Simulation Analysis And Optimization Of Independent Suspension And Vehicle Performances For 8WD Wheeled Off_Road Vehicle

This paper was completed based on the project that "Simulation Analysis and Optimization of Independent Suspension and Vehicle Performances for 8WD Wheeled Off_Road Vehicle"supported by a domestic auto manufacturer. In this paper, by the theory of multi_body system dynamics and virtual prototyping technology, all kinds of three-dimensions solid models and structure specifications of the off_road vehicle were imported into ADAMS software after those were redefined in reason. The virtual prototypes of MacPherson and Single trailing arm independent suspension were created in ADAMS according to spring , damper and bushing characteristics and dealing with the restriction relations and boundary conditions among of parts. The tire and steer system models were established also. Finally, the virtual prototype of full vehicle was assemblied based on all kinds of aforementioned virtual prototype subsystems created. The kinetic motions of the virtual prototypes of independent suspension were simulated and analyzed in ADAMS/Car. Therefore, the changes of wheel alignments that are inclination angle, caster angle, camber angle, toe angle and wheel tack, wheel rate, roll center location, suspension roll rate, tyre slippage angle of Single trailing arm were presented when wheels bumped and rebounded in this paper. The parameters optimization of MacPherson independent suspension was presented in ADAMS/Insight module. The minimum of wheel track change was the objective function of optimal design. The connection measures and hard-point coordinates values of Macpherson independent suspension were the variables of optimal design. Full single factor orthogonal experiments on each design variable were run and analyzed. Therefore, the key design variables that affected wheel track change were finded out, then subordinate design variables were deleted. These were elements for the parameters optimization of Macpherson independent suspension. The analysis result showed that the Z value of the front and rear points of the left and right lower arms, the Z value of the outer points of the left and right lower arms, the Y value of the front and rear points of the left and right lower arms and the Z value of the upper points of the struts were the key design variables. The relation how that key design variables affected the wheel track change were presented through the interaction optimization experiments for the key factors. The connection measures and hard-point coordinates values of Macpherson independent suspension were obtained, which can meet the demands of independent suspension performances. The Driver Control Files for the simulation analyses of controllability and stability of full vehicle were defined based on "GB/T6323.1-94~GB/T6323.6-94 Contorllability and stability test procedure for automobiles". Steady static circular test,Returability test and Steering transient response test were run for the full vehicle model. The simulation results were evaluated and the general score was 94.59 for the full vehicle model based on "GB/T13047-91 Criterion thresholds and evaluation of controllability and stability for automobiles". Through more studying the relation how the torsion stiffness of the transverse stabilizer bar affected the controllability and stability of full vehicle, the reasonable arange of torsion stiffness selected was obtained. The B and E level road models created in ADAMS refered to the road classified criteria in "GB7031-87 Vehicle vibration-Describing method for road surface irregularity"were as the import roads for the simulation and analysis of ride comfort. When the off_road vehicle steered at 75 km/h on B level road model, the curve of third octave spectra acceleration average square roots of the vertical vibration on the seat was under the curve that 2.5hours'tire-efficiency debasement limit within the frequency range of 1~80Hz refered to ISO2631, so the result accorded with the demand of 2.5hours'tire-efficiency debasement limit. And the curve of third octave spectra acceleration average square roots of the horizontal vibration on the seat was under the curve that 8hours'tire-efficiency debasement limit within the frequency range of 1~80Hz, therefore the result accorded with the demand of 8hours'tire-efficiency debasement limit. Based on the above analyses, the driver do not debase work efficiency for vehicle vibration ,but also can still work with well habitus and mentation after the off_road vehicle...