Key Engineering Materials Vols. 295-296

Abstract: A three-dimensional profile measurement system based on a projection coded grating technique is presented. The system uses a designing and decoding technique for grey coded gratings. The coded grating has black, white and grey stripes. The period triples a conventional grating. It greatly increases the height measuring range without any decrease in stripe separation. The shape of object can be obtained from only one grating image. The system is suitable for instantaneous measurement of moving objects including human face. The technique proposed permits rapid 3D measurement and no moving parts are involved in the system. The hardware is relatively simple. Special data processing software is developed. Results of a practical example confirm the effectiveness of the proposed method.

Abstract: Based on the differential confocal microscopy principle, a non-scanning 3D profile detecting system is proposed. A 2D light source array produced by micro-optic components is used to form a parallel micro-confocal system. The whole field detecting of the measuring plane is realized. The reflected light beam is divided into two paths. Two CCD cameras work together to detect the facula array in a differential arrangement. A differential algorithm of facula intensity is used. The noise and the shift of light source can be avoided effectively. Using the linearity characteristic of the differential confocal system, the high axial resolution is achieved at a larger sampling interval. The measuring efficiency and accuracy can be increased. The construction and working principle of the 3D parallel detecting system and the 3D profile reconstruction method are investigated. Experiment results agree with the ones of theory analysis. It indicates that the differential method is applicable for non-scanning 3D profile detection.

Abstract: Automatic recognition of road distresses is of considerable interest since it facilitates road maintenance. We propose the use of artificial life for pavement distress survey. All artificial organisms in the artificial life algorithm exhibit the principle of cooperation which can be found in computer virtues and the hunting process of predators. Experimental results demonstrate that the proposed approach has a strong effect on noise removal such as elimination of oil stains and removal of dark spots which is one of the most difficult problems in pavement distress survey

Abstract: The coincidence of vortices generated by a bluff body in a gaseous flow (Karman vortex street) with an ultrasonic beam crossing these vortices raises a lot of questions concerning physics and signal processing. The ultrasonic signal will be complex modulated. The spectrum of the resulted signal shows the carrier frequency of ultrasound and two narrow sidebands with the information about the modulation. For further signal processing the carrier frequency must be filtered. The carrier frequency can be shifted to zero by digital processing and undersampling the signal by an integer multiple. Then the sideband with its low frequency range can be analysed. The real and imaginary parts of the signal can be determined by sampling the signal shifted by 90 degrees (Hilbert transform). Even the 90 degree shifted angle can be measured by undersampling. The sensitivity of the vortex meter depends on the bluff body size. A simple relation between the bluff body dimension and the sensitivity, the vortex frequency, respectively, is shown.

Abstract: Fluid flow diverter serves as an essential element in high accuracy liquid flow calibration facility using a static weighing gravimetric system coupled with a flying-start-and-finish mechanism. For such flow system, stability and patterns of flow that passing through the draining nozzle and diverting module influence the accuracy of flow rate measurement. Consequently, the design and implementation of a diverter mechanism with feeding pipe section contribute dearly to the total measurement uncertainty of a standard calibration facility. In this research, a draining nozzle that changes from circular cross section to rectangular was specially developed to provide fluent flow transition. To facilitate the design process, the computational fluid dynamics (CFD) was introduced that effectively reduced the time consumption for prototype construction and test. The selected design exhibited symmetric and stable flow patterns in the desired operational flow range.

Abstract: This paper is resulted from a jetting force measurement experiment. The principle and the mathematical model of a jetting force measurement system are introduced. The characteristics of the measured data and the algorithm of extracting the jetting force are examined. The experimental results verify the algorithm and the theoretical results by use of system identification techniques.

Abstract: The purpose of this paper is to analyze and compare the dynamic characteristics of various structure pressure sensors using the Improved Pressure Square Wave Generator (IPSWG). The developed IPSWG is a signal generator that creates pressure square waves as an excitation source. The dynamic characteristics of pressure sensor in hydraulic systems can be measured and evaluated effectively due to the high excitation energy. The method is also useful for dynamic testing and characterization for a high frequency range, which cannot be performed by the traditional methods, such as the hammer kit excitation, sweeping frequency pressure wave, and random frequency wave. Result shows that piezoelectric sensors (quartz) have a largest gain margin and overshoot. The strain gauge sensor has a smaller gain margin and overshoot. The piezoelectric sensor is more suitable for measuring dynamic pressure.

Abstract: A high sensitivity pressure sensing system with a fiber Bragg grating (FBG) using the transverse strain characteristic of a straight bourdon tube (SBT) is presented and demonstrated for the first time to our knowledge. The transverse strain of the SBT makes the FBG tensioned. The pressure can be determined by measuring the shift of the Bragg wavelength. The experimentally obtained results indicate that the shift of the Bragg wavelength changes linearly with the applied pressure and the sensitive coefficients of pressure are approximately 6.22x10-3MPa-1. This represents a sensitivity value approximately 9.66x10-3pm/Pa. The pressure sensing system shows little hysteresis error.

Abstract: The design of a polarized optical pressure fiber sensor system is presented. The system mainly consists of a laser, a birefringent crystal, a quarter wave plate, two polarizers, a sensing element and two photodetectors. The design of the sensing element is based on the photo-elastic effect. This type of sensor can be used to detect pressure, force and weight of an object. In addition, the sensor can be used to detect and to monitor the condition of overload of a vehicle real time and on line.

Abstract: It is hard to ensure the survival of sensors for jet flow pressure measurement for several hundred microseconds to approximately 20 milliseconds under a severe radiation condition with a dose rate at 1013 rad (Si)/s and a strong explosion shock. A novel method is proposed to effectively solve the problem. The method is based on the plastic deformation principle of metal material and is based on the use of a pressure threshold. The method is particularly useful for large scale chemical explosion tests.