ISSN: 2250-3005 - ijcer

Desplacement (m)International Journal Of Computational Engineering Research (ijceronline.com) Vol. 2 Issue. 8Table 1. Quarter car parametersParameters Symbols QuantitiesBody massWheel massStiffness of the bodyStiffness of the wheelStiffness of the damper250 kg50 kg16 kN/m160 kN/m1.5 kN.s/mIII. Input Profile ExcitationThe representation of the road profile is vital for vehicle dynamic simulations because it is the mainsource of excitation. An accurate road model is as important as a good vehicle model. The Excitation input fromthe road is transmitted to the vehicle floor. For the simplification of the dynamic modeling, it is assumed that thereexists only the vertical motion of the vehicle. Both pitching and rolling motions are ignored in this study. Thereduction of forces transmitted to the road by moving vehicles (particularly for heavy vehicles) is also an importantissue responsible for road damage. Heavy vehicle suspensions should be designed accounting also for thisconstraint. In this work, A periodic road excitation input has been used for simulation of suspension systems. Theperiodic input is used for smooth road in order to evaluate ride comfort as shown in Figure 2. It is widelyrecognized that the road surfaces approximate to Gaussian processes, having a power spectral density (PSD) of theform [22]:(3)Where:Road Excitation Frequency, Hz.0.06Randam Road Excitation Input0.040.020-0.02-0.04-0.060 1 2 3 4 5 6Simulation Time (Sec)IV. Robust H Controller (RH )In a typical H ∞ design problem, the nominal plant model represented by its transfer function P(s) is usually known andthe design problem for an output feedback control is formulated as a standard H ∞ problem, as described by the block diagram ofFigure 3. P(s) represents the plant and K(s) the controller transfer function in Laplace domain. The controller is aimed to bedesigned using the H ∞ design technique. In the block diagram, w represents the external disturbances, z the regulated outputsand y the measured outputs. The vector u consists of the controlled inputs[23].Let:Figure 2. Road excitation.P(s) :z1xAx B wC x1y C2D111wx D21Bu2Du12u(4)Controller:||Issn 2250-3005(online)|| ||December||2012 Page 174