Gravity Gradiometer Torque Cancellation via Counterweights
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Solution Overview
Problem
Gravity gradiometers face challenges in accurately measuring gravity gradients while airborne due to aircraft accelerations, which cause torques that overwhelm the signals from gravity gradients, making it difficult to distinguish spatial variations from temporal fluctuations.
Innovation Solution
A gravity gradiometer design featuring at least two pivotable sensor masses that experience changes in torque in response to gravity gradients, accompanied by an acceleration sensor and an actuator that generates an adjustment force to reduce the difference in torques experienced by the sensor masses, using a feed-forward control arrangement and mechanical response parameters like mass dipole moments to stabilize measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a gravity gradiometer uses sensor masses to measure gravity gradients, then measurement precision is improved, but aircraft accelerations generate large torques that overwhelm the gravity gradient signals
Solution Approach 1:
The patent uses counterbalancing masses positioned opposite the sensor masses to generate counteracting torques that cancel the harmful aircraft acceleration torques. The counterbalancing masses are adjusted to create equal and opposite moments about the pivot axis, thereby neutralizing the disturbing acceleration effects while preserving the gravity gradient measurement capability.
Solution Approach 2:
The patent implements a feedback control system using acceleration sensors to detect aircraft acceleration and actuators to adjust the counterbalancing masses in real-time. The feedback loop continuously monitors the acceleration environment and dynamically adjusts the counterbalancing configuration to maintain torque cancellation, enabling precise gravity gradient measurements despite varying aircraft motion.
2Measurement precision
If the sensor masses are made highly sensitive to torque changes, then measurement precision is improved, but the sensor becomes more vulnerable to noise from aircraft accelerations
Solution Approach 1:
The patent introduces counterbalancing masses as an intermediary element between the sensor masses and the aircraft acceleration environment. These intermediary masses absorb and cancel the acceleration effects before they reach the sensitive sensor masses, allowing the sensors to maintain high torque sensitivity without being overwhelmed by acceleration noise.
Solution Approach 2:
The patent creates a copy of the sensor mass configuration with counterbalancing masses that replicate the torque characteristics. By positioning and adjusting these copy masses to produce equal and opposite torques, the system cancels the harmful acceleration effects while the original sensitive sensor masses continue to measure gravity gradients with high precision.
3Adaptability or versatility
If the gravity gradiometer is designed for airborne deployment, then adaptability is improved, but the complexity of compensating for aircraft accelerations increases
Solution Approach 1:
The patent achieves multi-functionality by having the counterbalancing masses serve dual purposes: they provide structural balance for airborne deployment and simultaneously generate torque cancellation for acceleration compensation. The same mechanical components that enable airborne adaptability are used to reduce acceleration effects, thereby managing complexity through functional integration rather than adding separate systems.
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 design effectively reduces the impact of aircraft accelerations, allowing for precise measurement of gravity gradients by minimizing torque differences and stabilizing sensor movements, enabling accurate detection of gravity gradient signals even in airborne conditions.
Implementation Method 1
at least two sensor masses that are pivotable about respective axes and each experience a change in torque in response to a change in gravity gradient
Implementation Method 2
an acceleration sensor for sensing an acceleration associated with an external acceleration applied to the gravity gradiometer
Data Source
AI summary
The present disclosure provides a gravity gradiometer for detecting a gravity gradient. The gravity gradiometer comprises at least two sensor masses that are pivotable about respective axes and each experience a change in torque in response to a change in gravity gradient whereby the at least two sensor masses move relative to each other in response to the change in gravity gradient and wherein a signal indicative of the gravity gradient is generated in response to the relative movement of the at least two sensor masses. Further, the gravity gradiometer comprises an acceleration sensor for sensing an acceleration associated with an external acceleration applied to the gravity gradiometer. The gravity gradiometer also comprises an actuator for generating an adjustment force that is dependent on an acceleration sensed by the acceleration sensor. The adjustment force is also dependent on a mechanical response parameter associated with at least one of the at least two sensor masses. The adjustment force is applied such that a difference between the magnitudes of the torques experienced by the at least two sensor masses in response to the change in gravity gradient is reduced.