Coanda Jet Devices for Multi-Axis Underwater Robot Propulsion
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Solution Overview
Problem
Conventional propeller thrusters in underwater robots are cumbersome, difficult to control at low speeds, and generate substantial reaction moments, making them unsuitable for precise maneuvers and industrial applications like nuclear reactor inspections.
Innovation Solution
A propulsion system utilizing Coanda jet devices (CJDs) coupled with pumps to achieve multi-axis underwater control, allowing for precise translation and rotation without the need for multiple motors, using a Coanda effect valve and diffuser nozzles to manage forces and moments efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional propeller thrusters are used for underwater robot propulsion, then the robot can achieve robust and useful propulsion for many applications, but the large number of motors adds considerable mass and volume to the robot
Solution Approach 1:
The patent merges multiple propeller thruster functions into a single water jet propulsion system. Instead of using five separate propeller motors, the system uses one pump to generate a water jet that can be directed along different axes through Coanda jet devices, thereby reducing the number of motors and associated mass while maintaining propulsion capability
Solution Approach 2:
The water jet propulsion system serves multiple functions that would traditionally require separate devices. A single pump and jet system can provide propulsion in multiple directions and enable maneuvering operations, replacing the need for multiple dedicated propeller thrusters for different motion axes
2Reliability
If conventional propeller thrusters are used for underwater robot propulsion, then the robot can achieve useful propulsion capability, but the system exhibits nonlinearities which make them difficult to control when operating at very low speeds or when required to turn on and off rapidly
Solution Approach 1:
The system uses dynamic control of the Coanda jet devices to redirect the water jet flow in real-time. This allows continuous and smooth control of propulsion direction and magnitude without the nonlinear switching behavior of propellers, enabling precise control at very low speeds and rapid direction changes
Solution Approach 2:
The system replaces mechanical propeller rotation with hydraulic flow direction control. By using fluid dynamics and Coanda effect valves to redirect the water jet, the system achieves linear and predictable control characteristics that are easier to manage at low speeds compared to the nonlinear torque and thrust characteristics of electric motor-driven propellers
3Adaptability or versatility
If conventional propeller thrusters are used for underwater robot propulsion, then the robot can achieve propulsion function, but reversing the direction of a propeller exerts substantial reaction moments on the body of the vehicle
Solution Approach 1:
The system segments the propulsion function across multiple Coanda jet devices arranged along different axes. Instead of reversing a single propeller that creates large reaction moments, the system can selectively activate or redirect jets at different locations, distributing the maneuvering forces and reducing harmful reaction moments on the vehicle body
Solution Approach 2:
Instead of reversing propeller rotation to change direction, the system inverts the approach by maintaining constant pump rotation and using Coanda jet devices to redirect the water jet flow direction. This eliminates the reaction moments associated with propeller reversal while achieving the same maneuvering effect
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
Enables compact, lightweight, and precise multi-axis control of underwater robots, reducing complexity and eliminating the need for frequent pump reversals, thereby improving maneuverability and reducing mass and volume.
Implementation Method 1
A different type of valve is used. A Coanda effect valve based on fluidics technology is used as a valve, allowing the direction of the exit jet to be controlled in a high speed yet compact way.
Data Source
AI summary
A propulsion system is provided that includes one or more pumps that form a jet for propulsion. A number of Coanda jet devices (CJDs) are coupled to the one or more pumps. The CJDs are arranged so to allow for a multi-axis underwater control of an underwater robot.