Ultrasonic Sensor System Research Articles

Ultrasonic sensor system for CaF2 interface monitoring with rods permanently embedded in crystal

The interface position of a CaF2 crystal was successfully monitored during growth using an innovative ultrasonic sensor system. The sensor system utilizes a top entry approach consisting of probe rods permanently positioned at the bottom of the crucible. Ultrasonic time of flight data (TOF) is used to determine interface position. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Electrorheological tactel elements

The use of ultrasound systems for medical examination and diagnosis is nothing new. The extension of ultrasound techniques for real time elastographic analysis purposes represents a more recent development. Nevertheless, as they stand all such techniques rely on the interpretation of two-dimensional visual data displayed on a video screen. In reality however, a medical doctor will make as much use of exploratory touch as he or she does vision, making the simultaneous portrayal of both video and tactile information most desirable [Böse H, Monkman GJ, Freimuth H, Ermert H. Haptisches Sensor-Aktor-System uaf der grundlage der Echtzeitelastographie sowie von elktro- und magnetorheologischen Materialien “HASASEM” [3]. BMBF Antrag 01 IR A14D, Oktober 2000]. This paper discusses the preliminary tests and basic design parameters for single tactels using electrorheological fluids. The final aim is to produce a prototype three-dimensional tactile display comprising electrically switchable micro-machined cells whose mechanical moduli are governed by phase changes experienced by electrorheological fluids. This will be integrated with the latest elastographic ultrasonic sensor systems in order to present the human fingers with controllable surfaces capable of emulating biological tissue, muscle and bone.

VARIABLE RATE NITROGEN APPLICATION IN FLORIDA CITRUS BASED ON ULTRASONICALLY-SENSED TREE SIZE

Most Florida citrus groves are still managed as large contiguous uniform blocks, despite significant variation infruit yield and tree canopy size. Site-specific grove management by variable rate delivery of inputs such as fertilizers on atree size basis could improve horticultural profitability and environmental protection. Tree canopy sizes were measuredreal-time in a typical 17-ha Valencia grove with an automated ultrasonic sensor system equipped with Differential GlobalPositioning System (DGPS). Prescription maps for variable application of nitrogen fertilizer were generated fromultrasonically scanned tree sizes on a single tree basis using ArcView GIS and Midtech Fieldware. Leaf samples from treeswith different canopy sizes, which had been fertilized at a conventional uniform rate of 270 kg N/ha/y, were analyzed fornitrogen concentration. Analysis of 2980 tree spaces in the grove showed a skewed size distribution, with 62% in the 0- to100-m3/tree volume classes and a median volume of 79 m3/tree. The tree volumes ranged from 0 to 240 m3/tree. Regressionanalysis showed that trees with excess leaf nitrogen (>3%) had canopies less than 100 m3. These trees receiving excessnitrogen are likely to have lower fruit yields and quality, and wasted fertilizer nitrates may leach beyond the root zone togroundwater. In order to rectify the excess fertilization of smaller trees, a granular fertilizer spreader with hydraulicallypowered split-chain outputs controlled with a MidTech Legacy 6000 controller was used for variable rate application ofnitrogen in one-half of the grove. A 38% to 40% saving in granular fertilizer cost was achieved for this grove when variableN rates were implemented on a per-tree basis ranging from 135 to 270 kg N/ha/y.

環境認識のための超音波センサシステムの設計と実装(非接触センシング)

We are interested in the ultrasonic sensors which can be used with vision sensors for environment recognition. Ultrasonic sensors are economic, can measure long distance precisely, and compute the distance from obstacle faster than vision sensors. This paper describes the ultrasonic sensor system which can measured distance and recognize object’s shape and material. Using this system, mobile robots can find and classify obstacles by shape and material punctually without vast amounts of computation as vision sensors. Further fact that applying ultrasonic sensor with vision sensors brings mobile robots more information.

A new ultrasonic temperature measurement system for air conditioners in automobiles

This paper presents a microcomputer-based ultrasonic temperature sensor system tomeasure the temperature of an air conditioner (AC) in an automobile. It usesthe ultrasonic measurement of the changes in the speed of sound in the air todetermine the temperature of the environmental air. The changes in the speedof sound are calculated by combining time-of-flight (TOF) and phase shifttechniques. This method can work in a wider range than using phase shift aloneand is more accurate than the TOF scheme. In the proposed system, we use40 ± 2 kHz ultrasonic transducers and adopt a single-pass operation. An 89c51 single-chipmicrocomputer-based binary frequency shift-keyed (BFSK) signal generator andphase detector are designed to record and calculate the TOF, phase shiftof the two frequencies and temperature. These data are then sent to eitheran LCD display or to a PC for calibration and examination. Experimentalresults show that the proposed measurement system has a high accuracy of ± 0.4 °C from0 to 80 °C and can reflect the temperature change within 100 ms.

Feature extraction method for a robot map using neural networks

Many map-building algorithms using ultrasonic sensors have been developed for mobile robot applications. In indoor environments, the ultrasonic sensor system gives some uncertain data. To compensate for this effect, a new feature extraction method using neural networks is proposed. A new, effective representation of the target is defined, and the reflection wave data patterns are learnt using neural networks. As a consequence, the targets are classified as planes, corners, or edges, which all frequently occur in indoor environments. We constructed our own robot system for the experiments which were carried out to show the performance.

전역 초음파 센서 시스템을 이용한 이동 로봇의 자기 위치 추정

A global ultrasonic sensor system for self-localization of a mobile robot is proposed in this paper. The global ultrasonic sensor system consists of three or more ultrasonic transmitters fixed at some positions in the world coordinate and receivers in the moving coordinate of a mobile robot. In this global sensor system it is easy to get state vector of the mobile robot in the world coordinate from the distance information between each ultrasonic transmitter and receiver. An extended kalman filter algorithm is used to process the noisy ultrasonic signal and to estimate the state vector. In case of using several independent ultrasonic transmitters, it is necessary to avoid the cross talk among the ultrasonic waves and to synchronize between each ultrasonic transmitter and receiver. The small sized radio frequency modules are adopted to solve the cross talk and the synchronization problem Computer simulation and experiments are carried out to verify the effectiveness of the proposed ultrasonic sensor system.

Ultrasonic sensor system to detect solids in a milk pasteurization process

In the food industry, many products require a specific process. In the milk industry, the raw milk passes through several process stages before reaching the end user in a very qualitative and healthy way. One of the problems of the milk is that it can contain solids in suspension, result of contamination of the milk, or inherent to the pasteurization process itself. In order to control these solids, a solid detection system is being developed, which will detect the solids by the reflection and refraction of ultrasonic waves. The sensor must be set in the upper part of the milk containers, and with a grid array to allow the control system to prevent these solids from entering into the pipes of the processing plant. The sensing system may activate an acoustic alarm to indicate that a solid has been detected, and a visual one to indicate the affected part of the process. (To be presented in Spanish.)

Multifrequency CW-based time-delay estimation for proximity ultrasonic sensors

With conventional pulse-echo ranging approaches it is difficult to obtain an accurate range measurement needed by a proximity ultrasonic sensor system owing to the limited bandwidth of the transducer. A continuous-wave multifrequency ranging method is presented to accurately measure the proximity distance for an ultrasonic distance sensor system. A novel time-delay estimator is derived based on a nonlinear least-squares-fitting criterion for the case where the received signal amplitude is non-negative owing to the acoustically hard reflection. To minimise the highly oscillatory cost function an efficient two-stage estimation algorithm is proposed. Numerical results show that the estimation algorithm can approach the Cramér–Rao bound as the signal-to-noise ratio increases.

829 三次元空間を認識するための超音波センサに関する研究

The main purpose of this research is to develop ultrasonic sensor system for flying robot in indoor environment. In this way, some researchers have made ultrasonic sensor system for 2-dimensional space. But flying robot needs ultrasonic system for 3-dimensional space. There is a method using the ultrasonic sensor which has an array type transmitter as a method of measuring 3-dimensional environment. However, if a sensor is used as an array type, weight will increase so much and the merit using an ultrasonic sensor will decrease. So we represented some ultrasonic sensor system for 3-dimensional space. After making and comparing these systems we decided one system that has 4 receive sensors disposed cross and centered transmitter on the robot, and calculated circuit and pc on the ground. We acquired the orbit of proceeding flying robot to test his system to investigate performance of sensor range.

CW-based proximity distance measurement by ultrasonic sensors

With conventional pulse-echo ranging approaches, it is difficult to obtain an accurate range measurement needed by a proximity ultrasonic sensor system due to the limited bandwidth of the transducer. However, based on the continuous wave (CW) method (i.e., the transducer is excited by a set of continuous harmonic signals), the high accuracy can be obtained even with a narrow-band transducer. By using a set of orthogonal sinusoid signals and simultaneously measuring the phase shifts corresponding to all of the frequencies, we obtain a fast measurement scheme with respect to the traditional CW method that measures the phase shifts for each frequency separately. This method can be efficiently implemented by FFT by currently available dedicated DSP chips. To estimate the unknown distance based on the phase shifts, two-stage fast optimization algorithm has been presented. Numerical results show that this algorithm can approach the Cramer–Rao bound (CRB) for high signal-to-noise ratio.

In-line concentration measurement in complex liquids using ultrasonic sensors

Recently there has been increased demand for chemical sensors measuring in-line the concentration of selected substances in complex liquids in order to guarantee a high product quality in the process industry. At present there is a great interest in acoustic sensor systems for concentration measurements. This article presents a new ultrasonic sensor system consisting of a miniaturized multi-sensor arrangement for the comprehensive acoustic characterization of liquid mixtures. The sensor system measures sound velocity, impedance coefficient, attenuation coefficient and temperature.

A new prototype intelligent mobility system to assist powered wheelchair users

This paper presents new prototype powered wheelchair systems that are easy to use and safe. The systems use simple ultrasonic sensor systems to assist users in steering their powered wheelchairs. The new systems could improve the chances of some disabled children learning that behaviour and interaction with the environment can be controlled. An overview of the benefits to be offered by an automated wheelchair is included. Some results, problems and difficulties are described along with an assessment of the current position and the way forward.

Ultrasonic potential field sensor for obstacle avoidance

We introduce an ultrasonic sensor system that measures artificial potential fields (APFs) directly. The APF is derived from the traveling-times of the transmitted pulses. Advantages of the sensor are that it needs only three transducers, that its design is simple, and that it measures a quantity that can be used directly for simple navigation, such as collision avoidance.

Ultrasonic sensors for process monitoring and chemical analysis: state-of-the-art and trends

Ultrasonic sensors are used in a large variety of ways. New fields of ultrasonic: sensor and ultrasonic sensor system applications are process monitoring and control, automotive techniques and chemical analysis. These applications have enjoyed a rapid increase of interest in recent years. The development of new ultrasonic sensors or systems was and is essentially accelerated by the progress in electronics, by new piezoelectric materials, by exploitation of new technologies and by the need for new or more accurate analysis methods in many industrial branches. A review of ultrasonic sensors based on piezoelectric materials and resonators is presented. First, the physical background for ultrasonic wave propagation and corresponding technical applications is given. A definition of the ultrasonic sensor system is introduced later because an ultrasonic sensor alone makes no sense. For an efficient use of this sensor principle, a well-developed transmitter and receiver electronics and intelligent data-acquisition electronics are necessary. Secondly, it is shown that ultrasonic sensors can be divided into four groups depending on how the ultrasonic signal has been changed on its path during propagation or the transducer properties are changed by interaction with the surroundings. The present state of established sensors for flow, distance and level is discussed. Ultrasonic sensors for process monitoring are described. New application fields for these sensors can be predicted. Finally, ultrasonic microsensors are introduced. A description of their state-of-the-art and application examples are given. To conclude, the use of new technologies for the manufacture of miniaturized ultrasonic sensors and future developments are discussed.

Miniaturized ultrasonic sensor system for liquid analysis

At the moment, known commercial devices to measure the sound velocity in liquids are limited in their application because the relation between velocity and concentration of substances is often not clear, for instance, if it is a parabolic curve. Additionally, the temperature dependence shows similar behavior. This contribution will present an ultrasonic sensor system consisting of a miniaturized multisensor arrangement for the comprehensive acoustic characterization of liquid mixtures. The sensor is based on segmented cylindrical piezoceramics and measures velocity, impedance coefficient, attenuation coefficient, and temperature. If it is a known liquid mixture it is possible to use the measuring quantities to calculate the material properties acoustical impedance and absorption or the concentration of selected substances in complex liquids. The sensor system is able to adapt itself to different and changeable absorption conditions which is typical of industrial processes. The measuring chamber is optimized to investigate small volumes of liquid specimens. In this contribution the sensor design and the developed approach for the continuous and simultaneous measurement of acoustic properties of liquids will be described. Application examples of the sensor in the chemical and food industry will show the advantages and limits of our new sensor system.

Grid Map Building from Reduced Sonar Data

In this paper an ultrasonic sensor is presented, aimed to map building in autonomous robot applications. By means of a rotary movement the sensor can be settled up to 200 angular positions. The data processing performed in the sensor module gives more elaborated data than the usual ToF ultrasonic sensor systems and it is possible to detect all objects placed in the scenario with its signal amplitude value. Due to the quality of data is possible to reduce the amount of angular readings required to construct the map. As results indicate it is possible to obtain good maps using only a very reduced set of readings.

Sonar sensing for low-cost indoor mobility

Abstract Low-cost autonomous mobility poses an important challenge on the way to new robot applications. Ultrasonic sensor systems are both robust and low-cost. We therefore have investigated the usefulness of several types of ultrasonic sensor principles for obstacle avoidance and localisation. Our experiments show that by tailoring the algorithms to the specific sensing task at hand, autonomous mobility can to a wide extent be achieved with a simple monaural system. However, some drawbacks like limited speed and resolution in map building remain. These drawbacks can be overcome by more advanced ultrasonic sensor systems, where two or three receivers instead of one are used in order to get more data from one single measurement.

Machine of the future: An intelligent paper roll manipulator

A general description of a control system for a prototype of an intelligent and skilled paper roll manipulator (PRM) is given. The elementary operations related to both manipulations and environment observations are described, and explanation regarding the integration of these with a hierarchically organized planning-executing-monitoring architecture (PEM) is given. The kernel of PEM architecture is a goal-oriented module consisting of these three principle parts. The motion control of the paper roll manipulator is divided into free motion (gross motion) and force-constrained motion (fine motion) phases. Gross motion control takes the paper roll from the starting position to the vicinity of the goal position, whereas the fine motion control is used in placing the paper roll against other paper rolls and the support, e.g. the other paper rolls and walls of a ship. For coarse recognition of the environment a 3D laser device is used. The accurate position of paper rolls in the picking phases is measured with the aid of an ultrasonic sensor system, and the final force constrained placement is carried out with force-sensing based on measurements of hydraulic pressures of the manipulator system.

Investigation of Lamb waves for sensor applications in semiconductor processing

Considering the semiconductor wafers as anisotropic plates, Lamb wave propagation characteristics are related to various parameters dynamically changing during processing. Particularly, the effect of wafer temperature and thin-film growth on phase velocity of zeroth order Lamb waves are analyzed theoretically. These modes are chosen to enable single mode operation in silicon wafers for frequency-thickness product (f*d) less than 3 MHz mm. The surface impedance approach is used in theoretical modeling of propagation in general multilayered anisotropic solid structures. Temperature, thin film, and their combined sensitivity figures are calculated for commonly used structures in semiconductor processing. The results are interpreted to obtain optimum ultrasonic sensor system parameters for certain applications. For example, in case of aluminum films on (100) silicon, antisymmetric mode in 〈100〉 direction shows negligible sensitivity to thin films around f*d=0.8 MHz mm. The same figure for silicon oxide film is 1.57 MHz mm. In a combined measurement, a temperature sensor using these system parameters to measure phase velocity will be minimally affected by thin films, enabling an isolated temperature measurement. Practical implementations of the results in rapid thermal processing environment are also discussed in the paper. [Work supported by SRC.]