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Development and Validation of Globally Asymptotically Stable Control Laws for Automatic Tractor Guidance

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Applied Engineering in Agriculture. 27(6): 1099-1108. (doi: 10.13031/2013.40613) @2011
Authors:   J. Gomez-Gil, J.-C. Ryu, S. Alonso-Garcia, S. K. Agrawal
Keywords:   Control, Global Positioning System (GPS), Guidance, Agricultural vehicles

Automatic guidance of agricultural vehicles requires the use of sensors and control techniques. While the Global Position System (GPS) is widely used as a position sensor, different control laws have been used in the scientific literature based on geometry, heuristics, and models. In this article, two new control laws for navigation control of agricultural tractors were developed with one for following straight lines and the other for tracking circular arcs. These two controllers have virtually the same structure based on the tractor's kinematic model. They have no singularity point in the state space. Also, global asymptotic stability is guaranteed with the control laws. Guidance with the proposed controllers in straight lines and circular arc trajectories was simulated and field-tested. The experiments were performed with a tractor equipped with an automatic GPS guidance system. In both simulation and experiment, the control laws led the tractor to converge to the desired trajectories of straight lines and circular arc paths under three different low speeds of 1, 2, and 3 m/s and four different initial conditions that are 90 apart. The simulation and experimental results show the practical validity of the proposed controllers.

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