Ultrasonic Wave Propagation Time Measuring System Using Correlation
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Solution Overview
Problem
Conventional ultrasonic wave position detection systems using piezoelectric or magnetostrictive elements face challenges in miniaturization, high power consumption, and difficulty in transmitting modulated waves due to residual vibrations and low transmission gain, especially in small-sized movable objects like electronic pens, which affects accurate propagation time measurement and is affected by reflected waves.
Innovation Solution
An ultrasonic wave propagation time measuring system that employs an electromagnetic wave transmission unit, a piezoelectric or magnetostrictive element-driven ultrasonic wave transmission unit, and a data processing unit that uses pseudo-random signal modulation and correlation computation to isolate direct wave propagation time, reducing the impact of residual vibrations and reflected waves, and operates within a narrow band for efficient and accurate position detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a piezoelectric element driven by voltage is used as an ultrasonic wave generation source, then power consumption is low, but transmission gain is insufficient and residual vibration is prolonged
Solution Approach 1:
The patent uses periodic pulse signals to drive the piezoelectric element, transmitting ultrasonic waves in discrete bursts rather than continuously. This periodic excitation allows the system to achieve adequate transmission gain during each pulse while allowing residual vibrations to decay between pulses, thus resolving the contradiction between power consumption and transmission effectiveness
Solution Approach 2:
The patent dynamically adjusts the driving conditions of the piezoelectric element by using variable pulse widths and frequencies adapted to the specific measurement scenario. This dynamic control optimizes the balance between power consumption and transmission gain, enabling adequate ultrasonic wave transmission while minimizing residual vibration effects
2Stability of the object's composition
If a resonance phenomenon is used to transmit ultrasonic wave at constant phase, frequency and gain, then transmission is stable, but transmission gain at other frequencies is quite low and various modulation methods cannot be used
Solution Approach 1:
The patent changes the driving parameters of the piezoelectric element dynamically, using variable frequency and amplitude modulation to achieve both stable transmission at the resonant frequency and the capability to adapt to different measurement requirements. The system maintains stability through feedback control while enabling modulation through parameter variation
3Productivity
If a single or burst ultrasonic wave signal is transmitted at a fixed period for continuous propagation time measurement, then measurement can be performed continuously, but an audible sound is generated that should be eliminated
Solution Approach 1:
The patent uses periodic ultrasonic wave transmission with carefully selected pulse widths and intervals. By controlling the duty cycle and frequency of the periodic signals to remain above the human audible range (>20 kHz), the system achieves continuous measurement capability without generating perceptible audible sounds
Solution Approach 2:
The patent converts the potential harmful effect of audible sound generation into a benefit by using ultrasonic frequencies that are imperceptible to humans. The same periodic transmission mechanism that enables continuous measurement also ensures the generated sounds are in the ultrasonic range, thus eliminating the harmful audible effect while maintaining measurement continuity
4Measurement precision
If reflected waves are present in the ultrasonic wave signal, then propagation time measurement is affected, but eliminating reflected waves is difficult
Solution Approach 1:
The patent extracts the direct wave signal from the composite signal containing both direct and reflected waves. By using correlation processing with a reference signal, the system isolates the direct wave component and eliminates the influence of reflected waves on propagation time measurement
Solution Approach 2:
The patent introduces a correlation function as an intermediary processing step between signal reception and propagation time calculation. This intermediary operation separates the direct wave signal from reflected waves by comparing the received signal with a known transmitted signal pattern, thus enabling accurate measurement despite the presence of reflections
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
Enables accurate and high-speed ultrasonic wave propagation time measurement with low power consumption and cost, effectively eliminating the effects of residual vibrations and reflected waves, and supports compact implementation in small-sized movable objects.
Implementation Method 1
an ultrasonic wave transmission unit that is driven by the ultrasonic wave drive signal and formed from a piezoelectric or magnetostrictive element for transmitting an ultrasonic wave signal
Implementation Method 2
an ultrasonic wave transmission unit that is driven by the ultrasonic wave drive signal and formed from a piezoelectric or magnetostrictive element
Implementation Method 3
a data processing unit, having a waveform the same as the ultrasonic wave drive signal as a model waveform, that computes correlation values between the detected ultrasonic wave signal and the model waveform, detects a main peak value of the computed correlation values
Data Source
AI summary
A position detection method and system that eliminate an effect of residual vibration of a piezoelectric or magnetostrictive element, increase correlativity between a received ultrasonic waveform and a model waveform, and are not affected by a reflected wave of an ultrasonic wave signal. A transmission unit of an ultrasonic wave propagation time measuring system of the present invention generates an electromagnetic wave signal including a trigger signal that indicates transmission timing and an ultrasonic wave drive signal by modulating an ultrasonic wave on the basis of a pseudo-random signal with high autocorrelativity at the same time as transmission of the electromagnetic wave signal, and transmits an ultrasonic wave signal of a frequency higher than a frequency of the ultrasonic wave drive signal by an ultrasonic wave transmitter. A reception unit detects the electromagnetic wave signal and the ultrasonic wave signal, and is provided with a data processing circuit for computing, with the ultrasonic wave drive signal as a model waveform, correlation values between the detected ultrasonic wave signal and the model waveform, detecting a main peak value of the computed correlation values, and computing an ultrasonic wave propagation time from a point in time of detection of the electromagnetic wave signal and a point in time of detection of the main peak value.