Acoustic Doppler Vibrometer With Stabilized Platform
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Solution Overview
Problem
Existing sensors for detecting surface vibrations face challenges such as altered response due to coupled mass, inefficient deployment, high cost, bulkiness, sensitivity to surface roughness, and instability, particularly in seismic exploration where large numbers of sensors are required.
Innovation Solution
An uncoupled acoustic Doppler vibrometer with a stabilized platform and transducers mounted on a damped mass-spring system, allowing for accurate Doppler shift measurements without surface coupling, featuring a relative motion compensator to reduce noise and a wide dynamic range amplifier for high sensitivity and low noise levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If coupled sensors (geophones or accelerometers) are used for seismic exploration, then the deployment and retrieval of large numbers of sensors is very inefficient and costly, but the sensors can detect vibrations effectively
Solution Approach 1:
The patent replaces coupled mechanical sensors with uncoupled acoustic sensors that use acoustic waves instead of mechanical contact. This substitution eliminates the need for physical coupling to the ground, allowing sensors to be deployed without individual placement, thereby dramatically improving deployment efficiency and reducing time loss.
2Reliability
If coupled sensors are used, then the response of the vibrating structure is altered by the coupled mass of the sensors, but the sensors provide good earth-to-transducer coupling
Solution Approach 1:
The patent extracts the transducer from direct mechanical coupling with the ground, using acoustic waves to sense vibrations without physical contact. This removes the coupled mass that alters the vibrating structure's response while maintaining measurement capability through acoustic coupling, thereby preserving response accuracy.
3Measurement precision
If optical sensors (LDV) are used for uncoupled measurement, then the resolution can be as high as a few nanometers, but the devices are bulky, expensive, and very sensitive to surface roughness
Solution Approach 1:
The patent substitutes optical LDV systems with acoustic sensors that use sound waves instead of light. This replacement maintains high resolution capability while significantly reducing device complexity, bulkiness, and cost, making the system more practical for field deployment.
4Measurement precision
If uncoupled sensors are mounted on an ultra-stable platform, then the sensor movement is minimized to reduce measurement errors, but the platform is either too cumbersome or very expensive to implement in the field
Solution Approach 1:
The patent replaces the need for ultra-stable mechanical platforms by using acoustic waves that are inherently less sensitive to sensor movement. The acoustic measurement principle allows for acceptable measurement accuracy without requiring cumbersome or expensive stabilization platforms, thereby reducing device 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 provides high-resolution, cost-effective, and durable sensors suitable for large-scale deployment, capable of measuring low-frequency seismic waves with reduced sensitivity to surface roughness and ambient noise, enabling efficient seismic data acquisition.
Implementation Method 1
a transmitter transducer and a receiver transducer mounted on the moveable mass, the transmitter transducer arranged to transmit an acoustic wave towards the surface, and the receiver transducer arranged to receive a reflected wave from the surface
Implementation Method 2
a detector that measures motion of the surface based on a Doppler shift in the reflected wave
Implementation Method 3
a stabilised platform comprising a support structure and a moveable mass resiliently suspended with respect to the support structure
Data Source
AI summary
An apparatus for sensing motion of a surface comprises a stabilized platform comprising a support structure and a moveable mass resiliently suspended with respect to the support structure; a transmitter transducer and a receiver transducer mounted on the moveable mass, the transmitter transducer arranged to transmit an acoustic wave towards the surface, and the receiver transducer arranged to receive a reflected wave from the surface, and detection means for measuring motion of the surface based on a Doppler shift in the reflected wave. The detection means may comprise an amplifier arranged to receive a Doppler modulated signal from the receiver transducer, and a phase detector arranged to receive an amplified signal from the amplifier and to provide a demodulated output signal indicative of the motion of the surface. Preferably, the apparatus further comprises relative motion compensation means arranged to remove from the demodulated output signal phase noise caused by motion of the transducers, and to provide a surface motion output signal.