Sujatha C., Ravi Shankar M.

Tracked vehicles such as earthmoving and military vehicles, designed for mobility over rough terrain impose a severe ride environment to occupants and onboard instrumentation due to the magnitude of ride vibrations arising from dynamic terrain-vehicle interactions. Ride vibrations transmitted to the driver’s compartment are of high amplitude and low frequency, the conditions to which the human body is most fatigue sensitive. Prolonged exposure to such vibrations causes the operator bodily discomfort, physiological damage and reduces performance efficiency and thus the mobility performance of the vehicle is limited. In this paper, ride dynamics of a tracked vehicle has been evaluated for different terrain at constant running speeds. For this, a simplified linear in-plane mathematical ride model of a typical tracked vehicle formulated as a “2+N” degrees of freedom (DOF) system is used. The vehicle is assumed to traverse an arbitrary, but specified terrain at constant speed. The N bounce modes of the N road wheels on each side constitute N degrees of freedom and the remaining 2 degrees of freedom correspond to the bounce and pitch modes of the centre of gravity (C.G) of the hull. A non-linear model of the hydrogas suspension system has been used. The track is assumed to be a massless continuous belt. The hydrogas suspension is characterized from the load-deflection data for different gas pressures and is constrained to translate in the vertical direction. The equations of motion for the vehicle are derived using Newton’s laws of motion and natural frequencies are determined by eigenvalue analysis using MATLAB software. The vehicle responses to different terrain (cross country, sinusoidal and APG) are obtained by solving the equations numerically using the input data of road profiles. These results have also been compared with those obtained using a linear model of the suspension.