Piezoelectric Ballast Control for Small Submersible Depth Trim
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Solution Overview
Problem
Small submersibles face challenges in controlling depth due to changes in water density caused by temperature and salinity variations, leading to inefficient buoyancy control and reduced range and endurance, and lack suitable variable ballast systems that are scalable and power-efficient.
Innovation Solution
A piezoelectric fluid pump system that varies the vehicle's ballast by transferring fluid between internal and external bladders, controlled by a microprocessor, allowing precise buoyancy adjustments without relying on propulsion, and includes an emergency backup system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional pumps are used for ballast control, then sufficient pressure and flow can be achieved, but the system becomes too large and consumes too much power
Solution Approach 1:
The patent replaces conventional mechanical pumps with a piezoelectric pump that utilizes piezoelectric effect to generate the necessary pressure and flow for ballast control. This substitution eliminates the need for large brushless DC motors and auxiliary components, achieving sufficient pumping capability with dramatically reduced size and power consumption suitable for small submersibles
Solution Approach 2:
The invention changes the operating parameters by using piezoelectric actuation at high frequency to achieve the required fluid displacement. The piezoelectric pump operates at frequencies and pressure levels that were previously unattainable with conventional mechanical pumps of comparable size, enabling effective ballast control in a compact package
2Ease of operation
If propulsion system is used for depth control, then depth adjustment is possible, but battery power is drained continuously reducing range and endurance
Solution Approach 1:
The patent extracts the depth control function from the propulsion system by implementing a dedicated variable ballast system. This separates buoyancy control from forward motion, allowing the vehicle to adjust depth independently without continuous propulsion, thereby eliminating the parasitic power consumption that limited range and endurance
3Measurement precision
If variable ballast system is implemented, then precise depth control and extended range are achieved, but system complexity increases
Solution Approach 1:
The patent merges multiple functions into the piezoelectric pump component, which simultaneously provides pressure generation, flow control, and precise fluid displacement for ballast adjustment. This integration eliminates the need for separate control valves, accumulators, and plumbing systems that would otherwise increase complexity
Solution Approach 2:
The piezoelectric pump is directly controlled by a microprocessor that receives depth feedback and autonomously adjusts ballast volume to maintain commanded depth. The system self-regulates buoyancy without requiring complex mechanical control mechanisms or continuous manual intervention
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 precise depth control and extended range and endurance by minimizing battery power consumption, while being compact and scalable for small submersibles, with an emergency backup to ensure safe operation.
Implementation Method 1
A piezoelectric fluid pump controls the ballast system. The pump can satisfactorily move fluid between the internal reservoir tank and an external bladder by producing 500 psi at 0.25 LPM
Implementation Method 2
A submersible vehicle must be able to develop states of positive, neutral, and negative buoyancy to control vehicle depth in the water. The equation for buoyancy is B=ρ×V×g
Data Source
AI summary
A ballast control system is used which fits small submersible vehicles. The system is used to vary the vehicle ballast in comparison to the surrounding water without the need for the propulsion system to regulate the depth. A piezoelectric fluid pump controls the ballast system and can reach depths to 1,000 ft. The pump moves fluid between an internal reservoir and an external bladder in a very small package and weight. The ballast control system uses typical underwater battery voltages. The pumping system does not need auxiliary devices. The system can be configured to trim the attitude of the vehicle along its longitudinal and/or lateral axes. The invention provides these capabilities with minimal drain on the vehicle's battery system and impact on the vehicle's payload capacity. An emergency system ensures that the submersible vehicle returns to the surface when power is lost.