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Development of a robotic greenhouse sprayer can provide more accurate spraying of pesticides and fungicides, reduce operational costs, and decrease health risks associated with human exposure to dangerous chemicals. A visual navigation system capable of tracking a path, detecting intersections, and navigating through intersections was developed for a six-wheel differential steering vehicle.

Path navigation was accomplished using digital images taken from a single CCD camera mounted on a robotic greenhouse sprayer. Intersection detection was accomplished by first classifying pixels of an image as path or non-path. Left and right path edges were determined from the threshold image using least squares fitting. Path pixels extending beyond a specified distance from the left and right edges indicated an approaching intersection. The distance from the vehicle to the intersection was estimated based on the set position and orientation of the camera using projective geometry. Path following was carried out by reducing path error between the vehicle center and path center using a PID controller. Intersection navigation was accomplished by 1) tracking ground features to guide the vehicle to a desired position in the intersection, 2) proceeding with a turn, and 3) concluding when the vehicle was aligned with the next path. Testing verified the vehicles ability to follow a path, detect intersections, and navigate intersections. A more detailed report of this study is available from Younse (2005).