lateral acceleration threshold.Secondly,through the simulation analysis of the transient rollover process caused by the emergency steering,the lane shifting and the emergency braking,the steering wheel angle of the semi-trailer train with different speed and steering speed is obtained,as well as the different length of the line during the transfer line and lateral displacement of the semi-trailer train to reach the critical point of the rollover speed threshold is also obtained.The semi-trailer train's lateral instability and the road trip caused by wheel lock's different order is also simulated and analyzed in the process of braking in a turn on the low attaching road surface.Finally,the influence of the saddle position,semi-trailer wheelbase and the centre height of the semi-trailer mass on the rollover stability of the semi-trailer train is analyzed,and concluded that reduce the front distance of the saddle,lower the center of mass height and increase the wheelbase can improve the semi-trailer anti-rollover stability significantly.