Pulswing (Pulse fishing)

Our client

HFK Engineering in Baarn, an engineering firm that is active in the field of development of machines and controls, has developed the Pulswing in cooperation with the Ministry of Agriculture and Fisheries. The Pulswing is an aerodynamically designed beam on which the trawl nets are towed by a fishing cutter. This fishing principle is called beam trawling. The design of the Pulswing ensures that both the Pulswing itself and the trawl nets are towed just above the seabed. This has two important advantages:

• Fuel saving: the resistance of the fishing gear during towing is considerably lower. Practice shows that fuel savings of thousands of litres per boat per week are achieved;
• Environment: damage caused by disturbance of the seabed is greatly reduced.

Problem definition
In order to catch the fish hiding in the seabed, chains were dragged over the seabed. This still results in damage to the seabed and high fuel consumption. This gave rise to the idea of electric fishing: by sending out pulses of voltage above the seabed, the fish are chased from the seabed and then caught in the trawl. HFK Engineering asked Brunelco to develop a module that uses electrodes to generate these voltage pulses.

The solution:
Several copies of the module developed by Brunelco will be assembled per Pulswing. Each module controls an electrode. The supply voltage for the modules is supplied from the ship with a long cable.

Product features:

• High-efficiency switched mode power supply that converts the supply voltage to a safe pulse voltage that complies with the permitted values;
  Fast switching output stage that can generate a pulse current of up to hundreds of amps;
• The voltage generated on the electrodes is galvanically separated from the vessel so that it can only generate a current at the desired location in the seabed;
• Communication between the modules and the vessel by means of a fieldbus or powerline communication, control from a PLC on the vessel;
• The power provided by the electrodes can be adjusted from the ship;
• The electronics of the module are encapsulated in a watertight module that can withstand the high water pressure on the seabed, guaranteeing correct operation under the most extreme conditions;

The Brunelco pulse module has made the Pulswing operationally applicable with the above-mentioned advantages. An additional advantage of the pulse module is that discards (fish that one does not want to catch like other species or young fish) decrease considerably, which ultimately benefits the fish stock. This makes it possible to fish more selectively for both species and size.

Applied (development) tools and techniques:

• Altium Schematic entry and PCB Layout;
• Simulation tools;
• Programming language C;
• Galvanically separated RS485 bus communication;
• Powerline communication;
• Switched Mode Power Supply design;

Important principles in the design:
The design had to take into account the regulations laid down by the Ministry of Agriculture and Fisheries. In particular, the voltage levels on the electrodes, as well as the limitation in the supplied energy of the pulses, were critical factors. Partly due to the intensive cooperation with HFK Engineering and the possibilities offered to carry out tests at sea, the results are very positive.

Pulswing in practice
Pulswing has already been commercially released and the media has also paid attention to this.