Development and application of VPG simulation technique based on equivalent virtual road profile

Abstract

NOMENCLATUREx(n), X(f )= input vectors in time and frequency domain y(n), Y(f )=output vectors in time and frequency domain G ( ) = auto(xx) and cross(xy) power spectrum H( ) = frequency response function ∆ = sampling period [sec] Ω = frequency resolution [Hz] ( )* = complex conjugate of ( ) ( ) + = pseudo-inverse of ( ) ( ) T = transpose of ( ) ( ) (i) = iteration index DFT{} = discrete Fourier transform IDFT{} = inverse discrete Fourier transform A Virtual Proving Ground (VPG) is a vehicle simulation environment used for evaluating durability of the suspension elements. Among the components that comprise the VPG system, the tire model with its complex nonlinear characteristics has most significant impact on the credibility of the estimated durability. This research proposes a method for generating an equivalent road profile as a way to compensate for the limits involved in modeling details of the tire characteristics. The method first identifies the frequency response function from the road heights to the spindle forces, which would contain rich information on the tire's effect on the vehicle dynamics. Then it back-calculates a road profile using this model and the spindle force measurement. Finally the solution is updated iteratively until it yields the spindle forces close to their measured values. Using the proposed method, an equivalent road profile was successfully generated from a spindle force measurement collected from a physical durability test. In order to investigate validity of the proposed method, durability analysis was performed for a suspension component -a lower control arm. From the preliminary VPG simulation results, it was confirmed that the estimated fatigue life agreed well with the estimation based upon the force measurement.

Application of Multibody Simulation for Fatigue Life Estimation

“…For accurate fatigue life estimation, loads should be applied in three dimensions, making it close to the loads that the part encounters in the real world situation. Multi Body Simulation (MBS) is a good technique to calculate the load time history on the connection points of the knuckle on the suspension system (Kamal et al, 2012;Kang et al, 2010). In this paper, fatigue life estimation has been performed using the load time history calculated from MBS using a MBS software package, in which an actual gravel road profile at 60 km/hr, with standard SAE load distributions (SAEBRAKT, SAESUS and SAETRN) are considered as the input loading (Socie and Artwohl, 1978).…”

Study Effects of Vehicle Velocity on a Road Surface Roughness Simulation

“…Attempts by various organizations have been made over the years to classify the roughness of road surfaces. The International Organization for Standardization (ISO) has proposed a road roughness classification (classes A-H) based on the power spectral density [4,5]. Figure .3 shows the classification proposed by ISO.…”

Lightweight Design of Commercial Vehicle Cab Based on Fatigue Durability

“…This simulation method, also known as Virtual Proving Ground (VPG), can provide necessary data for vehicle structure development and part design, thus reducing the risk and cost in the later verification. To give full play to VPG technology advantages, Kang et al [7] got the transfer function of the whole vehicle model under road excitation by calculating the axle head force, and the road excitation spectrum was obtained by iterating through designed algorithms. Then, the obtained spectrum is imported into VPG for whole-vehicle simulation analysis, to make up for the error of fatigue analysis result caused by the lack of tire modeling accuracy.…”