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

Abstract

A novel microcomputer-based ultrasonic distance measurement system is presented. This study proposes an efficient algorithm which combines both the amplitude modulation (AM) and the phase modulation (PM) of the pulse-echo technique. The proposed system can reduce error caused by inertia delay and amplitude attenuation effect when using the AM and PM envelope square wave form (APESW). The APESW ultrasonic driving wave form causes a phase inversion phenomenon in the relative wave form of the receiver. The phase inversion phenomenon sufficiently identifies the "measurement pulse" in the received wave forms, which can be used for accurate time-of-flight (TOF) measurement. In addition, combining a countertechnique to compute the phase shifts of the last cycle for TOF, the presented system can obtain distance resolution of 0.1% of the wavelength corresponding to the 40 kHz frequency of the ultrasonic wave. The standard uncertainty of the proposed distance measurement system is found to be 0.2 mm at a range of 50-500 mm. The APESW signal generator and phase detector of this measuring system are designed on a complex programmable logic device, which is used to govern the TOF measurement and send the data to a personal computer for distance calibration and examination. The main advantages of this APESW system are high resolution, low cost, narrow bandwidth requirement, and ease of implementation.

Development of an Ultrasound Based Tracking System for Indoor Robot Localization

“…The controllers of the anchors receive this command through their interrupt inputs and transmit the Manchester Development of an ultrasound based tracking system for indoor robot localization 157 modulated infrared packet (IR) containing the robot ID for the ultrasonic receiver node placed on the robot. If the node recognizes its own ID, it responds with a phase-modulated ultrasonic (US) chirp signal [6]. Simultaneously the controllers of the anchors start to sample the ultrasonic receiver.…”

“…We implemented a distance measurement method based on amplitude and phase modulation similarly as in the study [6], see Fig. 2.…”

Robust High-Accuracy Ultrasonic Range Measurement System

“…This technique uses a frequency change detector to estimate the Time of Flight and refine the estimate by adding the phase shift measured by a digital phase meter. Amplitude change and phase inversion detection and phase shift using Amplitude Modulation and Phase Modulation Envelope Square Wave form (APESW) was proposed in [17], [18], [19]. This technique is quite similar to that proposed in [16] except that an amplitude and phase change detector is used for Time of Flight estimation instead of a frequency change detector.…”

“…Many ultrasonic range measurement methods have been proposed in the literature [12][13][14][15][16][17][18][19]. Time of Flight (TOF) and phase shift methods are used in most ultrasonic range measurement systems.…”

“…The phase shift method is typically more accurate than the cross-correlation based TOF method. However, with the phase shift method, the maximum range that can be estimated is limited to one wavelength of the transmitted signal [15,17]. This paper proposes a novel method for ultrasonic range estimation.…”