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Autonomous Agricultural Vehicle Using Overhead Guide

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

Citation:  Pp. 261-269 in Automation Technology for Off-Road Equipment, Proceedings of the July 26-27, 2002 Conference (Chicago, Illinois, USA)  701P0502.(doi:10.13031/2013.10015)
Authors:   B.-S. Shin, S.-H. Kim, J.- U. Park
Keywords:   Autonomous travel, Overhead guide, Tracked vehicle, Steering control

Chemical application is very hazardous work in the confined spaces under the canopy of an orchard. An autonomous guidance system was developed for a track-type agricultural vehicle that could be used in such a working condition. The proposed system could steer the agricultural vehicle by tracking the overhead guide rail, which was installed on the original frame structure. The guidance system consisted of an 80196kc microprocessor, an inclinometer, the interface circuits for actuators for steering operation and ground speed control, and the control algorithm.

Steering along the path was achieved by minimizing the lateral offset the distance between the current location of vehicle, a center point on the front of vehicle, and the desired location on the projected line of the overhead guide rail. This lateral offset was determined by the angle between the imaginary vertical line from the overhead guide rail and the connecting line from the guide rail to the vehicle which is away from the projected line of overhead guide rail. An inclinometer was developed to measure the angle. Overhead guide rails were constructed for the straight path and the curved path simulated the end of the tree row in the orchard.

Evaluation tests showed that the vehicle could travel within an RMS value of 5cm along the desired path and the maximum deviation was 12cm. Even when the vehicle started with the initial offsets or tilted heading angle, the vehicle could move quickly to track the desired path after traveling a certain distance according to the measure of lateral offset or heading angle. On the curved path with the curvature radius of 1m, the vehicle completed its turning securely. However, at high ground speed of 0.5m/sec, the vehicle tended to be over steered, which resulted in the vehicle zigzagged along the straight path and tended to turn outward of the projected line of the overhead guide rail along the curved path.

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