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In this paper a concept of Position-Dependent Damping (PDD) is proposed in which the damping coefficient varies with position and the damper force is a function of both relative velocity and position or relative displacement across the damper. A suitable damping law is proposed for variation of damping coefficient with position for improving performance of passive vehicle suspension. Various parameters are identified for the complete specification of PDD. A new parameter "Energy Dissipation Index" (EDI) is defined for the performance analysis of dampers. The optimum parameters of the damping law are obtained on the basis of EDI. The transient and steady-state response of single DOF vehicle model with linear spring and position dependent damping is analyzed for bump and sinusoidal road input, by performing numerical simulation using MATLAB®. The simulation results show that a properly designed PDD reduces gap between the conflicting requirements the ride comfort and the road holding.

This paper describes the Vehicle Dynamics Modelling and Simulation of a four wheeled ground vehicle. The model so developed and simulated can be integrated with a low-cost PC-based driving simulator that can perform six degree-of-freedom (DOF) motions similar to a road vehicle. The mathematical equations of vehicle dynamics are first derived and incorporated with the tire, steering, brake, engine and suspension subsystems. The mathematical model can accept the inputs from the driver, ground and the environment and generate necessary actuating signals for the motion platform and the visuals of the driving simulator. The model equations have been solved numerically using Runge Kutta -4 method. The model is simulated using Microsoft VC++ 6.0. The iteration time is found to be less than a 0.2 milli seconds making it suitable for integration with a PC based driving simulator.

This paper consists of two parts, modeling of passive sequential strut and modeling of 8-DOF high mobility tracked vehicle incorporating the strut. In first part, a tunable passive, sequential, heavy-duty hydro-pneumatic mono-tube strut is discussed to achieve variable damping for a tracked vehicle suspension. The hydro-pneumatic strut is modeled as a nonlinear dynamical system incorporating nonlinearities due to orifice flow, gas spring and pressure relief mechanisms. The shock and vibration isolation performance of hydro-pneumatic strut are evaluated and compared to the vehicle model employing a constant orifice strut. It is shown that the vehicle ride performance is improved considerably using an adequately tuned sequential hydro-pneumatic strut. In second part, a twelve-road wheel high mobility tracked vehicle, is modeled as an 8 degrees-of-freedom in-plane non-linear dynamic system incorporating bounce and pitch motion of the sprung mass and bounce motion on six road wheels.