ISSN: 2250-3005 - ijcer

International Journal Of Computational Engineering Research (ijceronline.com) Vol. 2 Issue. 83. Vehicle Model Formulation For Parameters Identification:For simulating the lateral dynamics of the vehicle a four wheel 3 Degree of freedom model is used containing lateralvelocity (V), yaw rate (r) and, roll angle (ϕ).The input of the model is the steering angle on the front tires. Also the continuummass of the vehicle is modelled by three lumped masses which are front and rear unsprung masses (M uf , M ur ) and sprung mass(M s ) so the entire vehicle mass is:M t =M s + M uf +M ur . (1)In order to derive the equation of motion a moving reference frame is attached to the vehicle with its origin at the centre ofgravity as shown in Figure. Since the coordinate system is attached to the vehicle the inertia properties of the v ehicle will remainconstant Also as the result of symmetry assumption all the products of inertia are ignored .The state variables are assumed t o belateral velocity yaw rate and roll angle .Using the above assumptions the equations describing the motion are:, (2)Where:, (3), (4)Where, Ms is the sprung mass, which is the mass supported by the vehicle suspension , ( I xx )is the sprung mass moment ofinertia about longitudinal axis (x), (I zz )is the moment of inertia of the entire vehicle about vertical axis (z), K ϕ and C ϕ are rollstiffness and roll damping coefficient of suspensions respectively ( h s )is the vertical distance of CG from the roll axis, a and bare the distances of the front and rear axles from CG ,u is the longitudinal speed of the vehicle which is constant in vehiclemaneuvers and F yfr , F y fl , F yrr , F yrl are the tire cornering forces of front right front left rear right and rear left respectively.Figure 2 .Vehicle Model||Issn 2250-3005(online)|| ||December|| 2012|||| Page 264