Papers by Author: Guo Xiong Zhang

Abstract: A difference-frequency mixer based on exclusive-or gates with a filter at the output, which processes a variable frequency input signal and a reference input signal (produced by measurement system) to develop an output signal representative of the frequency difference between the two input signals, was studied in theory and simulation experiments. Digital difference-frequency mixers of this kind can be used in the output signal measurement of resonator-based sensors for high resolution and short measure time.

Abstract: The paper presents the measurement system of the air plane fuel mass consisting of cylinder shell resonating density meter and double cylinders capacitance level meter. The finite element analysis method of ANSYS10.0 is used to analyze the performance of cylinder shell resonator density meter and double cylinders capacitance fuel level sensor. On the base of simulation, the cylinder shell is 45mm in length, 9mm in radius, and 0.08mm in thickness, the material is 3J53; the double cylinders capacitance is 8mm in inside diameter, 23.6mm in outside diameter, and 550 mm in length. The experiments show the uncertainty of cylinder shell resonating density meter is only 0.12%, the uncertainty of double cylinders capacitance level meter is only 0.2%, and the uncertainty of the fuel mass measurement system is 0.4%.

Abstract: A simple and practical calibration method is proposed to calibrate the articulated arm flexible CMM. Firstly, a quasi-spherical coordinate system is put forward based on DH method according to the special structure of the articulated arm flexible CMM. This calibration method is presented to determine and separate machine parameters and errors in a creative way based on multiple reversal technology. Experiments were carried out for a Faro Platinum 4ft articulated arm CMM by using a Chameleon 9159 5Q orthogonal CMM. The results prove the feasibility of the proposed method for articulated arm CMM calibration, and all parameters are separated completely. It provides a theoretical base for introducing error compensation and improves the measurement accuracy of the articulated arm CMM.

Abstract: With the development of modern industry, the consciousness of quality monitoring increases rapidly. The requirements to the dimensional control and profile monitoring of the products including the mechanical, optical and electric ones become higher and higher. New, non-contact and convenient instruments are needed to enable people to evaluate their products. A new type of dynamic active confocal probe is developed in this paper. The key point of this new method is that the displacement measurement of the vibrating lens located on the tuning fork is converted to time difference measurement, which is much simpler and assures higher accuracy in measurement. System structure and improvement, electric circuit and signal processing system are discussed. Experimental studies of the probe performance and analyses of the experimental results are presented.

Abstract: This paper describes a micro-target semiautomatic assembly system used in ICF. In the system two halves of a cylindrical gold hohlraum (1.6 mm long by 0.8 mm in diameter) and a microsphere capsule (about 0.2 mm in diameter) are assembled. CCD cameras are applied to monitor the process of closed loop assembly.

Abstract: CCD camera is used in the liquid signature analyzer system to capture images of the liquid drop of the tested sample. The digital image processing work is presented. CCD camera records the variation of the liquid drop during growth. The outline information of the drop is available through image processing. The instantaneous volume of the liquid drop can be gained through mathematical calculation. With the use of CCD camera, the information of the tested sample we can get during the measurement is enhanced. The function of the liquid signature analyzer is enriched and the discrimination ability of this technology is improved.

Abstract: A portable three-dimensional vision coordinate measuring system is proposed in this paper. It consists of a light pen, a CCD camera and a laptop computer. The light pen is a hand-held probe with three point light sources using LEDs and a spherical touch stylus arranged in one line. The CCD camera takes the image of LEDs on the light pen and the 3D coordinates of measured point at the center of touch stylus are obtained by computing the positions of LEDs in the image when the probe contacts the object surface. The equations of the vision measurement system are derived by using perspective of three collinear points and spatial analytic geometry. The measuring device can be set up easily on an industrial site and the measurement is convenient. The object surface can be simple, complex, or hidden from the view of camera. The effectiveness of the mathematical model and validity of the measuring system are confirmed by experiments.

Abstract: An instrumental method for measuring the properties of liquids has been developed. The instrument, called the fiber-capacitive drop analyzer (FCDA), is based on a specially designed drop sensor by means of the fiber drop analyzing technology and the capacitive drop analyzing technology, and produces a volume-based fiber drop trace (VFDT), which shows the relation between the light intensity passing through the liquid drop and the instant drop volume. Preliminary experiments have been carried out and these prove that VFDT externalizes the overall properties of tested liquids and is suitable for fine discrimination among different kinds of liquids. In this paper, a multi-wavelength drop analysis (MWDA) method is described. In this case, the light source of the FCDA is developed from a single wavelength to a multi-wavelength. A special filter is employed to sort out the signals from the mixed multi-wavelength signals and it becomes possible to get two or three VFDT with different light wavelength at the same time. As one knows, a material will absorb the light on certain wavelengths. It means that, for a mixed liquid, one can get different VFDTs by MWDA at the same time. By this way, the resolution capability of a FCDA is enhanced very much due to more information including in those VFDTs. A special signal process circuit, the key technology of the MWDA, is described in this paper. The test results show that the new circuit had satisfied the MWDA method well and will be very useful to an instrument of the FCDA with MWDA.

Abstract: A TiAl sheet fabrication technique from Ti/Al foils was studied experimentally. Firstly, the reaction sequence between Ti and Al foils were studied with DSC and then a three stage solid transformations processing was carried out. At the first stage, Al diffused into Ti foils and formed Al3Ti. The heating temperature was selected based on a ruler that the pure Al was consumed by solid diffusion with a short time and avoiding the melting of Al. The resulted microstructure consists of pure Ti and Al3Ti. At the second stage, part of Al in Al3Ti diffused into pure Ti and formed the high temperature phase. At the third stage, the sample was heated into the high temperature -phase zone and hold a given time and then cooling with the furnace. A full density γ-TiAl based alloy sheet with lamellar microstructure was successfully fabricated under above processing. The lamellar orientations are aligned around 0-45o compared to the longitudinal direction of the sheet.

Abstract: Reverse engineering of free-form surfaces is one of the most challenging technologies in advanced manufacturing. With the development of industry more and more sculptured surfaces, such as molds and turbine blades, are required to measure quickly and accurately. Optical non-contact probes possess many advantages, such as high speed, no measuring force, in comparison with contact ones. The ability of stereovision probe with CCD cameras in gathering a large amount of information simultaneously makes it the most popularly used one in sculptured surface measurements. So based on the laser triangular principle, a measuring and testing device with two CCD cameras was designed, and its accuracy was analyzed. With a virtual 3D target in form of a grid plate, all the intrinsic and extrinsic parameters of CCD camera including the uncertainty of image scale factor and optical center of camera can be readily calibrated. In order to obtain all the required data with high accuracy in a short time, the curvature-based adaptive sampling strategy is presented. Due to huge amount of arbitrary scattered points, the Delaunay triangular division and Bezier interpolation and NURBS interpolation are applied to get a continuous surface.