Genetic algorithm application for electrodynamic transducer model identification

Research object: the adaptation and application of the genetic algorithm for electrodynamic transducer model parameters identification. Investigated problem: to formulate loudspeaker identification task as an optimization problem, adapt it to the genetic algorithm framework and compare obtained results with classical identification method using added mass. Main scientific results: the complete genetic algorithm loudspeaker identification procedure is presented, including: – data acquisition scheme, where the directly measured values for the algorithm application are: voltage at loudspeaker terminals, current through the voice coil and displacement of the moving part – selection of an appropriate set of genes of an individual – derivation of the fitness function for assessing the quality of the identified parameters, which can also be used to identify other types of electroacoustic transducers Also, the advantages of this method in comparison with the classical method of identification using added mass are considered, that are its versatility and ability to quickly configure and adapt for research and experimentation with different loudspeaker models and different types of transducers used in acoustics. Area of practical use of the research results: the proposed genetic loudspeaker model identification scheme can be directly applied on practice to speed up research and development tasks in electroacoustics and other related fields that require frequent experimentation with different types of transducer models. Innovative technological product: genetic algorithm based loudspeaker identification scheme that can be applied to identify various model of electrodynamic transducers. Scope of application of the innovative technological product: electroacoustics, loudspeaker design, audio system

The Use of Phononic Crystals to Design Piezoelectric Power Transducers

It was recently proposed that the lateral resonances around the working resonance band of ultrasonic piezoelectric sandwich transducers can be stopped by a periodic array of circular holes drilled along the main propagation direction (a phononic crystal). In this work, the performance of different transducer designs made with this procedure is tested using laser vibrometry, electric impedance tests and finite element models (FEM). It is shown that in terms of mechanical vibration amplitude and acoustic efficiency, the best design for physiotherapy applications is when both, the piezoceramic and an aluminum capsule are phononic structures. The procedure described here can be applied to the design of power ultrasonic devices, physiotherapy transducers and other external medical power ultrasound applications where piston-like vibration in a narrow band is required.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI).J.L.A. wishes to thank DGAPA-UNAM-PAPIIT for financial support through grant IN110817. F.M. wishes to thank to CICYT DPI2013-46915-C2-1-R and DPI2016-80254-R support. Finally, F.M. and J.L.A. thank the “Programa de Movilidad Académica de la Coordinación de la Investigación Científica-UNAM

Electromechanical characterization of ultrasonic NDE systems

An ultrasonic nondestructive evaluation (NDE) measurement system is a complex collection of many elements such as the pulser/receiver, the cabling, the transducers, and the material configuration being tested. To completely model an ultrasonic measurement system, a system model, called the electroacoustic measurement (EAM) model , was developed. This model allows one to analyze the measurement system at many different levels, ranging from individual details to the entire system itself. The EAM model has been implemented in software using the MATLAB development environment such that one has control over the specification of the detailed system components. On the other hand, the practical use of the EAM model for commercial systems, whose explicit internal construction details are not known, requires that the model be expressed in terms of elements that can either be obtained experimentally or modeled. Thus, the EAM model has also been characterized in terms of a small number of system parameters that can either be explicitly modeled or obtained from purely electrical measurements. This advance is important, since it lays the foundation for new, quantitative transducer characterization procedures and new methods for evaluating and compensating for system variabilities

Possibilities of Reliable Ultrasonic Detection of Subwavelength Pipework Cracks

An occurrence of cracks in pipework could lead to potentially very dangerous malfunction in some critical engineering systems such as power plants. There is a clear trend of replacing traditional manual testing with non-invasive in-situ methods that should detect crack formation in its early stage. Such as approach would enable replacing of unhealthy pipe components during the regular periodic outages. Ultrasonic testing is known to be a rather mature and reliable technology. However, it suffers from serious problems in detection of the cracks of subwavelength size. This paper attempts to soften aforementioned problems by investigating the influence of a duration of the unipolar excitation signal on the achieved resolution. In addition, the transducer input electricalimpedance of NDT transmitter was measured by using different excitation pulses and their levels and the results are compared with those obtained using traditional frequency sweeping method at low excitation levels. Finally, use of some advanced signal processing algorithms that might lead to the automatic detection of subwavelength voids, in scenarios with low signal-to-noise ratio, is discusse

Model idealnog električnog transformatora u sustavu prilagođenja impedancije piezoelektričnih hidroakustičkih pretvarača

The subject of this paper is matching electrical hydroacoustic piezoelectric transducers, by means of an electrical transformer and a LC transformer, to the wave resistance of an antenna electric cable, which is connected to transceiver sonar. By using the ideal transformer model and LC transformer, special formulas were gained, which enables the correct computing of elements necessary for performance and complete matching of electrical impedance and the phase angle.U radu se obrađuje prilagođenje električne impedancije hidroakustičkoga piezoelektričnog pretvarača pomoću električnog transformatora i LC transformatora na valni otpor električnog kabela antene spojenog na elektronički sustav primo/predaje sonara. Koristeći model idealnog električnog transformatora i električnog LC transformatora, dobivene su posebne formule koje omogućavaju točan izračun potrebnih elemenata za izvedbu i potpuno prilagođenje modula električne impedancije i faznog kuta

Ultrasonic system models and measurements

In this work ultrasonic models and measurements are used to characterize a number of the important elements of an ultrasonic measurement system as well as the entire system. Ultrasonic measurement models for predicting the response from reference reflectors are described, including a new ultrasonic measurement model recently developed to simulate the ultrasonic response of an infinitely long cylindrical cavity. The reference reflectors considered include spherical pores, flat-bottom holes and side-drilled holes, which are commonly used in nondestructive evaluation studies. These reflectors are employed in a series of modeling/experimental studies to assess where approximate and more exact scattering models are needed and to estimate the significance of beam variations over the reflector surface. Model-based simulated flaw responses are compared to experimentally determined flaw responses from these reference reflectors and the accuracy of the models is discussed.;The role that an ultrasonic piezoelectric transducer plays in an ultrasonic measurement system can be described in terms of the transducer\u27s input electrical impedance and its sensitivity. A new model-based method for simultaneously determining the impedance and sensitivity of commercial ultrasonic immersion transducers is developed. This method is based on a pulse-echo setup and relies only on electrical measurements. It is demonstrated that sensitivities obtained with this new method agree well with the sensitivities obtained using a more complex three-transducer method originally developed for lower-frequency acoustic transducers that has been used in many previous studies. The influence of the pulser/receiver settings on the transducer electrical impedance and sensitivity is also discussed. Cabling effects present are compensated for in the new pulse-echo method.;The transducer impedance and sensitivity measurements obtained using this new pulse-echo method are combined with measurements/models for all the other electrical elements in an ultrasonic measurement system to determine a system transfer function that characterizes the effect of all the electrical and electromechanical components in the system. It is shown that by combining the system transfer function with models of the acoustic/elastic process present in a measurement system it is possible to accurately simulate the output voltage of the entire ultrasonic measurement system

Model idealnog električnog transformatora u sustavu prilagođenja impedancije piezoelektričnih hidroakustičkih pretvarača

The subject of this paper is matching electrical hydroacoustic piezoelectric transducers, by means of an electrical transformer and a LC transformer, to the wave resistance of an antenna electric cable, which is connected to transceiver sonar. By using the ideal transformer model and LC transformer, special formulas were gained, which enables the correct computing of elements necessary for performance and complete matching of electrical impedance and the phase angle.U radu se obrađuje prilagođenje električne impedancije hidroakustičkoga piezoelektričnog pretvarača pomoću električnog transformatora i LC transformatora na valni otpor električnog kabela antene spojenog na elektronički sustav primo/predaje sonara. Koristeći model idealnog električnog transformatora i električnog LC transformatora, dobivene su posebne formule koje omogućavaju točan izračun potrebnih elemenata za izvedbu i potpuno prilagođenje modula električne impedancije i faznog kuta

An Alternative Approach to Determine the Dynamic Stiffness of Resilient Materials under Low Prestatic Load

Dynamic stiffness is a parameter of great importance for the assessment of the sound insulation properties of resilient materials commonly used under floating floors in dwellings. This work proposes a simplified approach that relies on an electro-mechanical circuit model for the determination of this parameter using a two-degree-of-freedom system of masses and springs. Unlike the method described in the standard ISO 9052-1, the proposed approach uses a single electrodynamic actuator both as an impulser and vibration sensor, thus reducing the instrumental requirements and yielding a more stable arrangement. By measuring the input electrical impedance of the mass-loaded actuator when coupled to a slab–material system it was possible to retrieve the mechanical mobility function thereof and thus obtain the dynamic stiffness of the material. Several materials were tested following the proposed approach, with results showing good agreement when compared to those obtained following the standardized procedure. In general, the preliminary research encourages the use of the proposed approach for characterization purposes

INFLUENCE OF PIEZOELECTRIC ANISOTROPY ON ELECTROMECHANICAL PERFORMANCE OF ULTRASOUND NDT PROBES AT ELEVATED TEMPERATURES

When designing an ultrasound non-destructive (NDT) probe for high temperature applications, one has to take into account a multitude of temperature induced effects, such as the temperature dependence of key physical properties of probe materials. In this paper, the significant influence of temperature change on piezoelectric properties and piezoelectric anisotropy, and thus on the ultrasound properties of the whole probe, is discussed theoretically. This is demonstrated within the thermodynamic Landau-Ginzburg-Devonshire (LGD) framework and the KLM model of equivalent circuits for two different piezoelectric, acoustically active probe materials from the same family - barium titanate and lead titanate. These two materials are model materials for the whole family of piezoelectric perovskites, including the commercially widely used PZT and relaxor ferroelectrics PMN-PT and PZN-PT