Manufacture of Propulsion Systems for Micro Underwater Vehicles

Underwater vehicles have been used in many ocean exploration and rescue applications. Recent researches are trending toward the vehicle’s application in smaller regions. As size of the parts decreases, challenges exist in the manufacturing of critical components which are hard to obtain commercially. This paper focuses on developing the propulsion systems of the micro underwater vehicle, and exploring the feasibility of the manufacturing. The target hull size of the micro underwater vehicle that the propulsion systems use is less than 50×30×30mm. In this research, two types of propulsion systems, propeller-type and jet-type, were investigated. In the propeller-type propulsion system, a propeller with the selected electric motor was designed to generate sufficient thrust, and the blade section was based on NACA four-digit airfoils. The outer diameter of the propeller is 25 mm with a minimum blade thickness of 0.9 mm. The thin 3D blade geometry is hard to achieve by traditional manufacturing approaches. As a result, Shape Deposition Manufacturing (SDM) process, a layered manufacturing technique, was used to generate the complex 3D propeller. The thrust performance of the fabricated propeller was also compared with the theoretical thrust. The jet-type propulsion system utilized the concept of piezoelectric-actuated valveless micro-pump, and a special design with 3 inlets from the side and one outlet in the back was implemented in order to satisfy the micro underwater vehicle application. The 3D geometry of the channel with minimum width of 80 μm creates great challenges in fabrication and poses difficulty when done by traditional micro fabrication techniques. SDM process is also applied to manufacture the chamber and channels of the micropump. The piezoelectric buzzer was attached to the fabricated valveless micropump chamber for testing back pressure and flow rate. This research provides solutions to manufacture propeller-type and jet-type propulsion systems for micro underwater vehicle applications. SDM process was proved to be the suitable approach to generate small complex 3D propellers and a pre-assembled valveless micropump structure with micro channels.