Biological Systems Engineering


Date of this Version



A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science Major: Agricultural and Biological Systems Engineering Under the Supervision of Professor Roger M. Hoy Lincoln, Nebraska December, 2011

Copyright 2011 Adam B. Flaugh


Power hop is an unstable dynamic phenomenon that is observed on agricultural tractors operating at field working speeds under typical draft loads. This dynamic instability can be identified as a bounce motion preceded by an increasing oscillation in either the pitch or bounce modes. A definite and comprehensive correction or prevention strategy for the control of power hop does not exist. In this work a linear and a nonlinear model of an agricultural tractor were developed. The method of multiple time scales has been employed in the analysis of the nonlinear model. Numerical results have been obtained using Mathematica to verify that power hop can be modeled as a nonlinear oscillator. Solutions to the nonlinear model were obtained for several sets of system parameters. Parametric studies and frequency response curves were performed and investigated.