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Autonomous Path Navigation in Citrus Groves Using Machine Vision and Laser Radar
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Paper number 051142, 2005 ASAE Annual Meeting . (doi: 10.13031/2013.19883) @2005
Authors: Vijay Subramanian, Thomas F Burks
Keywords: Autonomous Vehicle, Robotic, Tractor, Machine Vision, Laser Radar, Control, Guidance, Navigation, Citrus Grove
Current navigation systems for agricultural vehicles rely on GPS as the primary sensor for steering
control. In citrus groves, where the tree canopy frequently blocks the satellite signals to the GPS
receiver, an alternative method is required.
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This paper discusses the development of an autonomous steering system for use in a citrus grove.
The vehicle used was a common tractor. The navigation sensor system consisted of machine vision,
laser radar and rotary encoder. Machine vision was used primarily for guidance, while laser radar
can be used for both guidance and obstacle detection. A rotary encoder was used to feedback
steering angle information. A proportional-integral-derivative controller was developed to minimize
the path error. A common PC was used to process the sensor information and execute the control.
The vehicle was tested in flexible test paths constructed of common hay bales. Path tracking
performance was observed. Performance was estimated using RMS error and average
instantaneous error. The guidance system guided the tractor automatically through straight and
curved paths. An average error of 2.8 cm using machine vision guidance and an average error of 2.5
cm using ladar guidance was observed, when the vehicle was tested in a curved path at a speed of
3.1 m/s. The guidance system has successfully guided the vehicle in a citrus grove alleyway.