| Multi-axle heavy duty off-road vehicle (MHDOV) is usually used as transportation andlaunch chassis of weapon system. Its characteristics directly influence the performance of thetransportation and projection of weapon system. Therefore taking research and develop withMHDOV to satisfy the requirement of mobile launching of strategic weapon is verynecessary. MHDOV have multi axles, long wheelbases and heavy duty. Its structure anddynamic characteristics are more complex than the ordinary two axle vehicle. However,nowadays at home there is not having the whole vehicle dynamics model that is special forMHDOV. That restricts the dynamics research of MHDOV and it is the important reason thathas caused the notable gap of design level of MHDOV between china and developedcountries. Compared with the two axle vehicle the dynamic characteristics of MHDOV have twodifferent features: (1) the frame flexibility of MHDOV has notable influence on vehicledynamics; (2) the multi-axle steering technology is applied in order to increase themaneuverability of MHDOV. Aiming to these features in this dissertation the whole vehicledynamics modeling theory and method of MHDOV are studied, the correspond simulationsand tests are performed, and the main contributions of the research include: (1) The frame of MHDOV is thought as an elastic body. The vehicle flexible dynamicsmodel of MHDOV is present based the dynamics of flexible multibody System, and theinfluence factors are analyzed. The transform methods among the vehicle flexible dynamicsmodel, rigid model, ride comfort model and handling model are discussed in detail. Thepresented flexible dynamics model has good versatility because it does not consider thespecific elastic mode shape of frame and the axle number of MHDOV. (2) According to the obtainable parameters information at different design stage, amethod using elastic beam to simulate the frame mode shape of MHDOV is proposed, and anhalf vehicle ride comfort model which is suitable at conceptual design stage of MHDOV. Thehalf vehicle model can be used to analyze and evaluate the ride comfort of MHDOV that onlyneed a few necessary feature design parameters. A whole vehicle ride comfort model which isusing frame FEM mode analysis results is also presented. The road random excitationgenerating algorithm in time domain is proposed by using trigonometric series, and the roadexcitation model of MHDOV in time domain and frequency domain are built. The ride IIIcomfort simulation results show that the elastic vibration of frame of MHDOV is theimportant factor that influences the ride comfort and must be considered in MHDOV design. (3) A flexible 2DOF (two degree of freedom) steering model of MHDOV is proposed,and the frame rotation angle calculated method is derived by using three moments equation.According to stability theory of ordinary differential equation the steering stability criterionof MHDOV is obtained, and the influence of frame flexibility is analyzed. Then the steeringperformances of MHDOV with different multi-axle steering mode are simulated with theWS2500 five axles vehicle as investigated subject. A control strategy with steering anglescaled to the first axle steering angle adding yaw rate feed back control is presented. Thestrategy effectively improves the steering stability of MHDOV with keeping the mobility atthe same time. (4) Combined with preview optimal curvature diver model the closed loop steeringmodel of MHDOV is modeled. In order to fully reflect the steering ability of MHDOV, a newassessment index considering road follow up error and track deviation between the firstwheel and last wheel simultaneity is proposed, and the simulation is performed. At last the ride comfort test of the WS2500 five axles vehicle is carried out. Thecomparison between test and simulation shows that the frame flexibility is the importantfactor that influences the dynamic characteri...
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