Envelope pulsed ultrasonic distance measurement system based upon amplitude modulation and phase modulation.

Area of Science:

• Instrumentation and Measurement
• Ultrasonic Transduction

Background:

• Traditional ultrasonic distance measurement systems face errors from inertia delay and amplitude attenuation.
• Existing amplitude modulation (AM) and phase modulation (PM) techniques have limitations in reducing these errors.

Purpose of the Study:

• To develop a novel microcomputer-based ultrasonic distance measurement system with enhanced accuracy and resolution.
• To introduce an efficient algorithm combining AM and PM (APESW) to mitigate measurement errors.

Main Methods:

• The proposed system utilizes an amplitude and phase modulation envelope square wave form (APESW) for ultrasonic pulse-echo measurements.
• A phase inversion phenomenon in the receiver's waveform is exploited to identify the 'measurement pulse' for accurate time-of-flight (TOF) determination.
• A counter-technique computes phase shifts for TOF, and a complex programmable logic device manages data acquisition and processing.

Main Results:

• The APESW system achieves a distance resolution of 0.1% of the wavelength at 40 kHz.
• The system demonstrates a standard uncertainty of 0.2 mm within a measurement range of 50-500 mm.
• The implementation on a complex programmable logic device facilitates PC-based calibration and examination.

Conclusions:

• The APESW technique effectively reduces errors associated with inertia delay and amplitude attenuation in ultrasonic measurements.
• The developed system offers high resolution, low cost, narrow bandwidth requirements, and ease of implementation.
• This novel system provides a robust and accurate solution for ultrasonic distance measurement applications.