| In recent years,the frequent occurrence of traffic accidents,including the accidents caused by braking problems among heavy trucks,has brought great hazards to society.Therefore,the braking performance of heavy trucks turns out to be particularly significant and it's essential to check it regularly to ensure the safety of the vehicle.So far,the equipment for testing the braking performance of multi-axis vehicles has been a roller-type braking test bench with loading function.The current national standard stipulates that the test bench should reach the lifting height of 100 mm when testing.However,in the actual test,the lifting height cannot meet the demand that all multi-axis vehicles reach the full load,resulting in errors in the test results.Aiming at the problem,therefore,the lifting-type loading braking test system is studied in this paper.On the basis of a large number of domestic and foreign references,the paper has explained the principle and process about how the braking test system operates.By establishing and analyzing the mathematical model of the wheel braking force,it is determined that the axis load of vehicles is the main factor influencing the braking force.So,the paper focuses on the relationship between lifting height and axis load.To support the simulation work,it is used that to build the mathematical model of elastic suspension system and load distribution of multiaxis vehicles and to derive axis load formula when multi-axis vehicle is under no-load and fullload conditions.The multi-axis vehicle types were studied and the target vehicle types were determined respectively.The vehicle-test bench physical model was built using SolidWorks.ADAMS was used to carry out simulation.With the simulation data analyzed and processed,the liner relationship between lifting height and axis load,as well as the formula,was determined.Based on the formula,the lifting height,from no-load to full-load,was calculated.To verify the accuracy of the lifting height,ten four-front-wheels-ten-rear-wheels heavy trucks were selected as the test objects for vehicle test.The lifting load brake test system is introduced in detail from three aspects of technical parameters,hydraulic system and electric control system.Two test projects named a and b were carried out.After the analysis and process of the vehicle test data,making sure the actual relationship between lifting height and axis load and comparing it to the simulating one,the reliability of simulation results is verified.By lifting the vehicle to the target height,the actual axis load was obtained and compared it to the target one,the accuracy of lifting height is determined.This paper draws the following conclusions:(1)The axle load produced by different vehicles being lifted to the same height is different.There is an error in the load braking force detected under the current standard.(2)The no-load multi-axle vehicle can reach the full-load axle load through lift loading.When lifting a four-axle vehicle,the second and third axle load increases linearly with increasing lift,and the second axle can more easily reach the axle load at full load.(3)The lifting height of different no-load vehicles required for lifting to full load is different.The same lifting height can be referenced between different vehicles of the same brand model.This paper can provide reference for the detection of multi-axis vehicles,which has certain practical significance. |
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