This paper presents a novel application of a model reference adaptive control (MRAC) system to control the lateral position of a farm tractor tracking a straight path. Farm tractors can be configured with various implements, and the tractor yaw rate dynamics vary with each implement. It is desired that the lateral position response of the farm tractor remain consistent with respect to different implement configurations. Therefore, a MRAC system is implemented on the farm tractor to compensate for yaw rate plant variations by adapting the feed-forward yaw rate controller. Simulation results of the algorithm are shown that display poor performance due to neglected steering actuator dynamics and saturation. Modifications are made to the algorithm to account for the steering actuator properties, and more simulated results are presented that display ideal performance. Finally, the MRAC algorithm is implemented on a John Deere 8420 farm tractor, and experimental results are presented. C 2009 Wiley Periodicals, Inc.
This paper presents a model-reference adaptive controller (MRAC) for steering a farm tractor with varying hitch forces. Hitch forces play an important role in the yaw dynamics of the tractor, and these forces change with respect to different implements and soil conditions. It is desired that the tractor has the same dynamic response no matter what the hitch forces may be. A good dynamic yaw model has been developed for a tractor with hitch forces, and one parameter in this model changes with hitch loading. A MRAC algorithm is consequently proposed to directly adapt one controller parameter to changing hitch loading. A set of cascaded controllers will be used to regulate the tractor's lateral position, although only the controller that directly regulates the yaw rate will be adapted. The adaptation algorithm is then augmented to account for innerloop steering actuator dynamics and saturations. Simulated and experimental results are presented.
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