No 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.

Methods have been developed to reduce the side load and friction force acting on the shock absorber inherent in the MacPherson strut system, popularly used in vehicle suspension systems. Reducing this friction force is one of the most important issues in improving the ride comfort of a car. The side load of the shock absorber can be reduced by controlling the force line of the coil spring. To reduce the side load, we designed an S-shaped coil spring. For the design of the side load spring, we also developed an analytical process, which utilizes finite element analysis and mechanical system analysis. All analysis results for the stiffness, stress, fatigue life, and spring force line were validated through experiments.