REAR AXLE SUSPENSIONS WITH CONTROLLED DAMPING ON AGRICULTURAL TRACTORS

The main purpose of this work is to study possibilities to improve the vibration damping capacity of a full axle suspension on an agricultur al tractor by various types of controlled damping at the rear axle. In order to perform the study, a full axle suspended tractor has been mo delled and its dynamics simulated in the time domain. The effects of s emi-active damping elements, controlling the dissipation of power with a bandwidth of 50-100 Hz, but not able to add power to the system, ar e studied. The effects of a variant of semi-active damping, needing an electronically controlled actuator bandwidth of only 5-10 Hz, are als o studied. The simulations show that both systems out-perform a passiv e system with fixed damping constants but also that the differences in potential for the two semi-active systems are small. A new type of ad aptive control of the rear axle suspension is also presented, striving to control the damping so that the available travel space is always o ptimally 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 goad characteristics in the simulations.