Design of an omnidirectional propulsion system for small jet-boats

Jet-boats perform remarkably well at high-speed but lack low speed maneuverability for tight maneuvers such as ducking. This paper presents a low speed omnidirectional propulsion system controlled with a joystick for jet-boats. Two concepts are presented and evaluated. The first concept uses all original parts. The second concept uses a set of fix jet nozzles disposed around the hull. The position and angles of the nozzles are optimized with an index of omnidirectionality quality based on the projection of a set of force solutions on a shell with the shape of the desired force space. A 3D simulator backed by experimental results serves for the evaluation by potential customers of each design. The first concept exhibited poor maneuverability, as it offers ten times less force in sway than in surge. The optimized force space of the second concept is much more uniform, and was unanimously appreciated for its quality of low speed maneuverability. Both designs have been validated experimentally. The present work offers an omnidirectional propulsion system that is easy to enhance with advanced control laws. Velocity feedback control is given as example, and shows important improvement of maneuverability and robustness to miscalibration.