11.
Johnsson, Dennis, et al.
(författare)
Two-level Reconfigurable Architecture for High-Performance Signal Processing
2004
Ingår i: ERSA'04, The 2004 International Conference on Engineering of Reconfigurable Systems and Algorithms. - Arthens : CSREA Press. - 9781932415421 ; , s. 177-183
Konferensbidrag (refereegranskat) abstract
High speed signal processing is often performed as a pipeline of functions on streams or blocks of data. In order to obtain both flexibility and performance, parallel, reconfigurable array structures are suitable for such processing. The array topology can be used both on the micro and macro-levels, i.e. both when mapping a function on a fine-grained array structure and when mapping a set of functions on different nodes in a coarse-grained array. We outline an architecture on the macro-level as well as explore the use of an existing, commercial, word level reconfigurable architecture on the micro-level. We implement an FFT algorithm in order to determine how much of the available resources are needed for controlling the computations. Having no program memory and instruction sequencing available, a large fraction, 70%, of the used resources is used for controlling the computations, but this is still more efficient than having statically dedicated resources for control. Data can stream through the array at maximum I/O rate, while computing FFTs. The paper also shows how pipelining of the FFT algorithm over a two-level reconfigurable array of arrays can be done in various ways, depending on the application demands.
12.
Axmon, Joakim
(författare)
Two-Dimensional Signal Root Estimation in Blind Multichannel Impact Response Analysis
2004
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
This doctoral dissertation concerns two-dimensional frequency estimation for modal analysis of single-input multiple-output impact responses from circularly cylindrical objects. The application is within detection of internal defects in trunks of spruce. The material consists of impact responses from 94 trees, with 66 sound and 28 in various stages of decay. Paper I proposes that modal analysis of trunks of spruce may unveil the presence of internal defects, which are hypothesised to result in a reduction of the modal frequencies. The responses, collected using a uniform linear array of accelerometers encircling a cross-section, contain two-dimensional spatiotemporal modes which are sinusoidal and temporally damped. The spatial mode-shapes are used for ensuring that comparisons of modal frequencies on a tree-to-tree basis are performed on corresponding modes. The frequency analysis is based on cascading of a polynomial-based estimator for the temporal dimension and DFTs for the spatial dimension. The results show that the modal frequencies often are lower for trees in decay than for sound trees, but also, that the groups partially overlap, and that the results for sound trees with matching dimensions are scattered. Paper II is based on the results in Paper I, and addresses a method for reduction of scatter within the group of sound trees, using one additional parameter that can be estimated from the impact responses. Furthermore, a detector is proposed, and its performance is found to be better than performance reported elsewhere for visual tree examination. Paper III presents a novel technique, called partial forward-backward averaging, that enhances two-dimensional state-space/subspace rotation-based frequency estimation for the kind of modes encountered in the current application. Conventional estimators do not account for all symmetries inherent in this particular kind of modes, and consequently, the quality of the resulting estimates is poor. The novel technique, model-based enhancement of signal subspace estimation, results in estimates with better properties and lower bias and variance. Paper IV contains a full re-analysis of, and a comparison with, the material reported on in Paper I. A fast implementation of a state-space/subspace rotation-based algorithm, detailed in Paper III, is derived and used for the analysis. It has been hypothesised that the modal frequencies change when a tree is subjected to impact excitation repeatedly, since the impacts are applied onto a screw which inevitably is forced deeper and deeper into the trunk. No such effect is found, so this hypothesis is rejected.
13.
Bengtsson, Lars, 1963
(författare)
Elektriska mätsystem och mätmetoder
2003
Bok (övrigt vetenskapligt/konstnärligt) abstract
Elektrisk mätteknik spänner över ett brett teknikområde och har utvecklats till något av ett tvärtekniskt ingenjörsämne. Den här boken tar fasta på detta och behandlar en lång rad aspekter på elektriska mätsystem och mätmetoder. Boken innehåller t ex en detaljerad genomgång av givare, förstärkare och AD-omvandlare. Mätinstrument med inbyggda signalbehandlingsfunktioner som t ex frekvensanalys, korrelation och medelvärdesbildning utgör en stor del av innehållet. Även filter, både analoga och digitala behandlas. Mätinstrumentens och anslutningskablarnas inverkan på mätvärdet behandlas detaljerat liksom elektromagnetisk störningskoppling och EMC-aspekter på mätsystem, smat databehandling i form av mätosäkerhetsanalyser och kurvanpassning. I boken finns också en presentation av det grafiska programspråket LabVIEW.
14.
Berrebi, Jonathan, et al.
(författare)
Ultrasonic flow metering errors due to pulsating flow
2004
Ingår i: Flow Measurement and Instrumentation. - : Elsevier BV. - 0955-5986 .- 1873-6998. ; 15:3, s. 179-185
Tidskriftsartikel (refereegranskat) abstract
Transit-time ultrasonic flow meters present some advantages over other flow meters for district heating industries. They are both accurate and non-intrusive. It is well-known that ultrasonic flow meters are sensitive to installation effects. Installation effects could be static or dynamic. Among the possible dynamic installation effects is pulsating flow. The influence of pulsating flow on the prediction and the zero-crossing operations is investigated. Expressions are found for the prediction error and the zero-crossing error. The relative errors due to the prediction and the zero-crossing are plotted. The prediction error can reach dramatic values while the zero-crossing operation is hardly influenced by flow pulsations.
15.
Carlander, Carl, et al.
(författare)
Temperature and installation effects on small commercial ultrasonic flow meters
2000
Konferensbidrag (refereegranskat) abstract
Experimental work has been performed on a selection of small ultrasonic flow meters for water. This work was accomplished in order to investigate the in fluence of temperature and flow profile disturbances on the performance of flow meters in district heating applications. The flow meters tested were all ultrasonic flow meters of sing-around type. The selection of flow meters contains in total seven meters of three different brands. All meters have a flow range from 0.015 m3/h to 1.5 m3/h. These meters are commonly used in heat meters in small district heating subscriber stations. The flow meters are presented without identification. All tests were performed in a flow meter calibration facility and in a flow range including the minimum and maximum flow of each flow meter. In the tests three different water tempera-tures and three different installations were investigated. Water temperatures of 20 °C, 50 °C and 70 °C were used. These temperatures are representative for district heating applications. The installations tested involved flow meters mounted with long straight pipes both up-and down-stream representing ideal conditions, a single elbow and a double elbow out of plane both generating disturbed flow profiles. All set-ups are in accordance with the flow meter specifications. The results demonstrate that both the change in temperature and the disturbed flow profiles introduce errors in the flow measurements. The change from 20 °C to 50 °C and 70 °C can cause a shift in meter performance larger than the specified maximum permissible error. Compared with the ideal installation the installations generating disturbed flow profiles cause errors up to more than 2 %. The errors due to temperature and installation effects have a bias to add when combined. This might lead to even larger errors.
16.
Carlson, Johan, et al.
(författare)
Accurate temperature estimation in ultrasonic pulse-echo systems
2003
Ingår i: 5th world congress on ultrasonics WCU 2003. - Paris : Institut Biomedical des Cordeliers, Université Pierre et Marie Curie. - 2952110506 ; , s. 1565-1568
Konferensbidrag (refereegranskat) abstract
Ultrasonic pulse-echo systems are widely used to estimate properties of liquids and gases. A common principle is to use a buffer material (buffer-rod) fixed to the ultrasound transducer. Assuming the acoustic properties of the buffer-rod are known, it is then possible to calculate the acoustic impedance of the unknown material. A problem occurs if the temperature of the buffer-rod changes during the measurements, since the properties of the buffer-rod, such as the acoustic attenuation depends on temperature. If, however, the temperature is recognized, it is possible to compensate for this. In this paper we present a method based on speed of sound changes in the buffer-rod to estimate the temperature. With the resulting model we are able to estimate temperatures in PMMA for the interval 5°C to 60°C with a 0.1 °C accuracy (at a 95% confidence level).
17.
Carlson, Johan, et al.
(författare)
Frequency and temperature dependence of acoustic properties of polymers used in pulse-echo systems
2003
Ingår i: Proceedings, 2003 IEEE Ultrasonics Symposium. - Piscataway, NJ : IEEE Communications Society. - 0780379225 ; , s. 885-888
Konferensbidrag (refereegranskat) abstract
In ultrasonic pulse-echo systems, polymers like PMMA (polymethylmethacrylate) and PEEK (polyetheretherketone) are often used as buffer-rods, placed between the ultrasound transducer and the unknown material (liquid, gas, or solid material). Provided the acoustic properties of the buffer-rods are known, it is possible to calculate these also for the unknown material, based on reflections between the buffer-rod and the unknown medium. However, temperature changes also affect these properties. In this paper we present a method for measuring acoustic attenuation, speed of sound and density, for buffer-rod materials. We also give experimental values for PMMA and PEEK, for temperatures between 5/spl deg/C and 37/spl deg/C, and for 5 MHz and 10 MHz ultrasound frequency.
18.
Martinsson, Pär-Erik, et al.
(författare)
Incorporation of diffraction effects in simulations of ultrasonic systems using PSpice models
2001
Ingår i: Proceedings. - Piscataway, NJ : IEEE Communications Society. - 0780371771 ; , s. 405-410
Konferensbidrag (refereegranskat) abstract
The use of PSpice models for piezoelectric devices and ultrasonic transmission media is of major importance in the design of electronics for ultrasonic systems. Today, these models include viscoelastic loss but disregard loss due to diffraction, i.e. beam spreading. This paper presents a method to include diffraction loss in PSpice simulations of ultrasonic systems. The conductive loss in the transmission line, that models the propagation media of the ultrasound pulse, is used to model the loss due to diffraction. Parameter variations for the piezoelectric device can affect the result greatly. Thus, a sensitivity analysis for the simulation model is presented. Measurements and simulations have been performed using a pulse echo system in water. Maximum distance to the reflector was 200 mm. The piezoelectric devices used were PZ-27 crystals with diameters 6 mm and 12 mm, with a center frequency of 4 MHz. Results show that the simulated amplitude of the echo follows measured values well in both near and far fields, with an offset of about 10%.
19.
Martinsson, Pär-Erik, et al.
(författare)
Ultrasonic measurements of molecular relaxation in ethane and carbon monoxide
2002
Ingår i: Proceedings. - Piscataway, NJ : IEEE Communications Society. - 0780375823 ; , s. 511-516
Konferensbidrag (refereegranskat) abstract
This paper describes how molecular relaxation can be measured using ultrasound. The velocity and absorption of sound varies with frequency due to molecular relaxation. By measuring these variation the relaxation strength and the effective relaxation time for singular relaxations can be calculated. This paper describes initial measurements performed in order to survey the sound properties in gases both experimentally and theoretically.
20.
