Papers by Keyword: Piezoelectric Sensors

Abstract: In this paper, the propagation characteristics of Lamb waves activated and collected by piezoelectric sensors bonded on an aluminum panel were investigated both theoretically and experimentally on different bonding cases. The bonding layer is an intermedium of energy transmission between structure and sensor. The bonding quality heavily effects on the lamb propagation characteristics, including frequency dispersion, mode conversion, and signal amplitude. In particular, the variation of the surface strain with frequency for symmetric lamb mode was studied in different bonding quality. A sensor bonding quality evaluation method based on frequency response characteristics of the surface strain was developed to compensate the sensor network. The proposed approach can provide a useful reference for structural health monitoring strategy formulation.

Abstract: This paper presents the results of an experimental study on the application of piezoelectric dynamic strain sensors for monitoring the crack growth in fracture mechanics specimens. The performance of the piezoelectric sensors was assessed through fatigue crack propagation tests in three point bend (TPB) specimens and compact tension (CT) specimens. Piezoelectric sensors of lead zirconate titanate (PZT) were placed close to the crack edge of TPB specimens and piezoelectric polyvinilidene fluoride polymer (PVDF) was bonded to the back face of CT specimens. The piezoelectric sensors detect the crack growth by monitoring changes in the dynamic strain field of the specimen. In its simplest mode, the piezoelectric sensors behave like dynamic strain gages, with the main advantage of having a high sensitivity which allows detection of lower strain levels and lower increase in crack length.

Abstract: The ideal of using air suspension is to reduce the movement friction of measurement system, since of the air suspension structure, the dynamic balance precision of rotating parts for measurement was improved. The use of air suspension measurement system to measure the deviation of the workpiece which rotating around a fixed axis is more efficient and convenient.

Abstract: The paper presents some results of research on the Weight-in-motion (WIM) system. The device is used for identification of loads on the road surface generated by traveling vehicles. The proposed approach utilizes the piezoelectric measurement techniques to monitor strain development in a deformable body and eventually these measurements are used for tire-pavement load identification. An advantage of the proposed concept is that no additional limitation for a vehicle velocity and direction is required in order to make the measurement feasible. The device allow to identify many parameters which can be stored for statistical and planning purposes. When an overload or an exceed in speed limit is detected the data can be sent for penalization purposes. The research includes a computer simulation of the bending plate detector using the Finite Element Method (FEM). Its objective is to validate the concept as well as to test some factors which are important with respect to the proposed load identification methodology. An experimental research involved field tests on the WIM system using a bending plate detector and inductive loops to detect a vehicle.

Abstract: Micro-Vibrations, generally defined as low amplitude vibrations at frequencies up to 1 kHz, are now of critical importance in a number of areas. One such area is onboard spacecraft carrying sensitive payloads where the micro-vibrations are caused by the operation of other equipment. In this paper a rectangular simply supported flexible panel is considered. The equipments are located on this panel as lumped masses and the micro-vibrations are induced by some concentrated forces. The piezoelectric layers are attached on both sides of the panel as sensors and actuators. The governing equations of motion are derived based on Lagrange-Rayleigh-Ritz method. An adaptive control scheme is applied to reduce the panel vibrations. Finally the simulation results show the advantages of the adaptive control algorithm.

Abstract: This paper mainly deals with the problem of oil pipeline leak and difficult to detect its location, combining the trait of our country’s oil pipeline, researching the leak detection and location based on the PVDF piezoelectric sensors. This paper firstly describes the domestic status of pipeline leak detection, and then gives a brief introduction for the PVDF piezoelectric film, finally discusses the pipeline leak detection and location system based on PVDF piezoelectric sensors. Experiments show that the use of PVDF piezoelectric sensors on pipeline leak detection, the leak can be correctly identified, and improving the detection sensitivity and leak resolution, effectively reducing the false alarm rate.

Abstract: Some applications, like force feedback joystick, require force measurement with high stiffness sensor to limit handle oscillations. In this way, this article presents an original technology to measure static force using the resonance frequency variation principle of a piezoelectric actuator subject to preload variation. We present in a first part comparison of various involved technologies to justify our choice (stiffness, inertia.....). The second part deals with the analytical modelling by variational principle of Langevin transducer. A comparison with the numerical FEM results is performed. Experimental results are then reached to validate the detailed concept. They demonstrate the potentiality of static force measurement with classical resonant structure like Langevin transducer with laboratory instruments. A last part is dedicated to the definition of an electronic to supply the sensor and to treat the measure. First experimental results are presented in an open loop electronic power supply configuration.

Abstract: This study validates an adaptive control algorithm capable of compensating for online sensor failure. Online failure is a relevant problem when considering actively damped, multi-story smart buildings experiencing a disturbance event. In recent years, Artificial Neural Networks (ANNs) have proven very efficient in pattern classification and control applications. In this study, the unique application of ANNs involving Radial Basis Functions (RBFs) combined with H∞ optimal control has demonstrated three significant characteristic advantages: (1) real time adaptability, (2) optimal convergence and computation time, and (3) most importantly, no offline training. The novelty of the proposed controller is elucidated by performing disturbance rejection tests involving a scaled two degree of freedom shear frame subjected to a combined H∞ and ANN control. A bench scale structural model is instrumented with piezoelectric sensors and actuators. After the onset of a first mode disturbance, the structural frame is subjected to a complete sensor failure. The proposed controller is shown to enhance the performance of a baseline H∞ controller in the presence of sensor failure.

Abstract: This paper presents novel structural health monitoring techniques for critical members of civil structures using electro-mechanical impedance sensors. The basic concept of this technique is to monitor critical locations of a structure for changes in structural impedance that would indicate imminent damage. In this paper, principal hardware and software issues on this topic are reviewed. An active sensing node incorporating on-board microprocessor and radio frequency telemetry is introduced in a sense of tailoring wireless sensing technology to the impedance method. A data compression algorithm using a principal component analysis is embedded into the on-board chip of the active sensing node. Finally, a method for compensating the temperature effects on the impedance measurements using cross-correlation analysis with effective frequency shifts is presented.

Abstract: This study aims at identifying the modal characteristics and their uncertainties for a smart composite beam. The problem is addressed via Vector AutoRegressive with eXogenous excitation (VARX) models. The advantages of VARX modeling include simplicity of implementation, high accuracy, parsimony of representation, and capability of handling modal uncertainties. Two different approaches to assess the modal parameter uncertainties are investigated. The first is based upon linearizing the function that relates the VARX model parameters with the modal parameters, whereas the second is based upon computer simulations using the Monte Carlo and the bootstrap schemes. The results indicate that VARX modeling captures the system dynamics and provides accurate modal parameters with tight confidence intervals.