Research Papers

Design of a Multijet Omnidirectional Propulsion System for Small Jet-Boats

[+] Author and Article Information
David Foley

Department of Mechanical Engineering, Universite de Sherbrooke, Sherbrooke, QC, J1K 2R1, Canadadavid.foley@usherbrooke.ca

Jean-Sebastien Plante

Department of Mechanical Engineering, Universite de Sherbrooke, Sherbrooke, QC, J1K 2R1, Canada

J. Mech. Des 132(11), 111008 (Nov 15, 2010) (8 pages) doi:10.1115/1.4002805 History: Received March 03, 2010; Revised October 01, 2010; Published November 15, 2010; Online November 15, 2010

Jet-boats perform remarkably well at high-speed but lack low speed maneuverability for tight maneuvers such as docking. This paper presents a joystick controlled omnidirectional propulsion system for jet-boats. The concept uses a set of fixed jet nozzles disposed around the hull. When a force is commanded by the joystick, valves on each nozzle modulate the flow so that the sum of nozzle thrusts correspond to the commanded force. The positions 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 a desired force space. The choice of valve positions and engine speeds is done by the numerical inversion of an internal viscous flow model. A 3D simulator, backed by experimental results, serves to (1) evaluate the ability of the proposed concept in meeting its design requirements and (2) develop control algorithms. Experimental results show that the proposed omnidirectional system is effective for low speed maneuverability with open-loop force control. The present work also offers an effective omnidirectional propulsion system that is easy to enhance with advanced control laws. Velocity feedback control is given as an example and shows important improvement of maneuverability and robustness to miscalibration.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Physical configuration of the proposed multijet propulsion system

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Figure 2

Force space and the cost function (discussed later)

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Figure 3

Open-loop force control in solid line and velocity feedback control in dashed line

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Figure 4

Boat’s frame of reference

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Figure 5

Flow, head, and engine speed relation of the pump

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Figure 6

The ratio between the norm of a force point and the norm of its projection on the shell, denoted as α

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Figure 7

Truss for the force measurement

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Figure 8

Snapshot of the simulator

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Figure 9

Shape of the optimized force space

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Figure 10

Improvement of the model to fit the measured forces

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Figure 11

Open-loop versus closed-loop proportional velocity feedback using a calibrated model

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Figure 12

Power spectral density of joystick commands



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