Simulation Analysis Of Car Air Suspension And Vehicle Performance

This paper was proceeded connecting with the item"The analysis and control of vehicle noise"which is a branch of"863"project presided by NVH group . On the basis of researching elastic characteristics of the air spring, front and rear air suspensions are matched for a certain domestic car.The rate characteristics of the air spring is the most important dynamic feature of the air suspension, it is the base for designing, optimizing, matching and simulating air suspension. But now, we can only get this characteristic by experiments with complicated and high cost equipments. The largest disadvantage of this method is that: the rate characteristics it gets can only act for one particular air spring but not a series. So, as for the designing, optimizing and matching of the air suspension before the air spring have selected, this experimental method can't function at all.In this paper, an air spring rate characteristics experiment is made first, by analysing the experimental data and the theory of air spring, a method to simulate the air spring is made. With this method, the rate characteristics of the air spring can be get by only affording main dynamic and geometry parameters of the air suspension vehicle.The front and rear air suspension multi-body dynamics virtual prototype model is created based on the ADAMS/Car platform. The vertical rate characteristics of the air suspension and original suspension of the car are simulated based on this model, analyzed the different rate characteristics of the air suspension and original suspension. In ADAMS/Car, the full vehicle multi-body dynamics virtual prototype model is created, including the steering system, powertrain system, vehicle body, tires, road, and the above front and rear air suspension.The Driver Control Files for the simulation analyses of controllability and stability of full vehicle were defined based on"GB/T6323.1-94 ~ GB/T 6323.6-94Contorllability and stability test procedure for automobiles". Steady static circular test was run for the full vehicle model. The simulation results were evaluated and the general score of prototype car was 91.88 for the full vehicle model based on"GB/T13047-91 Criterion thresholds and evaluation of controllability and stability for automobiles", and the general score of matching air suspension car was 95.92. This proves that full vehicle of matching air suspension and the prototype car have good controllability and stability.The B 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. On the condition of full-load and idle-load, the cars with two different suspensions runs with uniform speed and straight-line at 70km/h and 120km/h on B level road model, simulation gets the curve of third octave spectra acceleration average square roots of vertical vibration of car-body barycenter were under the curve that 8 hours'tire-efficiency debasement limit within the frequency range of 1~80Hz refered to ISO2631, so the result accorded with the demand of 8 hours'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 cars with two different suspensions steered on the B level road for 8 hours at 70 km/h and 120km/h. But the curve of third octave spectra acceleration average square roots of vertical vibration and horizontal vibration of car-body barycenter with air suspension were under the curve that 8 hours'comfort debasement limit within the frequency range of 1~80Hz refered to ISO2631, so the result accorded with the demand of 8 hours'comfort debasement limit. But when prototype car runs at 70km/h and 120km/h uniform speed and straight-line on B level road model, the vertical vibration acceleration is under the curve of 4 hours'and 2.5 hours'comfort debasement limitation, that meets the demands of 4 hours'and 2.5 hours'comfort performance debasement limitation .However, on the condition of full-load and idle-load, the car of matching air suspension has relatively low simulation weighted acceleration average square roots, and this proves that the ride-comfort of car with air suspension is superior to prototype car and demonstrates it is feasible and meaningful that air suspension is matched on the car.