Gravity Gradiometer Electrostatic Tuning for Airborne Noise

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Solution Overview

Problem

Existing gravity gradiometers face challenges in distinguishing spatial variations of the gravitational field from temporal fluctuations when mounted in moving vehicles, leading to noise interference that complicates the measurement of gravity gradients.

Innovation Solution

The method involves using a pair of transversely arranged sensor masses with capacitors to apply bias voltages, electronically tuning their resonance frequencies and sensitivities to ensure identical properties, allowing for precise measurement of gravity gradient components by compensating for unwanted accelerations and enhancing sensitivity and spatial resolution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the gravity gradiometer is mounted in an aircraft and carried while making measurements, then the device can perform airborne measurements, but the movements of the aircraft create accelerations that produce noise and swamp actual gravity gradient signals

Engineering Contradiction:

Improveairborne measurement capabilityVSAvoidgravity gradient measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent employs resonance at a specific frequency to enhance the sensor masses' response to gravity gradient variations. By operating at resonance, the system amplifies the desired gravity gradient signal while the common-mode acceleration effects cancel out, improving signal-to-noise ratio in airborne measurements

Inventive Principle:

Principle #18Mechanical vibration

Solution Approach 2:

The patent uses capacitive sensing to detect the position of sensor masses and feeds this information back to control the driving frequency. This feedback mechanism allows the system to maintain resonance conditions and compensate for aircraft movements, thereby reducing noise and improving measurement precision

Inventive Principle:

Principle #23Feedback

2Measurement precision

If the sensor masses are continuously rotated and operated at resonance frequency to increase sensitivity, then the measurement sensitivity improves, but the device complexity increases due to the need for precise frequency control and mass balancing

Engineering Contradiction:

Improvegravity gradient detection sensitivityVSAvoidfrequency control and mass balancing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical frequency control mechanisms with an electrical control system. Capacitive sensors detect mass position, and electronic circuits adjust the driving frequency to maintain resonance, simplifying the overall system while improving sensitivity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent dynamically adjusts the driving frequency parameter to match the resonance frequency of the sensor masses. This parameter change optimizes the sensor response and enhances sensitivity to gravity gradient variations while maintaining manageable system complexity through electronic control

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If the bandwidth associated with resonant oscillation is increased to improve spatial resolution, then the spatial resolution improves, but the resonance frequency stability becomes more difficult to maintain

Engineering Contradiction:

Improvespatial resolutionVSAvoidresonance frequency stability

Core Design Contradiction:

Measurement precisionVSStability of the object's composition

Solution Approach 1:

The patent employs capacitive feedback to continuously monitor the sensor mass position and adjusts the driving frequency in real-time. This feedback loop maintains resonance stability even as the bandwidth is increased to improve spatial resolution, resolving the contradiction between resolution and stability

Inventive Principle:

Principle #23Feedback

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 approach effectively reduces noise interference and enhances the sensitivity and spatial resolution of gravity gradient measurements, enabling more accurate detection of changes in the gravitational field, even in airborne applications.

Implementation Method 1

applying a bias voltage to at least one of the capacitors for generating an electrostatic force which acts on one of the sensor masses and thereby influences the movement of that sensor mass

Methodology Applied

Scientific EffectElectrostatic force: Electrostatics

Implementation Method 2

a pair of first and second transversely arranged sensor masses that are arranged for movement about an axis and relative to each other in response to a gravity gradient

Methodology Applied

Scientific EffectGravity gradient: Gravitation

Data Source

PatentUS8033170B2Gravity gradiometer

Publication Date: 2011.10.11 TECHNOLOGICAL RESOURCES PTY LTD

AI summary

The present invention provides a method of tuning properties of a gravity gradiometer for measuring components of the gravity gradient tensor. The gravity gradiometer comprises a pair of first and second transversely arranged sensor masses that are arranged for movement about an axis and relative to each other in response to a gravity gradient. The gravity gradiometer further comprises first and second capacitors for sensing and influencing the movement of the first and second sensor masses. The method comprising applying a bias voltage to at least one of the capacitors for generating an electrostatic force which acts on one of the sensor masses and thereby influences the movement of that sensor mass.