| In recent years,with the development of domestic tourism,travel trailer has become the main body of tourism transportation.However,due to the complexity of the structure of the travel trailer,the coupling between the tractor and the travel trailer,and the irregularity of the safety evaluation system of the trailer,the matching between the tractor and the travel trailer is often unreasonable,which can easily lead to traffic accidents.As a key factor affecting vehicle driving safety,the travel trailer is more likely to lose its stability when braking than the single vehicle,and even folding and tail flicking accidents may occur under extreme conditions.In this paper,with the help of multi-objective fuzzy control and sliding mode control,the key issues such as braking model establishment,differential braking control,braking moment distribution,and simulation test platform are discussed.First of all,the mathematical model of trailer trailer chassis is established,which consists of electromagnetic brake,tire,flexible hook and suspension.Based on the analysis of the kinematics and dynamics equations of the tractor and travel trailer,the dynamic mechanics model of the travel trailer with load transfer is established.Matlab/Simulink software is used to build the simulation model,and the accuracy of the model is verified by the simulation dynamics software of trucksim.Secondly,in order to ensure that the travel trailer has good yaw stability and driving path under the steering and braking conditions,based on the braking model,considering the yaw rate and articulation angle of the travel trailer as the control objectives,an active differential braking control method is proposed.Among them,the upper controller uses multi-objective fuzzy control to determine the braking torque of the left and right wheels of the travel trailer,and obtains the additional yaw torque of the travel trailer,so as to ensure the good braking stability and driving path of the travel trailer;The lower controller adjusts the left and right brake torque of the travel trailer based on the sliding mode control of the optimal slip rate to prevent the wheels from locking.Finally,Matlab/Simulink and trucksim are used to test the control strategy.Thethree working conditions of steering wheel step,double moving line and fishhook are selected respectively,and the effectiveness of the control strategy is analyzed by combining with the different conditions of high and low road adhesion coefficient.The simulation results show that,compared with the non differential braking,the control strategy proposed in this paper can reduce the yaw rate of travel trailer by about 25%,20% and 30% respectively under three working conditions;Compared with the differential braking control which only takes the yaw rate as the control target,the control strategy proposed in this paper reduces the articulation angle by about 50%,25% and 10% under three conditions.In low adhesion road,the control strategy effectively prevents the wheel from locking.Therefore,the control strategy designed in this paper can effectively improve the yaw stability and path following performance of the travel trailer on the road with different adhesion coefficient. |
