Modal analysis and nonlinear characterization of an airborne power ultrasonic transducer with rectangular plate radiator

Some industrial processes like particle agglomeration or food dehydration among others can be enhanced by the use of power ultrasonic technologies. These technologies are based on an airborne power ultrasonic transducer (APUT) constituted by a pre-stressed Langevin-type transducer, a mechanical amplifier and an extensive plate radiator. In order to produce the desired effects in industrial processing, the transducer has to vibrate in an extensional mode driving an extensive radiator in the desired flexural mode with high amplitude displacements. Due to the generation of these high amplitude displacements in the radiator surfaces, non-linear effects like frequency shifts, hysteresis or modal interactions, among others, may be produced in the transducer behavior. When any nonlinear effect appears, when applying power, the stability and efficiency of this ultrasonic technology decreases, and the transducer may be damaged depending on the excitation power level and the nature of the nonlinearity. In this paper, an APUT with flat rectangular radiator is presented, as the active part of an innovative system with stepped reflectors. The nonlinear behavior of the APUT has been characterized numerically and experimentally in case of the modal analysis and experimentally in the case of dynamic analysis. According to the results obtained after the experiments, no modal interactions are expected, nor do other nonlinear effects

A Study on the Compensation Algorithm for Inertial Navigation System

This paper describes a method that how a relatively compensate the position errors in the using of low cost Inertial Measurement Unit (IMU) has been evaluated and compared with the well established method based on a Kalman Filter (KF). The compensation algorithm for IMU has been applied to the problem of integrating information in Inertial Navigation System (INS). The KF is used to estimate and compensate the errors of an INS by using the integrated INS velocity and position, respectively. First by using Kalman Filter, we try to reduce noise of acceleration data, where two of an acceleration, constant drift and period drift, are considered. With the constant drift, it depends on sensor and it always keeps on constant error. When using double integration for calculates distance and velocity, these kinds of drifts can make increasing velocity and position errors. So, we tried to find these errors and used constant compensation algorithm for compensation of errors in data. Second, external environment circumstance is changed ordinarily. Almost of them can be changed on periodic time. The average drift can be obtained during constant periodic time. And use this value, we consider with a factor as a periodic external disturbance which affects to the exact position. We used a repetitive method to reduce the external environment change. We verified the proposed algorithm by simulation results.Abstract Chapter 1. Introduction 3 1.1 Background and objective 3 1.2 Inertial navigation system 4 Chapter 2. The Kalman filter and application in INS 7 2.1 The Kalman filter 7 2.2 Acceleration sensors 12 2.3 Acceleration problems 17 2.4 Application in INS 18 Chapter 3. Design method for Drift compensation gain 19 3.1 Design method for constant drift compensation gain 19 3.2 Design method for Periodic drift compensation gain 21 Chapter 4. Implementation and results 24 4.1 Using Kalman filter and IMU bias 24 4.2 Constant bias compensation 28 4.3 Periodic bias compensation 30 Chapter 5. Conclusions 35 References 3

MEMS Gyroscopes for Consumers and Industrial Applications

none2mixedAntonello, Riccardo; Oboe, RobertoAntonello, Riccardo; Oboe, Robert

Vaihtoehtoiset mittausmenetelmät merirakenteiden iskukuormille

In this thesis the prospects of different sensor technologies for impact measurements have been researched and tested. Main goal was to implement impact measurement system for an already known structure. Metallic foil strain gauges and fiber Bragg grating sensors have been previously used, but for cost reasons cheaper alternative with similar accuracy is searched for. Researched sensors include vibrating wire strain gauges, LVDTs, accelerometers, SAW sensors, semiconductor strain gauges, photoelectric sensors and ultrasonic sensors. It was concluded that accelerometers exhibit many good qualities especially for impact measurements in difficult conditions. A consistent method for position estimation was to detect the impact peaks from the data and only to integrate over the measured peaks to shorten the integral timespan. Minimizing the integral timespan, also minimizes the drift. To detect maximums of the impacts, clustering in conjunction with peak detection was used. To assess the accuracy of accelerometers' position estimates, some testing with a measurement system was also made. Tests were made with capacitive, thermal and piezoelectric accelerometers with varying test parameters to see how well each type of sensor performs in different scenarios. Both the impulse duration and sensor movement range were altered according to the known system's typical ranges. It was determined that accelerometers are a valid option for estimation of strain caused by impacts. The most accurate estimation was achieved with thermal and capacitive accelerometers. Though, piezoelectric and piezoresistive sensors should be preferred in the case of higher accelerations.Tässä työssä tutkittiin ja testattiin erilaisten anturien soveltuvuutta iskukuormien mittaamiseen. Työn tavoitteena on implementoida iskukuormien mittaus jo tunnetulle rakenteelle. Entuudestaan oli käytetty metallisia ja optisia venymäliuskoja, mutta kustannus-syistä johtuen etsittiin halvempaa vaihtoehtoa, jonka tarkkuus on samaa suuruusluokkaa. Työssä vertailtiin ja tutkittiin metallilankavenymäliuskoja, LVDT-antureita, kiihtyvyysantureita, SAW-antureita, puolijohdevenymäliuskoja, välosähköisiä antureita ja ultraääniantureita. Tultiin tulokseen, että kiihtyvyysanturit soveltuvat hyvin iskukuormien mittaamiseen. Iskukuorman aiheuttaman etäisyyden muutoksen estimoimiseen käytettiin menetelmää, jossa aluksi iskujen aiheuttamat huiput tunnistettiin datasta, jonka jälkeen vain ensimmäisen aallon yli integroitiin kahdesti paikkaestimaatin muodostamiseksi. Klusterointia käytettiin iskujen erottamiseksi toisistaan. Klusteroinnilla ja huipunhaulla saatiin integrointiväli minimoitua, jotta estimaattien arvot eivät ajelehtisi. Anturien ja estimointimenetelmän tarkkuuden selvittämiseksi rakennettiin testijärjestelmä. Antureita poikkeutettiin erilaisilla impulssien kestoilla ja voimakkuuksilla. Testejä tehtiin kapasitiivisilla, piezosähköisillä ja termokiihtyvyysantureilla. Kokeilla todistettiin, että kiihtyvyysanturit ovat validi vaihtoehto iskukuormien mittaamiseen. Tarkimmat estimaatit saatiin kapasitiivisella ja termokiihtyvyysanturilla. Tosin, piezosähköisten ja piezoresistiivisten kiihtyvyysantureiden käyttöä kannattaa harkita, kun kyseessä on suuret kiihtyvyydet

Coriolis flowmeters: A review of developments over the past 20 years, and an assessment of the state of the art and likely future directions

This paper starts from a brief revisit of key early published work so that an overview of modern Coriolis flowmeters can be provided based on a historical background. The paper, then, focuses on providing an updated review of Coriolis flow measurement technology over the past 20 years. Published research work and industrial Coriolis flowmeter design are both reviewed in details. It is the intention of this paper to provide a comprehensive review study of all important topics in the subject, which include interesting theoretical and experimental studies and innovative industrial developments and applications. The advances in fundamental understanding and technology development are clearly identified. Future directions in various areas together with some open questions are also outlined.This is the accepted manuscript version. The final version is available from Elsevier at http://dx.doi.org/10.1016/j.flowmeasinst.2014.08.01

A Thermally actuated microelectromechanical (MEMS) device for measuring viscosity

A thermally actuated non-cantilever-beam micro-electro-mechanical viscosity sensor is presented. The proposed device is based on thermally induced vibrations of a silicon-based membrane and its damping due to the surrounding fluid. This vibration viscometer device utilizes thermal actuation through an in-situ resistive heater and piezoresistive sensing, both of which utilize CMOS compatible materials leading to an inexpensive and reliable system. Due to the nature of the actuation, thermal analysis was performed utilizing PN diodes embedded in the silicon membrane to monitor its temperature. This analysis determined the minimum heater voltage pulse amplitude and time in order to prevent heat loss to the oil under test that would lead to local viscosity changes. In order to study the natural vibration behavior of the complex multilayer membrane that is needed for the proposed sensor, a designed experiment was carried out. In this experiment, the effects of the material composition of the membrane and the size of the actuation heater were studied in detail with respect to their effects on the natural frequency of vibration. To confirm the validity of these measurements, Finite Element Analysis and white-light interferometry were utilized. Further characterization of the natural frequency of vibration of the membranes was carried out at elevated temperatures to explore the effects of temperature. Complex interactions take place among the different layers that compose the membrane structures. Finally, viscosity measurements were performed and compared to standard calibrated oils as well as to motor oils measured on a commercial cone-and-plate viscometer. The experimentally obtained data is compared to theoretical predictions and an empirically-derived model to predict viscosity from vibration measurements is proposed. Frequency correlation to viscosity was shown to be the best indicator for the range of viscosities tested with lower error (+/- 5%), than that of quality factor (+/- 20%). Further viscosity measurements were taken at elevated temperatures and over long periods of time to explore the device reliability and drift. Finally, further size reduction of the device was explored

An optical distance sensor : tilt robust differential confocal measurement with mm range and nm uncertainty

Compared with conventional high-end optical systems, application of freeform optics offers many advantages. Their widespread use, however, is held back by the lack of a suitable measurement method.The NANOMEFOS project aims at realizing a universal freeform measurement machine to fill that void.The principle of operation of this machine requires a novel sensor for surface distance measurement, the development and realization of which is the objective of the work presented in this thesis. The sensor must enable non-contact, absolute distance measurement of surfaces with reflectivities from 3.5% to 99% over 5 mm range, with 1 nm resolution and a 2s measurement uncertainty of 10 nm for surfaces perpendicular to the measurement direction and 35 nm for surfaces with tilts up to 5°. To meet these requirements, a dual-stage design is proposed: a primary measurement system tracks the surface under test by translating its object lens, while the secondary measurement system measures the displacement of this object lens. After an assessment of various measurement principles through comparison of characteristics inherent to their principle of operation and the possibilities for adaptation, the differential confocal measurement has been selected as the primary measurement method. Interferometry is used as secondary measurement method. To allow for correction of tilt dependent error through calibration, a third measurement system has been added, which measures through which part of the aperture the light returns. An analytical model of the differential confocal measurement principle has been derived to enable optimization. To gain experience with differential confocal measurement, a demonstrator has been built, which has resulted in insights and design rules for prototype development. The models show satisfactory agreement with the experimental results generated using the demonstrator, thus building confidence that the models can be applied as design and optimization tools. Various properties that characterize the performance of a differential confocal measurement system have been identified. Their dependence on the design parameters has been studied through simulations based on the models. The results of this study are applied to optimize the sensor for use in NANOMEFOS. An optical system has been designed in which the interferometer and the differential confocal systems are integrated in a compact design. The optical path of the differential confocal system has been folded using prisms and mirrors so that it can be realized within the allotted volume envelope. For the same reason, many components are adapted from commercially available parts or are custom made. An optomechanical and mechatronic design has been made around the optical system. A custom focusing unit has been designed that comprises a guidance mechanism and actuator to enable tracking of the surface. To achieve a low measurement uncertainty, it aims at accurate motion, high bandwidth and low dissipation. The lateral position of the guidance reproduces within 20 nm and from the frequency response, it is expected that a control bandwidth of at least 800 Hz can be realized. Power dissipation depends on the form of the freeform surface and is a few mW for most expected trajectories. Partly custom electronics are used for signal processing, and to drive the laser and the focusing unit. Control strategies for interferometer nulling, focus locking and surface tracking have been developed, implemented and tested. Various tests have been performed on the system to evaluate the performance. Calibrations must be carried out to achieve the required measurement uncertainty. One calibration is based on a new method to measure tilt dependency of distance sensors. The sensor realized has 5 mm measurement range, -2.5 µm to 1.5 µm tracking range, sub-nanometer resolution, and a small-signal bandwidth of 150 kHz. Using the test results, the 2s measurement uncertainty after calibration is estimated to be 4.2 nm for measurement of rotationally symmetric surfaces, 21 nm for measurement of medium freeform surfaces and 34 nm for measurement of heavily freeform surfaces. To test the performance of the machine with the sensor integrated, measurements of a tilted flat have been carried out. In these measurements, a tilted flat serves as a reference freeform with known surface form. The measurements demonstrate the reduction of tilt dependent error using the new calibration method. A tilt robust, single point distance sensor with millimeter range and nanometer uncertainty has been developed, realized and tested. It is installed in the freeform measurement machine for which it has been developed and is currently used for the measurement of optical surfaces