Liangzhou Chen

Prediction of Surface Topography at the End of Sliding Running-In Wear Based on Areal Surface Parameters

Running in is a complex process, and it significantly influences the performance and service life of wear components as the initial phase of the entire wear process. Surface topography is an important feature of wear components. Therefore, it is reasonable to investigate the running-in process with the help of surface topography for improvement. Because the surface roughness after running in is independent of the nature of initial roughness, it is difficult to predict the surface topography after running in based on unworn surface topography. Aiming to build a connection of surface topographies before and after the running-in process, a black-box model predicting surface topography after the running-in process was established based on least-squares support vector machine (LS-SVM), and the areal surface evaluation parameters were adopted as model variables. To increase the adaptability of the predictive model, the main factors of the work condition were also taken into consideration. The prediction effect and sensitivity of the model were tested and analyzed. The analysis indicates that the hybrid property of surface topographies before and after running in is closely related. Moreover, the surface topography after running in is influenced more by the initial surface topography than by the work condition.

A Novel White Light Interference Based AFM Head

A novel atomic force microscope (AFM) head based on white light interference (WLI) is developed for nanoscale surface measurement. In this head, instead of an optical beam deflection (OBD) technique for AFM probe position, WLI fringes on the surface of the probe cantilever are analyzed for probe position. The probe adjustment mechanism is designed, an algorithm based on wavelet transform and Hilbert transform is presented for accurate zero-order fringe positioning, and a calibration method is developed for the relationship between the position of the interference fringes on the surface of the probe cantilever and the vertical displacement of the probe. By these approaches, advantage of high vertical resolution of WLI is combined with that of high horizontal resolution of atomic force probe for nanometer resolution surface measurement. Experiments have been carried out to verify the feasibility and accuracy of the head for AFM measurement. And compared with a commercial AFM, 3-D measurement results of a standard grating prove that the measurement speed of proposed AFM head is 22% faster.

A new alpha seeding method for support vector machine training

In order to get good hyperparameters of SVM, user needs to conduct extensive cross-validation such as leave-one-out (LOO) cross-validation. Alpha seeding is often used to reduce the cost of SVM training. Compared with the existing schemes of alpha seeding, a new efficient alpha seeding method is proposed. Through some examples, its good performance has been proved. Interpretation from both geometrical and mathematical view is also given.

3D measurement based on phase-shift and self-calibration

Non-contact three-dimension (3D) measurement technology has developed rapidly. Digital grating projection is regarded as the best prospect one. There are many problems, such as low accuracy, which have not been solved yet. Based on digital grating phase-shift, and combed with height-phase mapping and self lattice calibrating, a new 3D measurement method has been proposed. With little geometric constraints to digital grating and CCD, the measurement system is more feasible, which can be used to realize the accurate measurement and reconstruction according to the 3D information from measured object. By applying the method proposed to a reference object, the experience has lead to good result which shows that the new method is efficient and precision.

A New Grating Non-Diffracting Structured Light for Three Dimensional Shape Measurement

A new method of actualizing grating non-diffracting structured light (GNSL) is proposed. The GNSL holds characters of long focal-depth, narrow strip-width, steady light field and constant light intensity in certain rang etc. Based on precise triangular-section prism, an optical system is designed and actualized experimentally. With theory analysis and calculation to the optical system, the distribution of the light intensity is simulated in non-diffracting range. Experiment results show that simulation is in good agreement with the theory calculation. According to system parameters, GNSL with 18um strip-width and 57cm non-diffracting range is produced in experimental system. Compared with traditional projected light source, GNSL has advantages of high resolution and high precision in the application of three dimensions (3D) shape measurement. By using GNSL, matching ambiguity could be reduced.

Coarse-fine vertical scanning based optical profiler for structured surface measurement with large step height

White light interference (WLI) optical profiler had been used widely for structured surface measurement. To achieve high measuring accuracy, piezoelectric ceramic (PZT) was usually used as the vertical scanning unit, which was normally less than 100um and only for small range structured surface measurement. With the development of advanced manufacturing technology, precision structured surfaces with large step height were appearing. To satisfy the measurement requirements of this kind of precision structured surfaces, WLI optical profiler with large range had to be developed. In this paper, an optical profiler was proposed, in which a coarse-fine vertical scanning system was adopted to expand its measurement range to 10mm while its resolution still at nanometer level.

A vertical scanning positioning system with large range and nanometer resolution for optical profiler

Piezoelectric ceramics with a flexible hinge guide was used for fine positioning at nanometer level, while a stepping motor was used for coarse positioning with a resolution at micrometer level, and their combination helped fulfillment of vertical scanning positioning with large range and nanometer resolution. A grating sensor was used for the real-time measurement of scanning displacement for close-loop positioning control. The properties of the flexible hinge guide was analyzed using ANSYS. Experimental results indicated the performance of the system was good. The system had a good application prospect in an optical profiler for surface measurement.

3-D Shape Measurement Based on Optic Interferometric Projection

This paper aimed to use a novel optic interferometric fringe projection to measure the three-dimensional shape of small object with high resolution. In this method, the projecting fringe pattern, which has a sinusoidal density distribution, good contrast and equal spacing, is generated by a spherical wave incident into a triangle-section prism. Project the fringe onto the subject under test, the image of the deformed fringe pattern modulated by object surface is captured by a high-speed CMOS camera and processed by the Fourier Transform technique to extract the phase distribution which is related to height information. An experimental system is set to conduct 3-D shape measurement and the result shows the validity of the proposed method. The projecting system is simple and compact, which helps to realize the integration and miniaturization of the system.

A discounting approach to evidence conflict management

By combining several belief functions from distinct information sources, data fusion aims at obtaining a single Basic Probability Assignment (BPA) function. The classical Dempsters combining rule is the most popular rule of combinations, but it is a poor solution for the management of the evidence conflict at the normalization step. When deal with high conflict information it can even involve counter-intuitive results. A discount method to combine conflicting evidence based on evidence distance is presented; and the discount coefficient of the evidence in the system is also given. Numerical examples showed that the proposed method can provide reasonable results with good convergence efficiency.