ROBUST CONTROL OF OSCILLATIONS IN AGRICULTURAL TRACTORS

This paper deals with research results on investigations of robust control of oscillations in off-road vechicles, and relates to analyses and control of the oscillations occurring in many off road vehicles, which are designed without any suspension. Without suspension, the tire is the only elastic element acting between the vehicle and the ground but the suspension and damping properties of the tires cannotmeet the demands for fast, safe and comfortable road transportation.

In this paper, the mentioned phenomenon was undertaken for investigation with special focus on robust oscillations for agricultural tractors equiped with hicth and implements. A control strategy is developed to make the implement counteract the movement of the tractor and thereby reducing the pitching oscillation.

The control strategy is based on a linear plant model with constant or slowly varying parameters. Using a frequency-response approach the disturbance rejection is made effective over a significant portion of the system bandwidth. To improve robustness with respect to bounded disturbances (from the road) natural frequencies for the vehicle and implement is identified and the controller parameters tuned adaptively based on an optimization formulation.