Dynamic performance and ride comfort evaluation of the seat suspension system in a small agricultural tractor to attenuate low-frequency vibration transmission

To obtain safety and ride-comfort conditions for tractor operators, the tractor seat suspension system was analyzed and modified to attenuate the vibration transmission. Experiments were conducted on a standard test track to investigate the effect of seat vibration on operators using a small 4-wheel tractor, and to develop a suitable seat suspension system following ISO guidelines. Dynamic and ergonomic effects of vibration on operator using conventional seat and the new design were compared ensuing standard test procedures. The supportive observations on ergonomic aspects were also made, viz. the operator heart rate, postural comfort survey, and Cornell ergonomic seating evaluation. The vibration of existing seat in vertical direction had the highest amplitude followed by the lateral and longitudinal components sequentially while the new design could significantly reduce the vertical vibration and performed well within the vibration frequencies between 2 to 8 Hz with variable damping constants 1,177.7, 716.5, 695.5, 334.7 and 69.4 ns m^-1, and spring constant of 14,343 N m^-1. The operator could be able to work satisfying 8 h fatigue-decreased proficiency limit, whereas the existing seat's proficiency limit was found slightly below 4 h. Postural comfort and Cornell surveys showed significant improvements in the modified seat transferring it into comfortable zone.