Ruling the waves

Alex van Deyzen: "When a KNRM rescue boat hits a wave too hard, the operator must buy a crate of beer for his shipmates." (Photo: Tomas van Dijk)

Name: Alex van Deyzen (31)
Nationality: Dutch
Promotor: Professor Rene Huijsman (Faculty Mechanical, Maritime and Materials Engineering; Ship Hydromechanics and Structures group)
Subject: Smart control of fast ships
Thesis defence: One year to go

“When there is an emergency at sea, the Royal Netherlands Sea Rescue Institution (KNRM) sends out fast ships. These small boats come to the rescue at high speeds - they can sail as fast as 35 knots. However, when the sea is rough and the waves high, these boats cannot navigate very quickly. The boats encounter waves from the front, called head waves, which lift the boat up and make it fall again behind the wave. Large acceleration occurs and causes great inconvenience for the crew, who can even be injured from the blows.

The operator therefore usually temporarily reduces the forward speed of the boat when there are rough head waves, which he does according to estimates based on experience or personal feelings about how rough the sea is. When he expects a wave to be high, and to cause an unacceptably large vertical acceleration peak, the operator temporarily reduces the speed. This is called thrust control. Sometimes they estimate correctly, sometimes they don’t. It could happen that a wave is higher or less high than expected, with the result being that the wave hits the boat hard or forces the operator to reduce speed, when in fact it was unnecessary to do so.
I’m therefore working on a thrust control system for fast ships - not only for ships like KNRM’s search and rescue vessels but also pilot boats, interceptors and patrol vessels. The control system anticipates the magnitude of vertical acceleration peaks in real-time and reduces the forward speed of the vessels if necessary. This must result in an increase of operability. In future the system should use a state of the art wave measuring system, based on radar, lidar or laser. However, such a system does not yet exist, but hopefully radar specialists will create one in the near future. If so, it could be implemented in the thrust control system I am working on.

My system uses predictions of the ship’s response for the coming 2 to 6 seconds. Subsequently, the predictive control system calculates what the impact will be on the boat and whether it is necessary to reduce speed. It seems that a boat could sail 5 knots faster with my system. During the coming year I will conduct tests in our 142 metre-long towing tank. It will be very exciting to see if my thrust control system also works in model scale.

I know that when a KNRM rescue boat hits a wave too hard, the operator must buy a crate of beer for his shipmates. Hopefully, thanks to the system I’m currently developing, that will soon no longer be necessary.”