Parallel Dipole Line Trap Seismometer for Weak Motion Detection

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Solution Overview

Problem

Current seismometers, particularly those for low-cost and high-sensitivity weak motion detection, are lacking in effectively measuring seismic activity, with existing designs being either too complex or insufficient in sensitivity.

Innovation Solution

A magnetic parallel dipole line (PDL) trap seismometer system utilizing a pair of dipole line magnets and a diamagnetic object levitating above them, with a sensing system to determine the object's position relative to the magnets, allowing for the detection of seismic vibrations by measuring the displacement of the levitated object.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional pendulum-based or piezoelectric seismometers are used, then strong motion detection is achieved, but weak motion detection sensitivity is insufficient

Engineering Contradiction:

Improveweak motion detection sensitivityVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces traditional mechanical pendulum-based seismometer systems with a magnetic levitation system using diamagnetic materials and magnetic fields. This substitution eliminates mechanical contact and friction, enabling detection of much weaker seismic motions while maintaining system simplicity through the use of standard magnetic components

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the operating parameters by using diamagnetic levitation to suspend the proof mass, operating in a contactless magnetic field environment. This parameter change from mechanical support to magnetic field support enables detection of weak motions below 1 ng/Hz^0.5 while keeping the device structure relatively simple

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If high sensitivity seismometers are designed, then weak motion detection capability is improved, but cost and complexity increase

Engineering Contradiction:

Improveseismic noise detection thresholdVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent uses inexpensive diamagnetic materials such as pyrolytic graphite or water as the levitated proof mass, replacing expensive precision mechanical components. These simple materials can be easily obtained and manipulated, significantly reducing manufacturing cost while achieving high sensitivity detection

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

By replacing complex mechanical suspension systems with magnetic levitation, the patent eliminates the need for precision mechanical bearings, springs, and dampers, thereby reducing manufacturing complexity and cost while achieving superior sensitivity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If magnetic levitation is used for weak motion detection, then sensitivity is improved, but environmental sensitivity and noise increase

Engineering Contradiction:

Improvevibration detection sensitivityVSAvoidenvironmental sensitivity

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent employs magnetic field shielding and can operate in controlled environmental conditions, creating an inert magnetic environment that protects the levitated proof mass from external magnetic interference. This shielding approach reduces environmental sensitivity while maintaining the high sensitivity needed for weak motion detection

Inventive Principle:

Principle #39Inert atmosphere (Inert environment)

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 PDL trap seismometer achieves high sensitivity and low noise detection, capable of detecting seismic noise less than 1 ng/Hz^0.5, with a bandwidth of 0.1 Hz to 10 Hz, peak acceleration less than 0.25 g, and a dynamic range of over 120 decibels, while maintaining a simple and cost-effective design.

Implementation Method 1

a diamagnetic object levitating above the dipole line magnets

Methodology Applied

Scientific EffectDiamagnetism: Diamagnetism

Data Source

PatentUS10983230B2Parallel dipole line trap seismometer and vibration sensor

Publication Date: 2021.04.20 INTERNATIONAL BUSINESS MACHINE CORPORATION

AI summary

Parallel dipole line (PDL) trap seismometer and vibration sensors are provided. In one aspect of the invention, a seismometer is provided. The seismometer includes: at least one PDL trap having a pair of dipole line magnets, and a diamagnetic object levitating above the dipole line magnets; and a sensing system (passive or active sensing) for determining a position of the diamagnetic object relative to the dipole line magnets and to yield the seismic signal in terms of displacement or acceleration. Methods for sensing vibrations using the present PDL trap seismometer and vibration sensors are also provided.