Rear axle suspensions with controlled damping on agricultural tractors

Abstract

Abstract The main purpose of this work is to study possibilities to improve the vibration damping capacity of a full axle suspension on an agricultural tractor by various types of controlled damping at the rear axle. In order to perform the study, a full axle suspended tractor has been modelled and its dynamics simulated in the time domain. The effects of semi-active damping elements, controlling the dissipation of power with a bandwidth of 50–100 Hz, but not able to add power to the system, are studied. The effects of a variant of semi-active damping, needing an electronically controlled actuator bandwidth of only 5–10 Hz, are also studied. The simulations show that both systems out-perform a passive system with fixed damping constants but also that the differences in potential for the two semi-active systems are small. A new type of adaptive control of the rear axle suspension is also presented, striving to control the damping so that the available travel space is always optimally used, independent of driving speed and ground roughness. The algorithm uses preview information about ground roughness, measured at the front wheel, as a base for the adaptation of the rear suspension, and shows good characteristics in the simulations.