Showing papers by "Chia-Hsiang Menq published in 1999"

A linear/angular interferometer capable of measuring large angular motion

Abstract: A novel linear and angular interferometric heterodyne system, capable of measuring large angular motion, is proposed. The interferometric system has a high linear-displacement resolution of 1.24 nm while the angular-displacement resolution can reach 0.0025 arcsec. By combining the advantages of the interferometer with a retroreflector and the interferometer with a plane-mirror reflector, the proposed interferometric measurement system allows a desirable transverse motion and rotational motion along any of the three orthogonal directions. Using a retroreflector with a diameter of 38.1 mm, the translational range in the transverse directions is no less than 20 mm × 10 mm while the angular range along any axis is no less than 10°. The angular readings can be used to compensate the linear outputs in real time when the Abbe error occurs. This ability has been demonstrated by the experiments.

Prediction of Periodic Response of Blades Having 3D Nonlinear Shroud Constraints

Abstract: In this paper, a 3D shroud contact model is employed to predict the periodic response of blades having 3D nonlinear shroud constraint. When subjected to periodic excitation, the resulting relative motion at the shroud contact is assumed to be periodic in three-dimensional space. Based on the 3D shroud contact model, analytical criteria are used to determine the transitions between stick, slip, and separation of the contact interface and are used to simulate hysteresis loops of the induced constrained force, when experiencing periodic relative motion. The constrained force can be considered as a feedback force that influences the response of the shrouded blade. By using the Multi-Harmonic Balance Method along with Fast Fourier Transform, the constrained force can be approximated by a series of harmonic functions so as to predict the periodic response of a shrouded blade. This approach results in a set of nonlinear algebraic equations, which can be solved iteratively to yield the periodic response of blades having 3D nonlinear shroud constraint. In order to validate the proposed approach, the predicted results are compared with those of the direct time integration method. The resonant frequency shift, the damping effect, and the jump phenomenon due to nonlinear shroud constraint are examined. The implications of the developed solution procedure to the design of shroud contact are also discussed.Copyright © 1999 by ASME

Multiple-sensor integration for rapid and high-precision coordinate metrology

Abstract: This paper presents an integrated framework that supports multiple sensor integration for rapid and high precision coordinate metrology. Rapid acquisition of high precision coordinate data from parts having complex geometry has many applications. Typical examples include part localization and automatic calibration in inspection and agile machining, coordinate metrology in dimensional control, and reverse engineering in rapid product design and realization. In this paper, information aggregation technology that facilitates rapid acquisition of high precision coordinate data is developed and demonstrated using a multi sensor integrated coordinate measuring system. The multi-sensor coordinate measuring system consists of a high precision coordinate measuring machine (CMM), a motorized probe, and an active vision system. The active vision system along with intelligent feature recognition algorithms provides the global information of the unknown object, including location and orientation, surface geometry, and feature topology. The obtained information is subsequently used to plan the most informative view for the next measurement, to guide the mechanical probe for high speed coordinate data acquisition, and to strategically control the coordinate measuring machine for high precision/rapid sampling of critical surface areas. By integrating the developed technology with the state of the art equipment, a highly automated, high speed, high precision, 3D coordinate acquisition system is developed. It has potential applications in a whole spectrum of manufacturing problems with a major impact on metrology, inspection, and reverse engineering.

Uncertainty analysis and variation reduction of three dimensional coordinate metrology. Part 1: geometric error decomposition

Abstract: In this paper our study focuses on the uncertainty analysis and variation reduction of coordinate system estimation using discrete measurement data and is associated with the applications that deal with parts produced by end-milling processes and having complex geometry. This paper consists of three parts. Since the uncertainty of the estimated coordinate transformation arises from the geometric errors on a part surface, Part 1 is devoted to the study of surface geometric errors. In this study, according to the characteristics of end-milling processes the sampled geometric error is divided into two components, and a decomposition procedure is developed for geometric error decomposition. The results of surface geometric error decomposition will be used in Part 2 for uncertainty analysis and in Part 3 for variation reduction.

Uncertainty analysis and variation reduction of three-dimensional coordinate metrology. Part 2: uncertainty analysis

Abstract: In this part of the paper, the uncertainty analysis of coordinate estimation for the case in which the sampled geometric errors are dominated by the random component is investigated. In practice, the uncertainty analysis of coordinate estimation using high-precision datum surfaces often falls into this type. In this paper, a sensitivity matrix, which serves as the theoretical basis of the uncertainty analysis, is presented to establish a linearized relationship between the variations of the coordinate estimation and the geometric errors of the part surface at the measurement points. Based on the sensitivity matrix, quantitative measures are derived for the prediction of coordinate variation. Computer simulation and experiments are conducted to verify the theoretical predictions when the surface geometric errors are small and dominated by the random component.

Prediction of Resonant Response of Shrouded Blades With Three-Dimensional Shroud Constraint

Abstract: In this paper, the three-dimensional shroud contact kinematics of a shrouded blade system is studied. The assumed blade motion has three components, namely axial, tangential, and radial components, which result in a three dimensional relative motion across the shroud interface. The resulting relative motion can be decomposed into two components. The first one is on the contact plane and can induce stick-slip friction. The other component is perpendicular to the contact plane and can cause variation of the contact normal load and, in extreme circumstances, separation of the two contacting surfaces. In order to estimate the equivalent stiffness and damping of the shroud contact an approach is proposed. In this approach, the in-plane slip motion is assumed to be elliptical and is decomposed into two linear motions along the principal major and minor axes of the ellipse. A variable normal load friction force model (Yang and Menq, 1966) is then applied separately to each individual linear motion, and the equivalent stiffness and damping of the shroud contact can be approximately estimated. With the estimated stiffness and damping, the developed shroud contact model is applied to the prediction of the resonant response of a shrouded blade system. The effects of twomore » different shroud constraint conditions, namely two-dimensional constraint and three-dimensional constraint, on the resonant response of a shrouded blade system are compared and the results are discussed.« less

Uncertainty analysis and variation reduction of three dimensional coordinate metrology. Part 3: variation reduction

Abstract: In this paper, the study focuses on the coordinate variations for the case in which the deterministic error component of the sampled geometric errors is no longer negligible compared to the random error component. Two different approaches are proposed for the estimation of coordinate transformation. In the one-step approach, the best-fit method is applied to directly fit the measurement data to the nominal surface. In the two-step approach, a deterministic surface is first constructed from the measurement data and the fitted deterministic surface is then best-fitted with the nominal surface to estimate the coordinate transformation. The computation needed in the two-step coordinate estimation approach is more expensive than that required by the one-step approach. However, by estimating the deterministic error component of the surface geometric error, the two-step approach can effectively reduce the influence of the deterministic error component on the result of coordinate estimation. Therefore, with the same measurement data, the two-step approach gives a much more accurate coordinate estimation result than the one-step approach. In addition, the variation range of the obtained coordinate transformation parameters is much reduced.