Seismic Vibrator Base Plate Stiffness and Accelerometer Placement
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Solution Overview
Problem
Seismic vibrators face challenges in accurately determining the ground force applied during seismic surveys due to vibration and flexure of the base plate, which distorts readings and limits the availability of free space for accurate acceleration measurements, leading to inconsistent energy transfer and non-repeatability of source signatures across different locations.
Innovation Solution
A seismic vibrator with a base plate of increased stiffness and a strategically located accelerometer on the base plate to accurately measure acceleration, combined with a hydraulic actuator and isolators to minimize interference from supporting components, allowing for more precise control and energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the base plate is made with standard stiffness, then the structure remains simple and lightweight, but vibration and flexure distort acceleration readings and reduce measurement precision
Solution Approach 1:
The base plate's stiffness parameter is increased by changing its structural properties (thickness, material, or reinforcement) to reduce vibration and flexure during operation, thereby improving the accuracy of acceleration measurements without compromising structural integrity
2Stability of the object's composition
If components are added to support the base plate, then structural stability improves, but the available free space for sensor placement decreases
Solution Approach 1:
Support components are positioned at the periphery or edges of the base plate, utilizing the outer dimensional space, thereby maintaining structural stability while preserving the central free space required for accelerometer placement and operation
3Measurement precision
If the accelerometer is placed on the base plate, then direct measurement of base plate acceleration is achieved, but vibration and flexure cause distorted readings
Solution Approach 1:
The base plate stiffness parameter is modified to reduce the magnitude of vibration and flexure during operation, thereby minimizing the distortion of acceleration readings while still allowing direct measurement capability
Solution Approach 2:
The stiffened base plate acts as an intermediary that transmits motion to the accelerometer while filtering out high-frequency vibrations and flexure, providing a more accurate representation of the actual ground force
4Measurement precision
If the base plate stiffness is increased, then vibration and flexure are reduced improving measurement accuracy, but manufacturing complexity and cost increase
Solution Approach 1:
The base plate stiffness is increased through optimized structural parameters such as thickness, material selection, or geometric reinforcement that balance the need for reduced vibration with manufacturing feasibility and cost considerations
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 enhances the accuracy of ground force computation and energy transfer, resulting in more reliable seismic data and improved repeatability of seismic source signatures across different locations, as evidenced by improved power spectra and phase matching with actual ground forces.
Implementation Method 1
a first sensor is disposed directly on the base plate and detects first signals indicative of acceleration imparted to the base plate
Implementation Method 2
The moving reaction mass acts upon the base plate to impart a seismic source signal into the earth
Data Source
Figure 1A~1B
Figure 1C~2
Figure 3A~3C
AI summary
A seismic vibrator has a base plate with at least four isolators isolating a frame from the base plate. Each of these isolators is offset from the plate's footprint on shelves to free up area on the plate's top surface. An accelerometer disposed directly on the base plate detects the acceleration imparted to the plate. To reduce flexing and bending, the plate has an increased stiffness and approximately the same mass of a plate for a comparably rated vibrator. The accelerometer disposes at a particular location of the plate that experiences transition between longitudinal flexing along the plate's length. This transition location better represents the actual acceleration of the plate during vibration and avoids overly increased and decreased acceleration readings that would be obtained from other locations on the plate.