Automatic Steering of Farm Vehicles Using GPS

Automatic Steering of Farm Vehicles Using GPS

Abstract

Operating agricultural equipment accurately can be difficult, tedious, or even hazardous. Automatic control offers many potential advantages over human control; however, previous efforts to automate agricultural vehicles have been unsuccessful due to sensor limitations. With the recent development of Carrier Phase Differential GPS (CDGPS) technology, a single inexpensive GPS receiver can measure a vehicle’s position to within a few centimeters and heading to within 0.1˚. The ability to provide accurate real-time information about multiple vehicle states makes CDGPS ideal for automatic control of vehicles.

In this work, a CDGPS-based steering control system was designed, simulated, and tested on a large farm tractor. A highly simplified vehicle model proved sufficient for accurate controller design. After various calibration tests, closed-loop heading control was demonstrated to a one- accuracy of better than 1˚, and closed-loop line tracking to a standard deviation of better than 2.5 cm. Future plans for research include the use of a pseudo-satellite to eliminate any position bias and extending the current control system to control a towed implement.

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