| B-double vehicle combination has large load capacity,and it fulfills effective cargo transport with lower cost,so it is more popular used in worldwide.With the sustainable development of social economy in China,wide drop and pull transport in logistics transport will need more types of vehicle combinations.In China,types of vehicle combinations are mainly tractor and semitrailer combination,and the new released Nation Standard(GB 1589-2016)contains central axle trailer for transporting vehicles.B-double vehicle combination(also called B-double),with long body and large load capacity,whose main instability form contains jackknife,drift and rollover form in instability state.It is necessary to analyze the safety of vehicle combination.At present,effects of structural parameter and control system of semitrailer and full trailer type of vehicle combination on handling stability are major object in China.The handling stability and its factors for other types of multi-trailer vehicle combination are focussed on object in the world.Based on these achievements,kinematics models of B-double were developed by means of trigonometric function and geometry principle,and simulation test was given.The B-double model were calibrated and verified.The kinematics model was mainly used to track wheel trajectory of each vehicle unit,and it provided theoretical basis for minimum turning radius and path tracking improvement of vehicle unit in B-double.Based on the classical 2 DOF(degree of freedom)vehicle model in dynamics,semitrailer and B-double model were developed successively.Because the amount of vehicle units increased in B-double,the vehicle combination model would be more complex.Modelling process is tougher and error inevitable.It is necessary to find a method of suitable and efficient modelling.The efficient method provided the general differential equation for multi-trailer vehicle combinations modelling,which improved the efficiency and accuracy for modelling.The combined vehicles of dynamics model mainly presented the lateral motion,the yaw motion and the yaw motion of articulated angle,and in the steady state,the stability factor,understeering parameter,the expression for steady state of yaw rate gain and other steady state of angle gain of each vehicle unit was deduced.The effect of vehicle parameters on those was discussed.To improve the safety and stability of vehicle combination,and to ensure the sideslip angle of each vehicle unit nearly to zero,a method for multi-wheel steering coordination was developed.The rear wheel steering angle of each vehicle unit is proportional to tractor's front wheel steering angle.The steering state was regarded as the desired state of motion for B-double.It could provide a reference for other control model of more complex vehicle.As the test for B-double is in higher risk,based on similarity model test theory,a model vehicle test based on similarity proportional factors was tradeoff configured.The vehicle dynamics state was tested and verified.In summary,the kinematics model of B-double,which is useful for investigating the variety of vehicle parameter's responses on turning radius.The modelling method was used to develop lateral dynamics of multi-trailer vehicle combination efficiently,which is convenient for the analysis of lateral stability itself.The method of multi-axle active steering enhances the safety and stability of each vehicle unit effectively.The simulation test with similarity model theory was effective and provides a concept for test study of B-double or various types of vehicle combinations. |
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