Electrically actuated thrusters for autonomous underwater vehicle

This paper is to present the design, development and prototyping of an electrically actuated thruster as a direct drive propulsion system based on a 3-phase permanent magnet brushless machine for an autonomous underwater vehicle. The non-linear design and analysis of the permanent magnet brushless motor are entirely performed in 2-d finite element method. The motor is then coupled directly to a 6-inch mechanical propeller, thus providing a peak thrust of 25N for the AUV's manoeuvre. Critical key performances are accounted for in the analysis such as maximum speed capability, maximum output torque and efficiency at 48V_dc battery supply. Other electromagnetic considerations such as cogging torque, slot numbers and pole numbers are also addressed. Hall-effect sensors are embedded inside the motor structure in order for the motor to successfully operate in bldc mode. The optimized motor design has been prototyped and tested to work as direct drive propulsion system. The results obtained from the experiment conducted in laboratory in an open water testbed show satisfactory performance with a rated 15N continual bollard thrust at 1200rpm motor speed.