Simulation And Evaluation Of Vibration Performance For Multi-axis Heavy-duty Special Automobile Under Different Road Models

Road roughness is the main source of automotive vibration, and automotive vibrationaffects various performances of automobile. When driving actually, automobileencounters complex road conditions. The current research on the road is mostlybased on the standard level road, little on non-standard roads such as rural road,and field road et al, that makes the research on the road incomprehensive. Toimprove the theoretical research of the road model and to lay the foundation of roadfor the research of automotive performance, it is necessary to analyze different roadmodels.As the platform of load transportation, detection, erectness and launch, multi-axisheavy-duty special automobile travels on a variety of complex roads including slough,sand or snow et al, and vibration of multi-axis heavy-duty special automobile iscaused inevitably. The vibration affects not only the accuracy of combat, but alsoreliability of load.Currently, there are few researches on vibration performance of multi-axisheavy-duty special automobile, expect for simulation of model with few degrees offreedom in the frequency domain under random road and there is no evaluationresearch. Therefore, it is necessary to simulate and evaluate the vibrationperformance of multi-axis heavy-duty special automobile under different roadmodels.The purpose of this article is to provide basis for improving the vibration performanceof multi-axis heavy-duty special automobile through simulation and evaluation underdifferent road models. The main contents are:（1）Study of road roughness frequency domain model The standard form of road roughness frequency domain model was described, themodified form was given because of inadequacies of theory, and the spatial lowercut-off frequency of modified form was determined. The four common rational formswere described uniformly, the parameters of rational forms were determined inaccordance with modified form. The uniform expression of power spectral density ofthe soft road was established and the parameters were summarized. The time powerspectral density expression of hard road was summarized, the irrationality of unevengravel was discovered, and modified through conversion of the time and spatialfrequency. The simulation of soft road and hard road were respectively comparedwith the standard form, and special road other than the standard form were elected.（2）Study of road excitation time domain modelThe four kinds of triangle progression form simulating road random excitation wereidentified by introducing four kinds of triangular progression form simulatingstationary normal stochastic process. Standard form of road was simulated andverified using four kinds of triangular progression form, the results show that thefourth form has higher simulation accuracy. The modified form, four rational formsand special form were simulated with the application of the fourth form.The triangular bump and semicircular bump of pulse excitation were described. Themodels of road pulse excitation when single-axle automobile driving for two kinds ofbumps were established and simulated according to the respective applicationconditions.（3）Vibration modeling of multi-axis heavy-duty special automobile with fifteendegree-of-freedom in plane systemAccording to the actual arrangement, the mechanical model of multi-axis heavy-dutyspecial automobile with fifteen degree-of-freedom in plane system was establishedbased on certain assumptions. The mathematical model expressed in matrix formwas determined according to the Lagrange equation. The expressions of wheel staticload, conventional vibration response and special vibration response of multi-axisheavy-duty special automobile were determined.（4）Simulation and evaluation of vibration performance for multi-axis heavy-duty special automobileThe simulation methods in frequency-domain and time-domain for vibrationperformance of multi-axis automobile in plane system were studied and commonexpressions were established. Frequency response characteristics of vibrationresponse of multi-axis heavy-duty special automobile were derived, and evaluationmethods for vibration performance of multi-axis heavy-duty special automobile weregiven. The simulations of multi-axis heavy-duty special automobile infrequency-domain and time-domain were carried out under random excitation andsimulation results were compared. The simulations of multi-axis heavy-duty specialautomobile under triangular bump and semicircular bump were carried out. Thecorresponding absorbed power, human weighted acceleration root mean squarevalue and maximum acceleration of human body were obtained based on thirteenkinds of random roads and two kinds of pulse roads, and beneficial results providingbasis for improving the vibration performance of multi-axis heavy-duty specialautomobile were obtained.