Vertical Folded Pendulum for Low-Frequency Seismic Sensing
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Solution Overview
Problem
Existing mechanical systems for measuring absolute vertical displacement, particularly at low frequencies, face limitations due to low resonance frequency, sensitivity to ambient noises, and complexity in realization and calibration, with existing solutions being non-dimensional and sensitive to thermal noise and environmental factors.
Innovation Solution
A vertical folded pendulum with tunable oscillation frequency, utilizing a support, test mass, simple pendulum, and inverted pendulum connected by joint systems, with external forces applied to calibrate and adjust the resonance frequency, allowing for efficient decoupling of vertical motion from other degrees of freedom and reduced sensitivity to ambient noises.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a mechanical oscillating system with very low resonance frequency is used for vertical displacement measurement, then sensitivity at low frequencies is improved, but the system becomes sensitive to ambient noises and requires large dimensions
Solution Approach 1:
The patent applies dynamics by making the pendulum system tunable through variable external forces (magnetic, gravitational, or elastic). The resonance frequency can be dynamically adjusted by changing the magnitude of these forces, allowing the system to adapt to different measurement requirements while maintaining low-frequency sensitivity without being fixed to a single frequency point
Solution Approach 2:
The patent changes physical parameters by introducing variable external forces that modify the effective gravitational acceleration acting on the pendulum. By adjusting the magnitude of magnetic forces, gravitational forces, or elastic forces, the resonance frequency parameter can be tuned, enabling the system to achieve low-frequency operation with reduced sensitivity to ambient noises
2Ease of manufacture
If the pendulum is positioned in horizontal configuration, then the system is well-established, but compact realizations and decoupling of vertical degree of freedom are not achieved
Solution Approach 1:
The patent inverts the traditional horizontal pendulum configuration by rotating it to vertical orientation. This inversion allows the pendulum to achieve compact realizations while maintaining the folded structure's advantages. The vertical configuration enables better decoupling of the vertical degree of freedom from horizontal movements, addressing the limitations of the conventional horizontal setup
3Adaptability or versatility
If external forces are applied to tune resonance frequency, then frequency tunability is improved, but system complexity increases
Solution Approach 1:
The patent replaces complex mechanical tuning mechanisms with simpler force-based tuning using magnetic, gravitational, or elastic forces. Instead of mechanically adjusting the pendulum's physical structure to change frequency, the system uses variable external forces that can be adjusted independently, reducing mechanical complexity while maintaining frequency tunability
Solution Approach 2:
The patent applies universality by using multiple types of external forces (magnetic, gravitational, elastic) that can serve both as the restoring force for oscillation and as the tuning mechanism. This multi-functionality allows a single force system to provide both the oscillation mechanism and frequency control, reducing overall system complexity
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
The solution enables the creation of compact, high-sensitivity seismic sensors with low frequency operation and reduced noise sensitivity, achieving scalable and tunable resonance frequencies, overcoming the limitations of existing systems by using a monolithic block with elliptic joints and magnetic forces for calibration.
Implementation Method 1
the value of the gravitational acceleration, g, by applying on the pendulum, on the inverted pendulum and/or on the central mass a variable external force having a direction parallel to the gravity force vector
Implementation Method 2
a variable external force having a direction parallel to the gravity force vector, in order to vary the value of the gravitational acceleration
Data Source
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AI summary
The present invention concerns a folded pendulum, that can be realized even as a monolithic pendulum, that is not positioned in its traditional horizontal configuration, and as such developed and known in the prior art, rather in the vertical configuration, i.e. rotated by 90°, either in the clockwise or anticlockwise direction. In particular, the version of such vertical folded pendulum in monolithic configuration allows more compact realizations, characterised by high decouplings of the vertical degree of freedom from the other degrees of freedom as well as optimal mechanical quality factors.