Gravity Gradiometer Sensor Mass Pivotal Coupling
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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
A gravity gradiometer design incorporating at least one sensor mass with a pivotal coupling and constant charge capacitors, where the movement of the sensor mass generates a voltage change across the capacitors, allowing for the compensation of unwanted accelerations and improved sensitivity through electrostatic forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the gravity gradiometer is mounted in a moving aircraft, then the instrument can be deployed over ground planes for exploration, but unwanted accelerations from aircraft movements create noise that swamps the actual gravity gradient signals
Solution Approach 1:
The patent applies differential measurement techniques where two sensor masses measure accelerations in opposite directions. The unwanted aircraft accelerations affect both masses equally (common-mode noise), while the gravity gradient signal causes differential movement. By subtracting the signals, the common-mode noise is eliminated and the gravity gradient measurement is enhanced.
Solution Approach 2:
The patent introduces capacitive sensing elements as intermediaries between the sensor masses and the measurement system. These capacitors convert the mechanical displacement of the sensor masses into electrical signals, enabling precise measurement of differential movements while isolating the measurement system from direct mechanical coupling with the aircraft platform.
2Reliability
If two sensor masses are used with orthogonal positioning, then unwanted accelerations can be eliminated through differential measurement, but balancing the sensor masses to have identical dynamic properties becomes technologically challenging
Solution Approach 1:
The patent employs adjustable counterweights and tuning mechanisms that allow post-manufacturing adjustment of the sensor mass parameters. This enables fine-tuning of the dynamic properties (mass, moment of inertia, natural frequency) to achieve precise matching between the two sensor masses, overcoming limitations of manufacturing tolerances.
Solution Approach 2:
The patent implements active control systems with feedback that automatically compensate for imbalances in the sensor masses. Sensors detect differential movements, and control actuators apply corrective forces to maintain balanced operation, allowing the system to self-correct manufacturing imperfections during operation.
3Measurement precision
If the instrument is continuously rotated during measurement, then sensitivity is increased by operating at resonance frequency, but the bandwidth of resonant oscillation limits spatial resolution
Solution Approach 1:
The patent employs variable rotation speed control that allows the instrument to operate at different rotational frequencies depending on the measurement requirements. The system can switch between resonance operation (for high sensitivity) and non-resonance operation (for broader bandwidth and spatial resolution), providing dynamic adaptability to different exploration scenarios.
Solution Approach 2:
The patent uses periodic modulation of the rotation speed or excitation frequency to sweep through a range of frequencies, effectively increasing the operational bandwidth while maintaining the benefits of resonant operation at specific frequencies. This frequency sweeping technique enhances spatial resolution without completely sacrificing sensitivity.
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 enhances the ability to measure gravity gradients by reducing noise interference and ensuring balanced sensor masses, thereby improving the spatial resolution and accuracy of measurements, even when the instrument is in motion.
Implementation Method 1
a constant charge capacitor arranged so that the movement of the at least one sensor mass generates a change in a voltage across the constant charge capacitor
Implementation Method 2
at least one sensor mass for movement in response to a gravity gradient
Data Source
AI summary
The present invention provides a gravity gradiometer for measuring components of the gravity gradient tensor. The gravity gradiometer comprises at least one sensor mass for movement in response to a gravity gradient and a pivotal coupling enabling the movement of the at least one sensor mass about an axis. Further, the gravity gradiometer comprises a constant charge capacitor that is arranged so that the movement of the at least one sensor mass generates a change in a voltage across the constant charge capacitor.