Analytical and Experimental Studies on Ride Comfort in a Combat Vehicle (CV)

Extremely uncomfortable levels of bounce and pitch vibrations are produced when a CV moves over uneven terrain. The present study was carried out to ascertain the vibrational response at the driver’s, commander’s and trooper’s seats. A 23 -degrees of freedom (DOF) lumped parameter 3-D model of a combined CV and human body was made. The vehicle had 15 DOF corresponding to the bounce, pitch and roll of the hull (sprung mass) and bounce motions of the 12 wheel stations (unsprung masses) on either side. The human body was idealized as having 8 DOF corresponding to bounce motions of the pelvis, abdomen, diaphragm, thorax, torso, back and head. The seat was also assigned a bounce DOF. The lumped masses of the body parts were distributed and connected by springs. The differential equations of motion for the linear rigid body model were formulated and the natural frequencies of different parts of the human body and the military tank were determined by eigenvalue analysis using MATLAB. Subsequently, vertical and longitudinal accelerations at the driver's, commander's and trooper's seats were measured on both the Sinusoidal track and Aberdeen Proving Ground (APG) using accelerometers connected to the DEWESoft data acquisition system (DAS). Fast Fourier transform (FFT) spectra and power spectral densities (PSDs) were determined at each location. Also, the measured root mean square (RMS) accelerations computed in 1/3 octave bands were multiplied with ISO weighting factors and were compared with ISO ride comfort boundaries for assessment of ride comfort. Thereafter, exposure values, A(8) and vibration dose value (VDV) were calculated. A full multi-body dynamics model (MBD) was idealized to get insight into the dynamic behavior of the CV. The vibrational response of the CV was simulated during steady-state runs on Sinusoidal and Aberdeen Proving Ground (APG) tracks through MSC ADAMS (ATV) and the results were compared with those obtained from experimental work. The measured acceleration data correlated well with the computed results.