Simple imaging system to measure velocity and improve the quality of fertilizer spreading in agriculture

The management of mineral fertilization using centrifugal spreaders calls for the development of spread pattern characterization devices to improve the quality of fertilizer spreading. In order to predict spread pattern deposition using a ballistic flight model, several parameters need to be determined, in particular, the velocity of the granules when they leave the spinning disc. We demonstrate that a motion-blurred image acquired in the vicinity of the disc by a low-cost imaging system can provide the three-dimensional components of the outlet velocity of the particles. A binary image is first obtained using a recursive linear filter. Then an original method based on the Hough transform is developed to identify the particle trajectories and to measure their horizontal outlet angles, not only in the case of horizontal motion but also in the case of three-dimensional motion. The method combines a geometric approach and mechanical knowledge derived from spreading analysis. The outlet velocities are deduced from outlet angle measurements using kinematic relationships. Experimental results provide preliminary validations of the technique.