Kristoffer Rist Skøien

Modelling spatial surface pellet distribution from rotary pneumatic feed spreaders

This paper presents a combined robotic and external ballistic model to predict the feed pellet distribution pattern across the water surface generated by a pneumatic rotary feed spreader commonly used in sea cage aquaculture. Results from experimental studies have been used to parameterize and validate the model. The model can be applied to evaluate spreader performance under varying operational conditions as well as exploring alternative spreader designs and configurations in order to optimize pellet distribution and feed utilization with respect to fish growth and welfare.

A computer vision approach for detection and quantification of feed particles in marine fish farms

In the realm of marine fish farming, there is increased focus on employing numerical models and tools to optimize production. A model describing the distribution of pelleted fish feed in time and space within a sea cage, a process which is essential for proper fish growth and welfare, has been established, but proper data for model validation have been scarce. A device based on computer vision which is able to accurately quantify the feed density within a specified volume of the sea cage as a function of time was thus developed. This paper describes the physical design of the device, as well as the application and combination of well-established algorithms to reliably detect and quantify feed pellets. Results from tests using realistic feed densities showed that the device was capable of detecting and quantifying with an error of 1.3 %.

A communication bridge between underwater sensors and unmanned vehicles using a surface Wireless Sensor Network — Design and validation

This paper presents a conceptual design and field test validation of a network of surface nodes providing a communication bridge between underwater sensors and Unmanned Vehicles (UV). Here we describe the combined operations of custom made low-cost buoys and Unmanned Aerial Vehicles (UAV), linked together within one network. Buoys equipped with an underwater acoustic telemetry receiver and water parameter sensors were moored in a Norwegian subarctic fjord and the underwater sensor data and settings were made accessible via the buoys to a surface mesh-type Wireless Sensor Network. The paper describes the design and implementation of buoy hardware and software, as well as results and experiences acquired through field experiments with the system.

Feeding of large-scale fish farms: Motion characterization of a pneumatic rotor feed spreader

This study presents a wireless attitude heading and reference system (AHRS) adapted for use in marine environments where it was used to characterize the motion of a pneumatic rotary feed spreader representative of designs commonly utilized in large-scale salmon aquaculture. The attitude of the spreader affects the distribution of feed pellets over the cage surface and may have significant influence on the feeding efficiency of fish. Measurement and analysis of the motion were performed over a range of different airspeeds. The results suggested that an angular momentum originating from the connection between the spreader and the feed supply pipe may cause a substantial roll offset. At low airspeeds the yaw angle of the outlet pipe appeared to be most influential on the roll and pitch of the spreader. At higher airspeeds the rotational velocity became increasingly influential. The roll and pitch of the spreader may explain the non-uniform surface pellet distribution observed in a separate study.

Effects of wind on surface feed distribution in sea cage aquaculture: A simulation study

This study examines the simulated effects of wind on the spatial surface distribution of pelletized feed from rotary pneumatic spreaders which are used extensively in sea cage aquaculture. A robotic model of the spreader and external ballistic description of the pellet trajectories have been extended to include wind forces, and the spatial distribution is compared for different sized pellets in various wind fields. The results show that overall effects of wind on spatial pellet distribution is limited, however, there is a negative correlation between wind and surface coverage.

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

Abstract 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.