Photographic Imaging Systems to Measure Fertiliser Granule Velocity During Spreading

Keywords: fertiliser spreading, image processing, spread pattern.

The aim of the research is to develop low cost high speed photographic imaging systems to measure outlet velocity of fertiliser granules during spreading. Two designs are presented in the paper. Although mechanically simple, centrifugal spreaders used for mineral fertilisation involve complex physics that cannot be fully characterised at the present time. Two parameters have to be controlled on each disc: the flow of fertiliser and the spatial distribution on the ground. Both sensors are developed to evaluate the spatial distribution of the fertiliser on the ground based on the measurement of initial flight conditions of fertiliser granules after their ejection by the spreading disc. ENESAD aims at developing a sensor for site specific fertilisation using centrifugal spreaders and a spreader prototype to replace the measurements done in test halls. CLO wants to develop a test device to evaluate spread patterns, at farm level and to replace the time consuming distribution measurements done with collector trays. The first techniques developed are based on the analysis of images of the area around the disc showing the granule ejection. High resolution – low cost imaging systems for the analysis of high speed particle projection developed for this specific purpose are presented in this paper.

The ENESAD system is based on a camera and a sequence of flashes while the CLO system uses a photo camera and a LED-stroboscope. Both systems characterise the centrifugal spreading of fertiliser particles ejected at speeds of approximately 30 m/s. It automatically computes the direction of ejection and velocity of each granule observed in the image. Multi exposure images collected with the camera installed vertically above the output flow of granules are analysed to estimate the trajectories of the fertiliser granules, using different motion estimation methods.

The results have been used in very simple ballistic model to predict the transverse spread pattern of fertiliser on the ground.

This paper describes the work done by the two research Institutes, the ENESAD and the CLO.

F Cointault, ENESAD, DSI — UMR CPAP Cemagref/ENESAD, 26, Bld Dr Petitjean, 21000 Dijon, France.

J Vangeyte, CLO Department Mechanization, Labour, Buildings, Animal Welfare and Environmental Protection, Burg. Van Gansberghelaan, 115 9820 Merelbeke, Belgium.

28 pages, 12 figures, 1 table, 13 references.