Research On Optimization Of The Tri-axle Semi-trailer Longitudinal-connected Air Suspension For Load-sharing And Ride Comfort

For multi-axle heavy vehicles,favorable dynamic load-sharing ability can reduce peak tire forces,thus preventing overloading of a single axle and alleviating pavement damage.Compared with leaf-spring balanced suspensions and conventional air suspensions,longitudinal-connected air suspensions have been proved to have better dynamic load-sharing performances for multi-axle heavy vehicles.However,the optimization approaches towards the improvement of vehicle comprehensive performances through the geometric design of longitudinal-connected air suspension were considerably lacked.In this respect,a 5-DOF nonlinear model of three-axle semi-trailer with longitudinal air suspension was developed first based on fluid mechanics and thermodynamics.Taking sprung mass and the proper design range of natural frequency of the suspension into account,the longitudinal air suspension height control strategy was proposed with various road roughness,speed and load.Then,in view of the each height of air spring under air suspension height control strategy,the support vector regression method was employed to fit the relationship models between the performance indices and the driving conditions(international roughness index,speed,load),as well as the suspension geometric parameters(inside diameters of the air line and the connectors).Next,based on the interval uncertainty theory,a double-loop multi-objective particle swarm optimization algorithm and a double-loop non-dominated sorting genetic algorithm-II were put forward to optimize the geometric parameters,the Pareto solution frontier for multi-objective optimization at each air spring height was obtained.Finally,technique for order preference by similarity to an ideal solution was used to select the optimal geometric parameters from Pareto solution frontier.The simulation results indicate that compared with the two traditional suspension geometric design parameters in typical conditions,the values of dynamic load sharing coefficient and root mean square acceleration were reduced to different extent.Therefore,the proposed DL-MOPSO algorithm and DL-MOPSO algorithm can improve the comprehensive driving performance of the longitudinal-connected multi-axle truck effectively,and robust to the change of working condition.