Feed spreaders in sea cage aquaculture - Motion characterization and measurement of spatial pellet distribution using an unmanned aerial vehicle

Pneumatic rotary feed spreaders represent essential equipment in the feeding system of present day industrial-scale sea cage aquaculture. This study presents experimentally obtained attitude measurements and corresponding surface distribution patterns of pellets in order to characterize the dynamic behavior and performance of such spreaders. Spreader attitude and direction were measured by employing an attitude and heading reference system along with a rotary encoder. In addition, an unmanned aerial vehicle (UAV) was used to record pellet surface impacts from the air, and the position and direction of the spreader was obtained by applying computer vision methods to the recorded video. The proposed UAV method was fast to deploy, requires minimal equipment installation and presents a viable alternative to the approach of collecting pellets manually using Styrofoam boxes as reported in earlier studies. The findings from this study may be used as a base for further development and refinement with respect to using an UAV to observe the performance and spatial pellet distribution from various feed spreaders used in aquaculture. Such a tool may be valuable for farmers and equipment producers which may easily evaluate the performance of various spreader designs. In addition, the results serve as valuable input for parametrization and validation of mathematical feed spreader models.