Foreign material detection device and foreign material detection method
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Solution Overview
Problem
Existing foreign substance detection methods, such as those using ultrasonic waves, face challenges in accurately detecting foreign substances with low acoustic impedance, like soft substances, due to reduced measurement accuracy and difficulty in differentiating spectral changes.
Innovation Solution
A foreign substance detection device utilizing an electromechanical conversion element, specifically a piezoelectric element, that measures impedance changes to detect foreign substances based on mass load variations, enabling high-accuracy detection regardless of acoustic impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasonic waves are used to detect foreign substances by receiving reflected waves, then the detection method can identify foreign substances, but the measurement accuracy is lowered when multiple reflections occur inside the pipe
Solution Approach 1:
The patent extracts the problematic multiple reflection paths by using a specific ultrasonic probe configuration that receives only the first reflection from the foreign substance boundary, excluding subsequent multiple reflections. This is achieved by positioning the probe to detect waves reflected at the pipe wall-foreign substance interface while filtering out waves that have undergone multiple internal reflections, thereby maintaining detection capability while improving measurement reliability
Solution Approach 2:
Instead of trying to eliminate foreign substances or their reflections, the patent inverts the approach by using the reflection characteristics themselves as the detection signal. The system measures the time and intensity of ultrasonic wave reflections from the foreign substance boundary, converting what would normally be considered interference (reflected waves) into useful detection information, thereby achieving both foreign substance identification and accurate thickness measurement
2Difficulty of detecting and measuring
If high-order harmonic spectrum strength is measured to detect foreign substances, then foreign substance detection is possible, but detection of foreign substances with low acoustic impedance becomes difficult
Solution Approach 1:
The patent changes the detection parameter from high-order harmonic spectrum strength to fundamental frequency reflection characteristics. By measuring the reflection coefficient and time of flight at the fundamental frequency rather than relying on high-order harmonics, the system can detect foreign substances with low acoustic impedance that would otherwise produce minimal spectral changes, thereby improving both detectability and measurement precision for soft or low-impedance materials
Solution Approach 2:
The system performs preliminary characterization of the pipe and foreign substance acoustic properties before detection, establishing baseline reflection coefficients and sound speeds. This preliminary action allows the detection system to compensate for low acoustic impedance variations by comparing against known references, enabling accurate detection of soft foreign substances that would otherwise be difficult to distinguish from the pipe wall or fluid
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 device achieves high measurement accuracy for detecting foreign substances, including those with low acoustic impedance, by effectively measuring impedance changes at resonance frequencies, thereby preventing pipe clogging and device failures.
Implementation Method 1
an electromechanical conversion element 4, specifically a piezoelectric element, that measures impedance changes to detect foreign substances based on mass load variations
Implementation Method 2
measuring a resonance frequency of the electromechanical conversion element 4; the impedance calculation unit 6d is configured to calculate the impedance on the basis of the phase difference, the resonance frequency
Data Source
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AI summary
Provided is a foreign substance detection device including: an electromechanical conversion element attached to a pipe and configured to convert electric energy to mechanical energy and convert mechanical energy to electric energy; and a foreign substance detection unit configured to measure impedance of the electromechanical conversion element to detect adhesion of a foreign substance inside the pipe. The foreign substance detection unit includes: a power source configured to supply power to the electromechanical conversion element to cause the electromechanical conversion element to vibrate; a voltage measurement unit configured to measure an element voltage applied to the electromechanical conversion element when power is supplied from the power source; a current measurement unit configured to measure an element current flowing through the electromechanical conversion element when power is supplied from the power source; an impedance calculation unit configured to calculate the impedance on the basis of the element voltage and the element current; and a detection unit configured to detect adhesion of a foreign substance inside the pipe on the basis of the impedance calculated by the impedance calculation unit.