Time Reversal Pulse Position Modulation for Guided Elastic Wave Data Communication
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional communication schemes for structural health monitoring applications, such as those using electromagnetic or acoustical waves, are ineffective for buried underground pipes or hollow sub-sea structures due to signal decay in soil or water, leading to unreliable data transmission and high costs.
Innovation Solution
A time reversal based data communication method utilizing guided elastic waves and piezoelectric sensors embedded in steel pipes or similar structures, which employs pulse position modulation to overcome channel dispersion and achieve accurate timing acquisition and synchronization, enabling reliable data transmission even in dispersive environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromagnetic or acoustical waves are used for data communication in buried pipes or sub-sea structures, then communication can be established, but signal decay occurs in soil or water resulting in very short transmission range and unreliable data transmission
Solution Approach 1:
The patent introduces steel pipes as an intermediary transmission medium between the sensor nodes and the surface. Instead of transmitting electromagnetic or acoustical waves directly through soil or water, the system uses guided elastic waves that propagate through the steel pipe structure, which serves as a protective and efficient transmission channel that overcomes the signal decay problem in soil or water environments
Solution Approach 2:
The patent replaces electromagnetic wave transmission with mechanical elastic wave transmission through the steel pipe structure. By using guided elastic waves that travel through the solid pipe wall, the system achieves reliable long-distance communication without the signal decay issues associated with electromagnetic waves in soil or water
2Productivity
If guided elastic waves are used for data communication, then long distance transmission is achieved, but multi-modal and dispersive characteristics make it difficult to interpret channel responses and transfer structural information data correctly
Solution Approach 1:
The patent applies time reversal processing to the received dispersive signals to compensate for channel effects before interpretation. By reversing the time domain signal, the system pre-compensates for the multi-modal and dispersive characteristics of the guided waves, making the channel responses easier to interpret and the structural information more reliable
Solution Approach 2:
The patent changes the time domain parameters of the received signals by applying time reversal processing. This transformation converts the dispersed, multi-modal channel responses into focused, interpretable signals, effectively changing the temporal characteristics to overcome the complexity of channel interpretation
3Measurement precision
If time reversal pulse position modulation is used, then signal energy is focused over dispersive channel resulting in clean signals for demodulation, but timing acquisition and synchronization become critical
Solution Approach 1:
The patent implements a feedback mechanism where the receiver detects the focused signal peaks and uses this timing information to synchronize with the transmitted data. The time reversal process creates distinct, focused peaks that provide clear feedback for timing acquisition, enabling the receiver to accurately determine symbol boundaries and achieve synchronization
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
This method allows for high data rate communication with low complexity and cost, effectively compensating for signal dispersion and multipath interference, ensuring reliable data transmission and structural health monitoring in challenging environments.
Implementation Method 1
Piezoelectric sensors have long been used for inspecting the integrity of large civil structures such as pipes, offshore platforms, bridges, railways, etc. Upon excitation, active acoustic sensor, or actuators, can generate elastic waves that propagate a long distance
Implementation Method 2
The time reversal based pulse position modulation (PPM) method can successfully take advantage of the multipath and multimodal dispersion, focus signal energy over dispersive channel, thus resulting in clean signals for demodulation
Implementation Method 3
modulating the time reversed signal using pulse position modulation to generate a time reversed pulse position modulated signal
Data Source
AI summary
Embedded piezoelectric sensors in large civil structures for structural health monitoring applications require data communication capabilities to effectively transmit information regarding the structure's integrity between sensor nodes and to the central processing unit. Conventional communication modalities include electromagnetic waves or acoustical waves. While guided elastic waves can propagate over long distances on solid structures, their multi-modal and dispersive characteristics make it difficult to interpret the channel responses and to transfer useful information along pipes. Time reversal is an adaptive transmission method that can improve the spatiotemporal wave focusing. The present disclosure presents the basic principles of a time reversal based pulse position modulation (TR-PPM) method and demonstrates TR-PPM data communication by simulation. The present disclosure also experimentally demonstrates data communication with TR-PPM on pipes. Simulated and experimental results demonstrate that TR-PPM for data communications can be achieved successfully using guided elastic waves.