Bipartite Sensor Array for Geotechnical Monitoring
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Solution Overview
Problem
Conventional inclinometers and ShapeAccelArray (SAA) face limitations in long gauge lengths, high cost due to numerous sensors, lack of robustness for rocky soils, difficulty in installation, and inability to retrieve instruments after deformation, with prior-art not providing convenient, self-contained, calibrated systems for geotechnical monitoring.
Innovation Solution
A bipartite sensor array comprising a first sensory array portion with gravimetric sensors and elongate flexures capable of non-monotonic bend in two degrees of freedom, integrated with a second hollow exoskeleton portion that provides mechanical protection, allows long gauge lengths, reduces sensor count, and enables easy retrieval, using a compact, calibrated system that can be deployed and assembled in situ.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inclinometers use multiple sensors along the array to measure tilt at multiple points, then measurement precision is improved, but device complexity and cost increase due to numerous sensors and grooved casing requirements
Solution Approach 1:
The sensor array is divided into multiple rigid bodies separated by flexible joints, with sensors placed only at selected locations rather than continuously. This segmentation allows tilt measurement at key points while reducing the total sensor count and system complexity.
Solution Approach 2:
Flexible joints serve as intermediaries between rigid bodies, transmitting mechanical deformation while allowing relative movement. These joints enable the array to conform to curved paths without requiring sensors at every location, reducing complexity while maintaining measurement capability.
2Reliability
If the sensor array is made robust with thick protective casing for rocky soils, then reliability is improved, but the array cannot be retrieved after deformation due to inability to negotiate sharp curves
Solution Approach 1:
The array transitions from a rigid structure to a dynamic, adaptable system where rigid bodies connected by flexible joints can change configuration. This allows the array to navigate sharp curves during installation and retrieval while maintaining robustness through the rigid body segments for rocky soil conditions.
Solution Approach 2:
The sensor array is contained within a protective hollow exoskeleton structure. The rigid bodies and flexible joints are nested within this protective casing, providing robustness for rocky soils while the overall flexible configuration allows retrieval through deformed pathways.
3Device complexity
If long gauge lengths are used to reduce the number of sensors and joints, then device complexity is reduced, but manufacturing precision becomes more difficult to maintain
Solution Approach 1:
The long array is segmented into multiple rigid bodies of manageable lengths connected by flexible joints. This segmentation maintains manufacturing precision by keeping individual components small and controllable, while the overall assembly achieves long gauge length to reduce total component count.
Solution Approach 2:
The flexible joints provide parameter changes in the form of angular flexibility, allowing each rigid body segment to be manufactured with standard precision while the joint flexibility compensates for cumulative alignment errors over long distances.
4Measurement precision
If azimuthal alignment is physically controlled during manufacture using grooves in casing, then measurement precision is improved, but ease of operation deteriorates due to difficulty of installation and grooved casing requirements
Solution Approach 1:
The mechanical groove-and-wheel alignment system is replaced with a calibration-based approach. Instead of physical constraints during installation, the array undergoes azimuth calibration during manufacture, replacing complex mechanical alignment structures with simpler, more installable components.
Solution Approach 2:
Azimuth calibration is performed preliminarily during the manufacture process rather than during field installation. This preliminary action ensures measurement precision is established before deployment, eliminating the need for complex grooved casing and difficult field alignment operations.
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 bipartite sensor array achieves long gauge lengths, reduces sensor costs, enhances robustness, simplifies installation, and allows retrieval of the sensory array, providing accurate geotechnical measurements with improved durability and flexibility.
Implementation Method 1
Both conventional inclinometers and SAA rely on gravimetric measurement of tilt. Measurement of tilt amounts to determining the portion of the gravity vector acting upon a mass supported by springs in a reference frame, as the axis of the reference frame is tilted.
Data Source
AI summary
A bipartite sensor array comprising two portions capable of assembly into a single sensory system. A first portion includes rigid bodies connected by elongate flexures and fitted with gravimetric tilt sensors. The elongate flexures are capable of non-monotonic and non-constant bend in two degrees of freedom. A second portion includes rigid bodies connected by joints, contains the first portion. The second portion, which may be delivered and assembled separately from the first, provides rigidity and protection, enabling the first portion to have short rigid bodies and long connecting flexures, thereby reducing the number of sensors required. The bipartite sensor array is applicable to geotechnical measurements of soil and civil structures.