Flexible Sensing Element for Intrinsic Gravity Gradiometer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing gravity gradiometers face challenges in accurately measuring direct gravity gradients due to coupling with gravitational and kinematic acceleration, leading to complex manufacturing processes and high costs, and they require multiple readings or spatially separated sensors, which limits their sensitivity and stability.
Innovation Solution
A flexible, elongate sensing element with free ends and multiple rotational pivots is used, allowing for single-point measurement of direct gravity gradients without tension, enabling improved sensitivity and stability through modulation-demodulation of signals to eliminate zero-point drift and reduce unwanted mechanical degrees of freedom.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple spatially separated sensors or multiple readings are used to measure gravity gradients, then measurement coverage is improved, but device complexity and cost increase
Solution Approach 1:
The sensing element is divided into multiple segments along its length, with each segment having specific pivot points that allow independent rotational movement. This segmentation enables the single element to detect multiple gravity gradient components (Gxx, Gyy, Gzz, Gxy, Gxz, Gyz) simultaneously through differential measurements at different segments, eliminating the need for multiple separate sensors.
Solution Approach 2:
The single flexible sensing element serves multiple functions: it acts as both the structural support and the measurement transducer. By configuring multiple rotational pivots along its length, one sensing element can measure all six independent gravity gradient components, making it a universal sensor that replaces what would traditionally require multiple separate gravimeters or gradiometers.
2Stability of the object's composition
If the sensing element is held under tension between fixed ends, then structural stability is improved, but coupling with gravitational and kinematic acceleration increases
Solution Approach 1:
The sensing element transitions from a static, tension-held configuration to a dynamic configuration with multiple rotational pivots. Each pivot point can rotate freely, allowing the element to adapt its shape in response to gravity gradients while maintaining stability. The dynamic degrees of freedom at each pivot enable the system to distinguish between gravity gradient effects and acceleration effects through differential measurements.
Solution Approach 2:
The boundary conditions of the sensing element are changed from fixed ends to free ends with intermediate rotational pivots. This parameter change in the mechanical constraints allows the element to respond differently to various forces: gravity gradients cause differential rotations at the pivots, while uniform acceleration affects all pivots equally and can be rejected through differential measurement techniques.
3Object-affected harmful factors
If a string-like object with fixed ends and clamped mid position is used, then C-mode dynamic motion is eliminated, but unwanted mechanical degree of freedom (W-mode or sag mode) remains
Solution Approach 1:
Instead of a single clamped mid-position constraint, the sensing element is divided into multiple segments with rotational pivots at specific locations along its length. This segmentation replaces the single clamping point with multiple controlled rotation points, each contributing to the elimination of unwanted modes while preserving the desired sensitivity to gravity gradients.
Solution Approach 2:
The mechanical clamping constraint is replaced with rotational pivot joints. These pivots provide the necessary constraints to eliminate unwanted modes like C-mode and W-mode, while still allowing the sensing element to respond to gravity gradients through differential rotations. The pivot mechanism substitutes the rigid clamping with a more flexible joint that achieves the same mode suppression without the harmful side effects.
4Measurement precision
If the sensing element is moved to another location to derive gravity gradient differences, then measurement capability is improved, but intrinsic measurement capability is reduced
Solution Approach 1:
The sensing element is designed to measure all six independent gravity gradient components (Gxx, Gyy, Gzz, Gxy, Gxz, Gyz) at a single location simultaneously. This universal measurement capability eliminates the need to move the sensor to different locations or take multiple separate readings, as the multi-segment configuration with rotational pivots provides complete gravity gradient information intrinsically at one position.
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 enhances the sensitivity and stability of gravity gradient measurements, allowing for intrinsic acquisition of gravity gradiometry data without moving the sensor, reduces manufacturing complexity, and effectively cancels out noise, achieving high precision at room temperature.
Implementation Method 1
the sensing element is able to flex about the connection points in response to an applied gravity field
Data Source
Figure 1~4b
Figure 5A~5B
Figure 6~9
AI summary
A sensing element (10) for an intrinsic gravity gradiometer (IGG) for use in sensing variation in a gravity field at a location. The sensing element (10) is flexible, elongate and has unfixed opposed ends (12, 14) when part of the gravity gradiometer. The sensing element can be a metallic ribbon, and can be mounted by a number e.g. 3 or 5, pivot points or axes 30-40 at each of the opposed sides along the sensing element, with the opposed ends of the sensing element free to move. The pivot points or axes can include pins, preferably cylindrical pins (48) or the sensing element may be etched within the side wall and remain joined to the remainder of the side wall by connections. The sensing element (10) can form part of one or more resonant cavities or wave guide (44, 52-66), such as a side or dividing wall (46) or part thereof. A dual phase bridge (61,612) arrangement can be provided. Electrical current (I) can be injected into the sensing element. Feed forward motion compensation (MC or FFMC) can be applied as part of the determination of the current. Applying electrical current into the opposed longitudinal sides (20, 22), such as right and left sides, of the sensing element, such as a ribbon, can be used for several types of compensation. Displacement of the sensing element can be detected by a resonant cavity, electromagnetic sensor or optical sensor.