Ultrasonic Ranging Research Articles

Design of the Ultrasonic Ranging System based on the Internet of Things

Design of the Ultrasonic Ranging System based on the Internet of Things

Non-contact Ultrasonic Sonar-based Ranging Technique for In-motion 3D Railroad Tie Deflection Measurements

This paper presents an ultrasonic technique for non-contact surface deflection mapping of railroad ties using concepts of sonar-based ranging. The technique utilizes an array of capacitive ultrasonic transducers arranged along the length of the railroad tie at a lift-off distance of 3 in. from the rail surface to ensure contactless measurements. The transducer array is used in pulse-echo mode and distances from the transducers to the tie surface are measured by tracking the time-of-flight of the waves reflected from the tie surface. A reference-based cross-correlation operation is introduced to compute the time-of-flight, wherein one of the transducers is used as a reference for the distance measurements. The reference-based cross-correlation ensures accurate peak-detection for time-of-flight based differential distance measurements. An acoustic signal strength-based technique is utilized to differentiate between signals reflected from ties and those reflected from ballast. Laboratory scale tests were first performed as a proof-of-concept on a slender wooden beam to measure deflections in loaded and unloaded conditions. Dynamic tests were also performed on this beam to determine the ability to track time-varying positions. Field tests on a replica test track with wood ties were performed at the Rail Defect Testing Facility at University of California San Diego by mounting the prototype on a test-cart moved at walking speed. A dynamic assessment of the prototype was also performed to determine natural frequencies of the mounting beam that may be relevant for future uses at higher speeds. The results indicate the potential of this non-contact system to measure full-field tie deflections in 3D in-motion. This ability may potentially be used to detect conditions of poor tie support that may cause derailments.

Railroad Sleeper Condition Monitoring Using Non-Contact in Motion Ultrasonic Ranging and Machine Learning-Based Image Processing.

An ultrasonic sonar-based ranging technique is introduced for measuring full-field railroad crosstie (sleeper) deflections. Tie deflection measurements have numerous applications, such as detecting degrading ballast support conditions and evaluating sleeper or track stiffness. The proposed technique utilizes an array of air-coupled ultrasonic transducers oriented parallel to the tie, capable of "in-motion" contactless inspections. The transducers are used in pulse-echo mode, and the distance between the transducer and the tie surface is computed by tracking the time-of-flight of the reflected waveforms from the tie surface. An adaptive, reference-based cross-correlation operation is used to compute the relative tie deflections. Multiple measurements along the width of the tie allow the measurement of twisting deformations and longitudinal deflections (3D deflections). Computer vision-based image classification techniques are also utilized for demarcating tie boundaries and tracking the spatial location of measurements along the direction of train movement. Results from field tests, conducted at walking speed at a BNSF train yard in San Diego, CA, with a loaded train car are presented. The tie deflection accuracy and repeatability analyses indicate the potential of the technique to extract full-field tie deflections in a non-contact manner. Further developments are needed to enable measurements at higher speeds.

A Robust Foot-Mounted Positioning System Based on Dual IMU Data and Ultrasonic Ranging

Foot-mounted positioning system (FPS) is regarded as an important application for GPS-denied scenes, including but not limited to emergency rescue, medical health, and individual soldier positioning. With the assistance of zero-velocity update technology (ZUPT), the basic positioning function can be realized, while the largest problem is that the accumulation of systematic heading drift and positioning error cannot be completely constrained. This article presents a robust FPS based on dual inertial measurement unit data and ultrasonic ranging (FPS-DU). Bidirectional long short-term memory (Bi-LSTM) network is developed for the recognition of quasi-static (QS) period for the performance enhancement of ZUPT, and multilevel constraints are modeled for decreasing the cumulative error of the single foot-mounted model. In addition, a unified Kalman-based location estimator is developed combining dual foot-mounted inertial data and sphere constraint-based ultrasonic ranging results, enhanced by a robust ultrasonic outlier detector. Comprehensive experiments demonstrate that the proposed FPS-DU realizes much more accurate and robust positioning accuracy (between 0.371% and 0.548% under different test environments and traveled distances) compared with traditional single FPSs (S-FPSs).

Modified FMCW Scheme for Improved Ultrasonic Positioning and Ranging of Unmanned Ground Vehicles at Distances < 50 mm

Unmanned ground vehicles (UGVs) find extensive use in various applications, including that within industrial environments. Efforts have been made to develop cheap, portable, and light-ranging/positioning systems to accurately locate their absolute/relative position and to automatically avoid potential obstacles and/or collisions with other drones. To this aim, a promising solution is the use of ultrasonic systems, which can be set up on UGVs and can potentially output a precise reconstruction of the drone's surroundings. In this framework, a so-called frequency-modulated continuous wave (FMCW) scheme is widely employed as a distance estimator. However, this technique suffers from low repeatability and accuracy at ranges of less than 50 mm when used in combination with low-resource hardware and commercial narrowband transducers, which is a distance range of the utmost importance to avoid potential collisions and/or imaging UGV surroundings. We hereby propose a modified FMCW-based scheme using an ad hoc time-shift of the reference signal. This was shown to improve performance at ranges below 50 mm while leaving the signal unaltered at greater distances. The capabilities of the modified FMCW were evaluated numerically and experimentally. A dramatic enhancement in performance was found for the proposed FMCW with respect to its standard counterpart, which is very close to that of the correlation approach. This work paves the way for the future use of FMCWs in applications requiring high precision.

Blind Person Verification Using Temperature Compensated Ultrasonic Ranging

Blind Person Verification Using Temperature Compensated Ultrasonic Ranging

Flow fields around tandem and staggered piers on a mobile bed

An experimental investigation on flow fields within the scour holes upstream and downstream of circular piers positioned in tandem and staggered arrangements is reported and compared with isolated piers on mobile beds with uniform sediment. The instantaneous bed elevations and instantaneous three dimensional (3D) velocities were measured using a 5 MHz Ultrasonic Ranging system and 16 MHz micro down looking acoustic Doppler velocimeter, respectively. The velocity and flow depth were measured at different locations under near equilibrium bed scour conditions. The measured 3D velocities were processed for the computation of flow parameters, such as velocity fields, streamline patterns, vorticity fields, and circulation. Furthermore, turbulence intensities, turbulent kinetic energy, Reynolds shear stresses, and bed shear stresses around the piers for all three pier configurations were computed from the detrended velocity signals to identify significant differences in the flow parameters and turbulence in the tandem and staggered pier arrangements as compared to those for an isolated pier. A recirculation zone was found near the bed in front of the rear pier in the tandem case from the streamline patterns. The vortices in the bi-vortex system were observed to be opposite to each other in the gap between the three piers in the staggered case. A strong secondary vortex also was observed apart from the primary vortex at the foot of the pier (θ = 0°) in all the three configurations. The strength of the horseshoe vortex (combination of primary and secondary vortices) was found to be higher at the front piers of the staggered arrangement as compared to those of the tandem piers, followed by the isolated pier. The bed shear stresses were found to be higher for the staggered piers than for the tandem piers in the direction of flow (θ = 0°). However, a 50% reduction in the bed shear stresses was observed behind the tandem piers at θ = 180°. The study reported in this paper provides the foundation for further investigation of countermeasures against local scour around tandem and staggered bridge piers on a mobile bed with non-uniform sediment.

Improved Measurement Accuracy Based on Moving Sine-Wave Fitting for Ultrasonic Ranging

In ultrasonic ranging system, the time-of-flight (TOF), which acquired by the determination of two special points of ultrasonic echo, is important for accuracy and speed. The published calculation of TOF processing methods is too enormous to affect the real-time performance. To improve its measurement accuracy and speed, we proposed a new algorithm called “moving sine-wave fitting” to calculate the envelope of ultrasonic echo for each calibration point. Then, the absolute feature point (AFP) corresponding to half of the envelope peak can be defined and used to find out the relative feature point (RFP); the linear relationship between the RFPs and the known distances should be obtained referring to calibration points. At last, the distance on the measure can be acquired by using linear interpolation according to the above relationship. The measurement experiments have been performed on a set of distances, which shows a good measurement resolution that the overall measurement accuracy is 0.513 mm, and the linear correlation coefficient between the RFPs and the obtained distances is R2 = 0.806.

Review of Ultrasonic Ranging Methods and Their Current Challenges.

Ultrasonic ranging has been widely used in automobiles, unmanned aerial vehicles (UAVs), robots and other fields. With the appearance of micromachined ultrasonic transducers (MUTs), the application of ultrasonic ranging technology presents a more extensive trend. This review focuses on ultrasonic ranging technology and its development history and future trend. Going through the state-of-the-art ultrasonic ranging methods, this paper covers the principles of each method, the signal processing methodologies, the overall system performance as well as key ultrasonic transducer parameters. Moreover, the error sources and compensation methods of ultrasonic ranging systems are discussed. This review aims to give an overview of the ultrasonic ranging technology including its current development and challenges.

Development and Realization of an Ultrasonic Ranging Detection and Tracking Device

There are several ways of contactless distance measurements. This research work made use of the principle of ultrasonic distance measurements and calculations as well as tracking of dynamic object by the techniques of distance comparison. When an electrical pulse of high voltage is applied to the ultrasonic transducer it vibrates across a specific spectrum of frequencies and generates a burst of sound waves. Each time any obstacle comes ahead of the ultrasonic sensor, the sound waves will reflect in the form of echo and generates an electric pulse. The time taken between sending sound waves and receiving the echo was calculated and the patterns of echo were compared with the patterns of sound waves to determine the detected signals condition. The device consists of two HC-SR04 ultrasonic sensors that sweep continuously through 1800 to detect and track object based on developed and installed codes in the Arduino Uno microcontroller and displays the range and angular position using Processing 3 Software on a computer screen display. The envisaged minimum and maximum range of object detections is 2cm and 39cm respectively using processed signal. However, the measured distance is from 5cm to 35cm and the corresponding calculated distances using waveforms from an oscilloscope were 6.8cm and 47.6cm. The discrepancies were attributable to the 0.2ms rise time of the trigger signals. The device was capable of tracking only relatively slow-moving objects and can be applicable in robotic vision, automatic guided vehicles, security surveillance, automobile anti-collision system and precision contactless measurements.

Acoustic Simulation for Performance Evaluation of Ultrasonic Ranging Systems

The recent growing interest in indoor positioning applications has paved the way for the development of new and more accurate positioning techniques. The envisioned applications, include people and asset tracking, indoor navigation, as well as other emerging market applications, require fast and precise positioning. To this end, the effectiveness and high accuracy and refresh rate of positioning systems based on ultrasonic signals have been already demonstrated. Typically, positioning is obtained by combining multiple ranging. In this work, it is shown that the performance of a given ultrasonic airborne ranging technique can be thoroughly analyzed using renowned academic acoustic simulation software, originally conceived for the simulation of echographic transducers and systems. Here, in order to show that the acoustic simulation software can be profitably applied to ranging systems in air, an example is provided. Simulations are performed for a typical ultrasonic chirp, from an ultrasound emitter, in a typical office room. The ranging performances are evaluated, including the effects of acoustic diffraction and air frequency dependent absorption, when the signal-to-noise ratio (SNR) decreases from 30 to −20 dB. The ranging error, computed over a point grid in the space, and the ranging cumulative error distribution is shown for different SNR levels. The proposed approach allowed us to estimate a ranging error of about 0.34 mm when the SNR is greater than 0 dB. For SNR levels down to −10 dB, the cumulative error distribution shows an error below 5 mm, while for lower SNR, the error can be unlimited.

A Novel Ultrasonic TOF Ranging System Using AlN Based PMUTs.

This paper presents a high-accuracy complementary metal oxide semiconductor (CMOS) driven ultrasonic ranging system based on air coupled aluminum nitride (AlN) based piezoelectric micromachined ultrasonic transducers (PMUTs) using time of flight (TOF). The mode shape and the time-frequency characteristics of PMUTs are simulated and analyzed. Two pieces of PMUTs with a frequency of 97 kHz and 96 kHz are applied. One is used to transmit and the other is used to receive ultrasonic waves. The Time to Digital Converter circuit (TDC), correlating the clock frequency with sound velocity, is utilized for range finding via TOF calculated from the system clock cycle. An application specific integrated circuit (ASIC) chip is designed and fabricated on a 0.18 μm CMOS process to acquire data from the PMUT. Compared to state of the art, the developed ranging system features a wide range and high accuracy, which allows to measure the range of 50 cm with an average error of 0.63 mm. AlN based PMUT is a promising candidate for an integrated portable ranging system.

Design of ACC Adaptive Cruise System Based on Ultrasonic Ranging and Internet of Vehicles

Nowadays, with the development of society, the vehicle ownership continues to increase. Vehicle has become the third important space for people besides home and office. As an important means of transportation for daily travel, people pay more and more attention to the convenience and safety of vehicle control. However, most vehicles sold on the market today are not equipped with emergency braking or emergency avoidance systems, even if equipped with the system, its accuracy is not high enough. When an emergency situation occurs in front of the vehicle, the vehicle cannot evade or brake on its own, only the driver can take measures, which often causes unnecessary collision. An ACC adaptive cruise system using ultrasonic ranging and Internet of Vehicles can share driving information between vehicles via Bluetooth to ensure identification of the speed and accuracy of the front vehicle, and able to avoid the front vehicle without driver’s intervention, enhancing emergency response capabilities. At the same time, unlike the existing ACC adaptive cruise system, most of which can only be activated when the speed is higher than 25km/h or 30km/h. This system can work at full speed of the vehicle, automatically follow the front vehicle, and automatically brake or accelerate reverse, increasing the convenience of daily driving.

Formation and migration of ripple pattern due to pure wave

ABSTRACT This paper reports an experimental study carried out in a laboratory flume to study the ripple formation and migration for three different sediment sizes ranging from fine sand to coarse sand under the influence of surface waves of different frequencies. This study compares the ripple length, height, ripple patch formation and migration characteristics for different wave frequencies and sediment sizes. Three-dimensional velocity was measured by 3D micro-ADV (Acoustic Doppler Velocimeter) and the evolution of bed morphology was quantified by Ultrasonic Ranging System (URS), SeaTek Inc. It is found from experimental results that patches (bunch of ripples) do not appear all over the bed at a time, rather these patches appear at isolated locations and the separation between the patches scale with the wave length of surface waves. Further, the ripple migration rate is evaluated and its relationship with sediment grain size and frequency is presented.

Doppler Correction in Moving Narrowband Ultrasonic Ranging Sensors for Small-Scale Motion Tracking

Narrowband ultrasonic sensors can be used for motion tracking and small-scale localization. Moving sensor nodes emitting ultrasonic waves produce a Doppler shift in the received signals. Doppler correction methods in narrowband ultrasonic motion tracking systems are explained in this letter. Two methods are suggested for Doppler compensation for small-scale localization using ultrasonic sensors. One of the methods requires a pilot carrier to be added to the transmitted signal and the other method exploits range-Doppler coupling for Doppler correction. In the simulation experiments, we compare the performance of the two methods with the traditional methods. We implement both the methods on hardware and compare the performance of the methods for ranging and localization in the presence of Doppler shift.

Cohesive river bank erosion mechanism under wave-current interaction: A flume study

The effect of hydrodynamic forces due to combined action of surface waves and current on the riverbank is critical to understand sediment entrainment, transport and bank line retreatment process. In understanding the temporal effect of turbulent structures under induced wave-current flow, a series of laboratory experiments were carried out. Micro-Acoustic Doppler Velocimeter (ADV) and Ultrasonic Ranging System (URS) were used simultaneously for the measurement of velocity fluctuations and bank undercut depth increment. Modulation of the turbulent flow characteristics and the benefaction of turbulent bursting structures at the initiation of erosion process and before the failure of the cohesive bank due to undercut progression are discussed. The results show that velocity and Reynolds shear stress have direct dependence on the size and rate of the entrainment of cohesive aggregates from bank face. The effect of wave-current motion leads to an increase in shear stress at the lateral bank giving rise to erosion and transportation of sediment particles/aggregates. Quadrant analysis of the random velocity fluctuation under wave-current flow at the initiation of erosion process shows strong presence of ejection and sweep events. Findings from the present study may provide a better understanding on the design of cohesive bank erosion control measures.

A Crop Canopy Localization Method Based on Ultrasonic Ranging and Iterative Self-Organizing Data Analysis Technique Algorithm.

To protect crops from diseases and increase yields, chemical agents are applied by boom sprayers. To achieve the optimal effect, the boom and the crop canopy should be kept at an appropriate distance. So, it is crucial to be able to distinguish the crop canopy from other plant leaves. Based on ultrasonic ranging, this paper adopts the fuzzy iterative self-organizing data analysis technique algorithm to identify the canopy location. According to the structural characteristics of the crop canopy, based on fuzzy clustering, the algorithm can dynamically adjust the number and center of clusters so as to get the optimal results. Therefore, the distances from the sensor to the canopy or the ground can be accurately acquired, and the influence of lower leaves on the measurement results can be alleviated. Potted corn plants from the 3-leaf stage to the 6-leaf stage were tested on an experiment bench. The results showed that the calculated distances from the sensor to the canopy using this method had good correlation with the manually measured distances. The maximum error of calculated values appeared at the 3-leaf stage. With the growth of plants, the error of calculated values decreased. The increased sensor moving speeds led to increased error due to the reduced data points. From the 3-leaf stage to the 5-leaf stage, the distances from the sensor to the ground can also be obtained at the same time. The method proposed in this paper provides a practical resolution to localize the canopy for adjusting the height of sprayer boom.

A High-Resolution Ultrasonic Ranging System Using Laser Sensing and a Cross-Correlation Method

Ultrasound has been proven to be a valid tool for ranging, especially in water. In this paper, we design a high-resolution ultrasonic ranging system that uses a thin laser beam as an ultrasonic sensor. The laser sensing provides a noncontact method for ultrasound detection based on acousto-optic diffraction. Unlike conventional methods, the ultrasound transmitted from the transducer is recorded as the reference signal when it first passes through the laser. It can be used to improve the accuracy and resolution of the time-of-flight (TOF) by a cross-correlation method. Transducers with a central frequency of 1 MHz and diameters of 20 mm and 28 mm are used in the experiment. Five targets and a test piece are used to evaluate the ranging performance. The sound velocity is measured by the sound velocity profiler (SVP). The repeatability error of TOF is less than 4 ns, and the theoretical resolution of TOF is 0.4 ns. The results show a measurement resolution within one-tenth of the wavelength of ultrasound and an accuracy better than 0.3 mm for targets at a distance up to 0.8 m. The proposed system has potential applications in underwater ranging and thickness detection.

Application of Ultrasonic Sensors in the Vehicle Collision Avoidance and Early Warning System

In order to improve the vehicle safety performance, the ultrasonic range finder is applied to the development of an automatic brake system. In a low-speed driving or reversing motion, the ultrasonic sensors can detect whether there are obstacles at front or back of the vehicle, optimize the ranging algorithm and build up a collision avoidance model. The temperature sensor can be used to measure the ambient temperature in real-time manner, correct the ultrasonic ranging result, display the distance between vehicle and obstacle and warn of the driver, and in case of emergency, automatically control the vehicle to start the emergency brake device. The ultrasonic collision avoidance and early warning system based on the microcontroller can help the driver have a good knowledge of the surrounding conditions of the vehicle and thus being of great significance for ensuring driving safety.

Transformerless Ultrasonic Ranging System with the Feature of Intrinsic Safety for Explosive Environment.

The transformer used in the conventional ultrasonic ranging system could provide a huge instantaneous driving voltage for the generation of ultrasonic wave, which leads to the safety problem in the explosive mixture. This paper proposes a transformerless ultrasonic ranging system powered by the intrinsically safe power source and analog switches. The analysis of intrinsic characteristics of ultrasonic driving circuit is realized in normal and fault conditions. The echo-processing circuit combined with LIN bus technology is further adopted in order to improve the system stability. After the analysis of the timing diagram of ranging instruction, the evaluation experiments of ranging accuracy and ranging stability are completed. The results show that the system can realize reliable bidirectional communication between the LIN master node circuit and the ultrasonic transceiver unit, which realizes the transformerless driving. The system can realize the distance measurement within the range of 250–2700 mm, and the measurement error is less than 30 mm. The measurement fluctuation is less than 10 mm, which provides a new solution for the ultrasonic ranging system in the potentially explosive atmosphere.