Key Engineering Materials Vols. 381-382

Abstract: The airport runway frictional coefficient is one of the most important factors which affects the safety of airplane's landings and take-offs under the rain or snow weather. In this paper, each kind of factor which affects the precision of frictional coefficient measurement under the bad condition such as snow and ice covered, rubber pollution and wet runway have been analyzed, and then establish the model of frictional coefficient measurement. A new strategy which uses variable gain recursion least square algorithm has been used to eliminate the error caused by the rugged runway in the high speed measurement process, so as to assure system anti-jamming ability and fast track capacity. Use the vertical pressure pertinence analysis to eliminate the errors caused by the runway surfacing joint.

Abstract: A fan-shaped laser beam scanning measuring system based on the triangulation principle, was newly developed in this study to measure simultaneously the flatness and the surface roughness of a surface plate with good reflectivity after a suitable calibration. The developed system mainly consists of a micro-focus fan-shaped line laser, an image processing system, a PC-based 3-axis machine, and a PC. The height value of the object can be calculated, based on the offset between the position projected onto the object and the position projected onto the platform, after carrying out the height calibration with gauge blocks. According to the scattering theorem, a correlation between the surface roughness of the test object measured with a precision stylus instrument and the average fringe width projected onto the test object surface, has been constructed.

Abstract: To meet the requirements of next generation Geometrical Product Specification and Verification (GPS), a surface texture information system integrated with AutoCAD is developed. The information system mainly consists of three parts: a surface texture database containing large amount of surface texture specification information, inference algorithms and interfaces with AutoCAD, so that unambiguous, explicit and complete specification for design, manufacture and verification of surface texture can be provided in AutoCAD for function assurance.

Abstract: This paper describes the software gauge data for surface texture standard using the non-causal 2D auto-regressive model (A-R model). This model can provide with 3D irregular surface topography and intentional geometrical characteristics from specified surface texture parameters. The measurement area consists of a periodical combination of the generated sampling area data. The surface roughness parameters introduced from the gauge data on a defined evaluation area can be insensitive to size and location of the evaluation area size. Adequate measuring conditions to utilize the surface material measures were investigated and then the evaluation area and sampling distance for areal profiling by a stylus instrument were clarified.

Abstract: In order to improve the displacement measurement accuracy of the laser diode self-mixing interference (SMI), phase measurement method is introduced in the SMI signal analysis. In this paper, three modulation technique have been proposed: injection current modulation, external cavity length modulation and sinusoidal phase modulation. Measurement principle of the three modulation techinque are briefly explained. Design of the experimental system, measurement results of micro-displacement will be reported.

Abstract: This paper presents a novel laser feedback interferometer for metrology of large range displacement. A Birefringence-Zeeman dual frequency laser is applied in the system. Due to its strong optical feedback effects, the intensity modulation curves of the two polarized lights will have a zero intensity part in a period. A quartz crystal is used in the external feedback cavity as a birefringent element. And a phase difference between the two lights can be adjusted to π/2. Thus, the intensity modulation curves in a period can be divided into four polarization zones with equal width. When the displacement of the object to be measured is produced, the four polarization zones will appear in sequence. According to the appearance order of the four zones, the direction of the displacement can be discriminated without ambiguity and the resolution of the system can be greatly increased. It is confirmed that the laser feedback interferometer has a resolution of 79.1nm and with a linearity of 0.01% over the whole measurement range of 15mm.

Abstract: A new approach is found to eliminate the nonlinearity of heterodyne interferometer. It uses a simple phase compensation system by rotating a polarizer which is set up before the detector in the interferometer. This method can be used in most science researches and the industry precision nanometer measurement, and it is valid for all nonlinearity errors whether it is a first-order or a higher-order error, or caused by any reasons.

Abstract: In this paper, a perpendicularly overlapped transient thermal grating (TTG) method is proposed to characterize the weakly absorptive or poorly reflective materials. Based on the Kirchhoff’s law and thermal elastic theory, the theoretical distribution of the diffraction light in space, which modulated by the overlapped TTG method and TTG method, have been given. As the simulation results shows, the diffraction ability of the perpendicularly overlapped TTG is much better than that of the TTG method, and much suitable to characterize the thermal properties of opaque sample with weak absorptivity or poor reflectivity.

Abstract: Null compensator method is a popular aspheric surface testing method. However null compensator has the characteristics of complex structure, high price and poor universal property. This paper proposed to test aspheric surface by a partial compensation lens (PCL) to overcome the defect. This novel PCL method is designed to partially compensate the wave aberration caused by the aspheric surface, which allow some residual wave aberration exists. Research was conducted on measurement principle, design method of PCL. The experiment results show the feasibility and validity of this method.

Abstract: In laser-scanning measurement of cylindrical objects extremely complex interfering signals occur. They are due to superimposition of: reflected, unobstructed and scattered light. The proportions between these components vary in time and also the total intensity distribution changes. The considerations applying Fraunhofer theory are static and fragmentary, and may be concluded that the existing solutions for diffraction of 3D bodies do not fit to engineering applications. Having the above in view, the close analysis of detector signal was carried out. The obtained differential intensity characteristics allow to determine the important metrological qualities of diffraction field.