Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Agricultural and Biosystems Engineering


Low frequency terrain-induced tractor vibration levels exceed proposed International Standards Organization fatigue-decreased proficiency limits. A suspension system is needed to protect the operator and attenuate the vibration inputs to the chassis and the operator platform for "high speed farming systems". Computer simulation modelling of the suspension system provides information for the design and about its performance;The first section of the dissertation discussed the design considerations for off-road vehicle operator ride comfort, the means to improve ride comfort, and computer simulation techniques to evaluate ride comfort;The second section presented a matrix-computer procedure for the vibrational analysis of articulated planar and spatial mechanisms. The procedure computed the frequency-domain transfer function ratio sets for the equations of motion for the mechanical system having "small" oscillatory steady-state motion about its static equilibrium position. This procedure was incorporated into the generalized mechanical systems simulation program, Integrated Mechanisms Program (IMP). A post-processor program was developed to use the transfer function ratio sets computed by IMP and to compute the response of system design variables in both the frequency- and time-domains, the magnitude and phase angle responses in the frequency-domain, and the vibrational mode shapes of the system;The third section discussed the development of a chassis suspension system. Twenty-four tractor, 24 tractor-plow, and 18 tractor-trailer models were developed to evaluate the effect of a suspension system and its parameters, and the influence of the position of the operator cab on ride comfort. The IMP and post-processor programs were used to simulate the dynamic response of these models. The study found: (a) the chassis system reduced the vibrational levels imposed on the tractor operator when compared to unsuspended tractors; (b) the position of the operator cab affected the ride comfort; (c) the tractor-trailer models had the highest levels of vibration when compared to the tractor and tractor-plow models.



Digital Repository @ Iowa State University,

Copyright Owner

Paul William Claar, II



Proquest ID


File Format


File Size

405 pages