Key Engineering Materials Vols. 381-382

Abstract: It’s an important problem for power industry; energy industry, aviation and shipping to real-time measure the rotating blades’ tip clearance of engine. The conventional measurement techniques have different limitations. To achieve applied level for tip clearance measurement technique, according to the use request and application environment of tip clearance sensor, a new fiber-optic sensor was put forward to measure the blade tip radial clearance of engine in non-contact mode. The sensor was consist of single-bundle transmitting fiber in the center for laser beam delivery and three groups receiving fibers located in all around for collecting the scattered light. The sensor can not only eliminate the effect to measurement results of light source fluctuation and reflectivity variety of tip surface, but also reduce the effect of angle between the tip surface and sensor end face to measurement results. From the measurement results obtained from sensor on different clearance points, it proves that the sensor measuring system has well feasibility and reliability in blades tip clearance detection.

Abstract: This paper presents a nonlinear optimization design of microaccelerometer. The sensitivity rates with respect to the structural sizes, for example, length, width, and depth, are simulated before we start the optimal design. Four types of microaccelerometers are investigated that the maxima sensitivity and bandwidth are taken into the design specification. The results meet the requirement of large bandwidth successfully.

Abstract: After deriving the propagation formula of stress wave through incident bar, the measured signals both in horizontal impact test and drop impact tests are investigated with novel fiber Bragg grating sensors(FBGs). Especially those strain signals from FBGs which mounted on the surface of an incident bar are studied. The signals in impactor and the FBGs embedded in the composite material under similar test condition are compared. The dropping and impacting models have been setup. The experiment data measured in a lab are analyzed both in time-domain and in frequency domain. Those ultra-high frequency components in the above strain signals can not be obtained by current FBG measurement system due to frequency limit of the demodulation system. Further study to improve the frequency of demodulation system will be done in next step.

Abstract: Least squares support vector machine (LS-SVM) combined with niche genetic algorithm (NGA) are proposed for nonlinear sensor dynamic modeling. Compared with neural networks, the LS-SVM can overcome the shortcomings of local minima and over fitting, and has higher generalization performance. The sharing function based niche genetic algorithm is used to select the LS-SVM parameters automatically. The effectiveness and reliability of this method are demonstrated in two examples. The results show that this approach can escape from the blindness of man-made choice of LS-SVM parameters. It is still effective even if the sensor dynamic model is highly nonlinear.

Abstract: Some tags in the radio frequency identification (RFID) application based on the surface acoustic wave (SAW) technique often locate in the field of a transceiver simultaneously, leading to difficult identification. In this paper, the digital beamforming technique is applied to identify multiple SAW ID-tags to address difficulties in identification. The direction of arrivals (DOAs) are used to denote the locations of the tags and the particle swarm optimization (PSO) algorithm is suggested to find the optimal estimates of the DOAs. Once the DOAs are obtained, the array weights are then formed and the signals of tags are recovered to implement decoding. The experiment results show that a good identification of multiple SAW ID-tags is achieved.

Abstract: A new distributed optical fiber pipeline leakage detection technology based on Mach-Zehnder optical fiber interferometer theory is put forward. When using this technology, an optical fiber cable is laid along the pipeline. Noise from leaking point on the pipeline can be acquired by the optical fiber vibration sensor which was composed of three single mode optical fibers, thus, leakage occurred on the pipeline can be detected in real time. The detection principle and system construction are explained and in-site testing data is analyzed. With principle analysis and experimental results, it is demonstrated that the detection system’s measuring sensitivity and location accuracy for detecting leakage are high when adopting this technology.

Abstract: In electrical discharge machining (EDM), an electrical discharge occurs between a tool electrode and a work-piece, and removal of materials is carried out by vaporized explosion between the electrode and the work-piece. However, the mechanism of material removal in EDM is not well understood. In order to clarify this issue, the acoustic emission (AE) method has been applied to examine the force of explosion, and the Schlieren visualization method has been applied to observe the explosion. In this study, we investigate the effect of discharge current behavior on the occurrence of the AE waves by means of an optical fiber vibration sensor.

Abstract: In this paper, a controlled oscillation using the levitation mass method (LMM) for material with nonlinear viscoelasticity is proposed. Since LMM is a very accurate and efficient method of measuring a varying force, it has a possibility to apply to the material tester. For LMM, system identification process is introduced to grasp the nonlinear components of the restoring force. The process consists of the experiment and frequency analysis for higher modes which originate for the nonlinear restoring force. The input signal is then derived based on the identification results. By adding the proposed identification process to LMM, the arbitrary waveform of the force can be investigated even in the open-loop excitation. The effectiveness of the proposed oscillation method is verified through the LMM-based experiments.

Abstract: In the current space program, astronaut body mass onboard spacecraft, including the International Space Station (ISS) is measured with spring-mass device. We propose a new device “Space Scale” with laser interferometry acceleration measurement and an inline force sensor with a bungee cord. This paper describes concept of Space Scale and its accuracy estimation by ground model test. Accuracy obtained in this ground test was –0.293 %, of which force sensor contributed most to error.

Abstract: State of the art in Coriolis mass flow metering is the single straight tube oscillating in resonance and actuated by one electromagnetic actuator. The difference in time of two electro-magnetic sensors measuring the velocity of the vibrating tube at the up- and downstream side of the tube is directly proportional to mass flow. By using a lumped parameter model consisting of two coupled oscillating systems that represent the oscillation in the first and second eigenmode one can derive the characteristics of the device in terms of zero and sensitivity, two important parameters in today’s mass flowmeters. In [1, 2] these parameters are calculated from measurements obtained by additionally stimulating the device in the second eigenmode in a cyclic procedure. As only measurements in steady state can be used, the procedure is time consuming and up to now not generally applicable. However, these shortcomings can be overcome by using a new control strategy. In this strategy the oscillation of the first and second eigenmode is assigned in terms of amplitude, frequency and phase via a so called trajectory generator and is realized by a flatness-based control scheme derived from the lumped parameter model. In the paper we will present a method to identify the parameters zero and sensitivity without the need for a cyclic operation of the device.