Twin-Propeller Thruster Flow Alignment for Stable Marine Turns
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Solution Overview
Problem
Existing marine vehicles with twin-propeller vector propulsion systems face difficulties in controlling trajectory, particularly during turns, due to inefficiencies in propeller flow dynamics, leading to potential destabilization and increased hydrodynamic drag.
Innovation Solution
A method for piloting marine vehicles using a vector propulsion system with two counter-rotating propellers, adjusting their cyclic and collective pitch angles to control the thrust orientation over 4π steradians, ensuring the flow from one propeller aligns with the center of the other propeller, even during turns, thereby stabilizing the vehicle's trajectory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional propulsion with control surfaces is used, then the vehicle can be steered by generating fluid flow around control surfaces, but the control surfaces generate significant hydrodynamic drag that consumes energy
Solution Approach 1:
The invention extracts and eliminates the control surfaces from the conventional propulsion system, retaining only the propeller thrust generation capability. By removing the control surfaces that cause drag, the system achieves steering through direct thrust vectoring without the energy-consuming drag penalty of traditional control surfaces.
Solution Approach 2:
Instead of using control surfaces to redirect fluid flow for steering (conventional approach), the invention inverts the approach by directly steering the thrust vector through propeller orientation control. This reversal eliminates the intermediate control surfaces and their associated drag losses.
2Adaptability or versatility
If control surfaces are used for steering, then the vehicle can change direction, but the control surfaces generate drag proportional to the square of speed which opposes movement
Solution Approach 1:
The invention extracts and removes the control surfaces from the system entirely, achieving directional control through alternative means (propeller thrust vectoring) that do not generate the harmful drag associated with control surfaces.
Solution Approach 2:
The invention converts the propeller thrust, which in conventional systems is purely for propulsion, into a dual-purpose element that provides both propulsion and steering control. This eliminates the need for separate control surfaces and their associated drag.
3Ease of operation
If the flow velocity around control surfaces is weak, then the efficiency of control surfaces decreases inversely with the square of flow velocity, but increasing flow velocity requires significant vehicle movement
Solution Approach 1:
Instead of relying on fluid flow around control surfaces for steering (which requires high vehicle speed), the invention inverts the approach by directly controlling the thrust vector orientation through propeller positioning, enabling effective steering even at low or zero vehicle speed.
Solution Approach 2:
The propeller thrust serves both propulsion and steering functions simultaneously. The system uses its own thrust generation capability to achieve directional control without requiring external fluid flow conditions or additional control surfaces.
4Object-generated harmful factors
If twin-propeller vector propulsion system is used to eliminate control surfaces, then hydrodynamic drag is reduced, but difficulties arise in controlling trajectory particularly when turning
Solution Approach 1:
The invention employs dynamic control of the twin propellers, where each propeller's thrust magnitude and orientation are continuously adjusted based on real-time vehicle state and desired trajectory. This dynamic coordination enables precise trajectory control during turns while maintaining the drag-reduction benefits of having no control surfaces.
Solution Approach 2:
The trajectory control system uses feedback from vehicle position, orientation, and speed measurements to continuously adjust propeller thrust vectors. This closed-loop control ensures accurate trajectory tracking during maneuvers while exploiting the low-drag configuration of the control-surface-free design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enhances maneuverability and reduces hydrodynamic drag by eliminating the need for control surfaces, allowing efficient steering and stabilization at various speeds without energy-consuming vortex formation.
Implementation Method 1
a propeller comprising two propellers... the upstream propeller generating a flow directed towards the position of the center of the downstream propeller
Implementation Method 2
the orientation of the control surfaces causes a modification of the lift generated by the flow of fluid surrounding the control surfaces
Implementation Method 3
the control surfaces generate a drag proportional to the square of the speed which opposes the movement and which therefore consumes energy
Data Source
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AI summary
The invention relates to a method for controlling a thruster of a marine vehicle (1) including a body (2) and a thruster (3) mounted on the body (2) of the vehicle (1). The vehicle (1) is at least partially submerged in a liquid, moves, relative to the liquid, along a movement axis (x) in a movement direction, and rotates about at least one axis of rotation perpendicular to the movement axis (x) at a rotational speed. The thruster (3) includes an upstream propeller and a downstream propeller along the movement axis in the movement direction. The method includes a stabilization step, during which the thruster is controlled such that the main axis of the upstream flow generated by the upstream propeller at a given time t is an estimated main axis on which a position (P) of a center of the downstream propeller, substantially located on the axis of rotation of the downstream propeller, is estimated to be located at a later time t+dt, at which the flow generated by the upstream propeller at the given time t reaches the downstream propeller. The estimated main axis (xe) depends on the rotational speed of the vehicle.