Vehicle Suspension Rigid-flexible Coupled Modeling And Whole Vehicle Performance Analysis & Improvement

The performance of chassis is directly determinant factor which decides the important index of a vehicle controlling such as the handling characteristic,riding characteristic, breaking characteristic, etc, The design and improvement of chassis system therefore have been a key technology in vehicle design, and the characteristic of suspension K&C which is considered as the soul of the chassis designing in the function of chassis is more important. By means of analysing the the effect of suspension hardpoint and the scattering of bushing stiffness to suspension K&C, and the effect of suspension K&C to the function of ertire vechicle, constituting relation between the scatter of suspension hardpoint and bushing stiffness and the performance of vehicle have a important directive action in the designing and improvement of vehicle.The thesis combining with a project named "improving the capability of independent innovational of chinese high technology Automobile, make use of virtual prototyping technology to build the dynamical simulated model prototype prior to producing the actual physical sample, and estimates, simulates its handling characteristic of controlling and inclination of tyre wear under the condition of running along the straight line, and optimizes the performance of vehicle according to the analysis the impact of suspension hardpoint and bushing stiffness on the function of entire vehicle.Surrounding this , this thesis have mainly accomplished the following studing content:Firstly by means of analysing the the topology structure of the foresuspension and backsuspension in prototype car, considering the flexibile component in the suspension system, the stable axis of foresuspension and backsuspension bearing the force and force moment from strenching, turning back, curving, etc, and the fact what will complicated deformation is flexible component, backsuspension longitudinal arm has important impact on the K&C characteristic of suspension. For the accuracy of analysis, making the suspension model produced approaching reality more, writer make use of finite element software Hypermesh and Patran to simulated analyse the fore and back stable pole and back-longitudinal arm, generate Adams inputable modal Neutral File, build the rigid-flexible coupled model of foresuspension and backsuspension. This thesis also make elastic kinematics simulation to the foresuspension and backsuspension, analyse the change tendency of wheel allocation index which will be affected by the vertical force , side-force, cross force, qualitative analyse the impact of the change of the prototype car's wheel allocation index on handling characteristic of entire vehicle. All of this will lay down a basis for the improvement of successive work.Secondly , on the basis of foresuspension and backsuspension model, writer want to build a structure-oriented entire car simulated model of prototype including the bodywork, powertrain system, braking system, steering system, tire,and make use of the model to carry out many international stability simulation, analyse appraise and compare the comment standard of showing the handling characteristic which stem from processing the simulated conclusion and the guiding maximum value of handling characteristic and the maximum minimum value of comment standard stipulated in the method of appraising with the result aimed at bid vehicle reality test. Among them, the comment standard of Steering wheel angle pulse input, Returnability test, Steady static circular test, Pylon course slalom test almost be the same to bid vehicle,almost reached the target of design, but the result of Steering wheel angle step input is poor, and have shown obvious lagging reaction.For the progrom of entire vehicle change lagging reaction, by means of carrying out theoretical analysis about the changing transient reaction of vehicle, we can ascertain the equivalence side-deviation stiffness of fore axis and insufficient Vergence degree as the sensitive factor which will affect the transient reaction. For the vergence degree of entire vehicle is in fairly good level, we can make sure of the scheme that we can elevate the equivalence side-deviation stiffness of fore axis and back axis, with basing on the premise that we do not change vergence degree, and analyse the key factor which affect the equivalent side-deviation stiffness when the hung rack side-direction force toe changes. By means of formula inference and analysis by the force, we can analyse the effect due to the impact of the hardpoint allocation and the stiffness allocation of rubber bushing on the characteristic of suspension side-direction toe, and raise a scheme of adjusting about bushing stiffness, make a transient respondent test on adjusted vehicle. The result shows that change veering transient responding is accelerated obviously;Then, put the prototype vehicle in a simulated test of straight line running under the three different condition, kerb,mean,gvw, and forecast the tendency of tyre abrasion in according to the value of side direction force when the vehicle run along straight line. It is hoped that tyre side direction force moving straight under three kinds loading state is increasingly small increasingly well. we can find that the tyre side direction force is bigger when the vehicle move straightly under the loading state of kerb and gvw, and improve the matching relation of toe and camber which will affect the tyre's side direction force under different loading state, and this will reduce the side direction force under various loading state,dimish the targer of reducing the inclination of tyre abrasion.Finally,make use of the finite element software to found four kinds of longitudinal arm flexible model which have different stiffness, take extra loading simulated test on different longitudinal arm hung model, then get the quantify relation of the impact of changing of longitudinal arm stiffness on suspension C characteristic, make use of four kinds of longitudinal arm to carry out a turning angle step test on the back suspension of rigid-flexible coupled model, then analyse the impact of longitudinal arm stiffness on the turning characteristic of vehicle, lay down a basis for the improvement of suspension and the adjustment of prototype.