Development of a High Irradiance LED Configuration for Small Field of View Motion Estimation of Fertilizer Particles.

Simon Cool,Julien Dubois,Tim Van De Gucht,Jürgen Vangeyte,Jan Pieters,Sergio Mora,Frédéric Cointault,Koen Mertens

doi:10.3390/s151128627

Abstract

Better characterization of the fertilizer spreading process, especially the fertilizer pattern distribution on the ground, requires an accurate measurement of individual particle properties and dynamics. Both 2D and 3D high speed imaging techniques have been developed for this purpose. To maximize the accuracy of the predictions, a specific illumination level is required. This paper describes the development of a high irradiance LED system for high speed motion estimation of fertilizer particles. A spectral sensitivity factor was used to select the optimal LED in relation to the used camera from a range of commercially available high power LEDs. A multiple objective genetic algorithm was used to find the optimal configuration of LEDs resulting in the most homogeneous irradiance in the target area. Simulations were carried out for different lenses and number of LEDs. The chosen configuration resulted in an average irradiance level of 452 W/m2 with coefficient of variation less than 2%. The algorithm proved superior and more flexible to other approaches reported in the literature and can be used for various other applications.

Highlights

In Europe, more than 90% of granular fertilizer spreaders are centrifugal spreaders [1,2], mainly because of their low cost and the large working width [3]
The aim of this paper is to create a high irradiance lighting system which will be used in future experiments for motion estimation of fertilizer particles using stereovision
Based on preliminary fertilizer spreading experiments, it was determined that a minimum irradiance of 450 W/m2 will be necessary

Summary

Introduction

In Europe, more than 90% of granular fertilizer spreaders are centrifugal spreaders [1,2], mainly because of their low cost and the large working width [3]. Spreader manufacturers provide spread charts for the user to find the optimal spreader settings for a given fertilizer and a chosen working width These are determined by measuring the mass distribution of fertilizer on the ground. A totally different approach is to model the behavior of fertilizer particles and predict their landing positions based on a ballistic flight model These landing positions cannot be predicted without knowing the velocity (typically 20–35 m/s) and direction of motion of individual particles. More recent approaches are inspired by Particle Image Velocimetry (PIV), where tracer particles are seeded in a fluid to predict global velocity fields of flows based on motion of individual particles [7] They use image acquisition and processing to determine two or three dimensional information about the moving particles. Cointault et al proposed a multi exposure image acquisition system using a series of flashes and a field of view of 1 m ×1 m allowed capturing one throw of fertilizer

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