Follow me – Control System

The Swedish Sea Rescue Society (SSRS) is a voluntary organization that was started 1907 and has since rescued over 25 000 ships and 70 000 people in need at sea. The following years SSRS has been rapidly growing and consists today of 68 rescue stations along the Swedish coast, 190 rescue boats and approximately 2000 voluntary lifeguards.

A commonly used rescue vehicle is the self-developed Rescuerunner, which is a kind of jet ski that is fast and efficient when it comes to rescuing people in shallow waters, where bigger boats cannot reach. Unfortunately the Rescuerunners are mostly used in the vicinity of the rescue stations due to the complicated procedure of transporting them to the scene of the accident. The problem when towing the Rescuerunner after the ego boat is that the motion becomes erratic and shaky at higher velocities, consequently leading to a chance of the Rescuerunner to capsize, i.e. turning around in the water. Another solution that has also been used is to hang the Rescuerunner on the back of the ego boat, which also has been proved inefficient since the weight of the Rescuerunner is measured to a bit over 400 kg. This weight is to big for the smaller boats to carry and the lack of space will be decreased which is not desirable when an accident has occurred and help needs to be carried out quick.

To most common solution to this problem today is that a lifeguard is maneuvering the jet ski, either on its own mission or following the ego boat to the scene of accident. This is not desirable either since it is both exhausting and hard to follow the ego boat with the Rescuerunner out on open sea. The SSRS want all the lifeguards to be able to focus on the rescue situation instead of putting a lot of effort into getting all equipment to the scene of the accident. The purpose of this thesis will therefore be to investigate the possibilities of developing a system that will enable the Rescurunner to follow the ego boat by itself and be ready alongside it when arriving at the scene of accident. In order to be able to perform this task a mathematical model for the Rescuerunner and a path following algorithm will be developed. Those two subsystems will then be combined and with the aid of computer software, e.g. MATLAB and Simulink, the functionality of the system as a whole will be evaluated. If the system works in a proper way, it will be implemented in the real Rescuerunner and tests will be performed on actual water.

The computer aided simulations are performed with a satisfactory result and now the project has currently reach its implementation state, where the path following algorithm is going to be implemented in the actual RescueRunner by using Arduino microcontrollers. The following picture is showing how a sensor containing an accelerometer and a gyroscope, is connected to the Arduino Mega Microcontroller. The gyroscope is used for determining the direction of the RescueRunner compared to the boat it is following. If the deviation is to big the task of the control system is to fix the position of the RescueRunner, making it follow the leading boat in a smooth a safe way.