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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.
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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.