Contactless Displacement Sensors Research Articles

Contactless Deformation Monitoring of Bridges with Spatio-Temporal Resolution: Profile Scanning and Microwave Interferometry

Against the background of an aging infrastructure, the condition assessment process of existing bridges is becoming an ever more challenging task for structural engineers. Short-term measurements and structural monitoring are valuable tools that can lead to a more accurate assessment of the remaining service life of structures. In this context, contactless sensors have great potential, as a wide range of applications can already be covered with relatively little effort and without having to interrupt traffic. In particular, profile scanning and microwave interferometry, have become increasingly important in the research field of bridge measurement and monitoring in recent years. In contrast to other contactless displacement sensors, both technologies enable a spatially distributed detection of absolute structural displacements. In addition, their high sampling rate enables the detection of the dynamic structural behaviour. This paper analyses the two sensor types in detail and discusses their advantages and disadvantages for the deformation monitoring of bridges. It focuses on a conceptual comparison between the two technologies and then discusses the main challenges related to their application in real-world structures in operation, highlighting the respective limitations of both sensors. The findings are illustrated with measurement results at a railway bridge in operation.

Experimental and theoretical research of continuous motion of rotor on anisotropic gapped elastic support

Kinematic and dynamic features of flexible rotor rolling of an unlubricated uneven-stiffness gapped support are shown with the help of a theoretical model and full-scale tests. A combination of original approaches and well-known analytical and experimental methods is used. In particular, the motion equations are Lagrangian, derived in complex and complex-conjugate coordinates, and their solutions are sought in the exponential form, by excluding contact forces from consideration and by introducing a small parameter. Vibration measurements are not made on the rig frame using accelerometers, but at the source of vibration, i.e. by direct tracking of the rotor axle by a pair of eddy-current contactless displacement sensors installed in a XY configuration. Hence, the preciseness of the experimental data does not depend on the mechanical conductivity of the parts between the source rotor and the receiver sensors. As a result, the frequency, amplitude and existence domain of retrograde precession are reliably determined, and a conclusion is drawn that rolling under a certain combination of parameters is impossible in principle.

A Method Using Optical Contactless Displacement Sensors to Measure Vibration Stress of Small-Bore Piping.

In nuclear power plants, vibration stress of piping is frequently evaluated to prevent fatigue failure. A simple and fast measurement method is attractive to evaluate many piping systems efficiently. In this study, a method to measure the vibration stress using optical contactless displacement sensors was proposed, the prototype instrument was developed, and the instrument practicality for the method was verified. In the proposed method, light emitting diodes (LEDs) were used as measurement sensors and the vibration stress was estimated by measuring the deformation geometry of the piping caused by oscillation, which was measured as the piping curvature radius. The method provided fast and simple vibration estimates for small-bore piping. Its verification and practicality were confirmed by vibration tests using a test pipe and mock-up piping. The stress measured by both the proposed method and an accurate conventional method using strain gauges were in agreement, and it was concluded that the proposed method could be used for actual plant piping systems.

A Method Using Multiple Contactless Displacement Sensors to Evaluate Vibrational Stress of Small-Bore Piping

In this study, a method using optical contactless displacement sensors to evaluate vibrational stress was proposed. As sensors, light-emitting diodes were used. The values measured with multiple displacement sensors were used in the proposed method to approximately calculate deformation shape, that is, curvature radius which occurs within a relatively narrow area of anything to be measured, and then the vibrational stress was obtained using the curvature radius. The vibrational stress was compared with the stress obtained by the conventional method using strain gauges, and the applicability of the proposed method was verified. Furthermore, the measurement accuracy was discussed from a sensitivity analysis with regard to the signal-to-noise ratio during the measurements.

Modelling and characteristic analysis of a displacement sensor with liftoff compensation

PurposeThe purpose of this paper is to present a magnetic contactless displacement sensor with liftoff compensation. The sensor consists of two‐axis Hall sensor, moving permanent magnet (PM) and ferromagnetic substrate which is considered as a magnetic flux concentrator.Design/methodology/approachThe two Hall‐effect sensors are used to detect the BX and BY induced by the moving PM. The BX and BY curves reflect the nature of the liftoff and the displacement of the inducing PM, respectively. Then the model of the displacement sensor, based on the facing current method, is constructed. Finally, the finite element method is used to compute the characteristics of BX and BY.FindingsThe BY curve can be corrected according to the liftoff distance of Hall‐effect sensor distinguished by the BX trough value. Therefore, the influence of the liftoff on the output signal can be eliminated when BY curve is corrected.Originality/valueThe paper focused on the design of a contactless displacement sensor with compensated liftoff performance for the control measurement technology in general and for automotive engineering in particular.

レーザー変位計を用いた小口径配管の振動応力計測方法の開発(保全・設備診断技術,<特集>第13回動力・エネルギー技術シンポジウム)

In the nuclear power plant, many small-bore piping are near vibrational sources like pumps, and it is important to evaluate vibrational stress of the piping efficiently to prevent the fatigue failure. We developed a new method to evaluate vibrational stress using displacements measured by multiple contactless displacement sensors. The purpose of this study is to verify the applicability of the proposed method by vibration tests with a pipe. In these tests, the stress evaluated by this method was compared with the stress measured by strain gauges. As the results, the evaluated stress was in good agreement with the measured stress, but this method has some errors which are negligible comparing to endurance limit of failure. Therefore the method we developed is applicable to measure vibrational stress of small-bore piping.

A104 レーザー変位計を用いた小口径配管の振動応力計測方法の開発(検査・モニタリング-1(疲労,SCC,熱流動),OS6 保全・設備診断技術(1),一般講演,地球温暖化防止と動力エネルギー技術)

In the nuclear power plant, where many small-bore piping connected to vibrational sources like pumps, it is important to evaluate vibrational stress efficiently to keep the plant operating safely. The purpose of this study is to develop a method to measure vibrational stress efficiently by using multiple contactless displacement sensors. The applicability of the method is verified by vibration tests with a pipe. In the vibration tests, the stress calculated by the proposed method was compared with the stress measured by strain gauges. As the results, the calculated stress was in good agreement with the measured stress though having some errors which are negligible comparing to endurance limit of failure. Therefore the method we developed is applicable to measure vibrational stress of small-bore piping.

IMS-Displacement Sensors (Inductive Magnetic Saturation)

More and more automotive applications require exact position sensing. Today resistive potentiometers are the most frequently used sensors. For reasons of reliability, there are increasing demands to replace these kinds of sensors by contactless displacement sensors, without increasing the costs.