System identification for structural engineering has received significant attention in the last thirty years. With the ever increasing capacity of computing technology, system identification has been applied to important structures such as bridges and aircraft. In the case of bridges, the output can easily be measured by accelerometers. Considerable research in system identification on bridges has been done using output-only models. Of course, it is difficult to measure the inputs on an in-service bridge. In this paper, we see how the inputs can be estimated from the output measurements. We then use an input-output model to develop an improved system identification technique for identifying bridges. We show that the proposed method using the estimated inputs yields superior identification in a simulated case (i.e., where everything is controlled). We then use the method on the in-service Walnut Creek Bridge located on the north-bound lanes of U.S. Interstate I-35 between Dallas, TX and Oklahoma City, OK.
Nowadays, 3D Printing Technology, also known as AM - Additive Manufacturing plays an important role in the 4.0 industrial revolution. In 3D printing technologies, FDM (Fused Deposition Modeling) technology is the most popular technology. In general, the quality of AM products and FDM depend on the process parameters. The article addressed the issue of optimizing process parameters to improve the compressive strength of the product. The parameters are considered as the fill pattern, fill density, number of contours, layer thickness and raster angle. The experimental design based on the Taguchi method is employed to identify the optimum process parameters. In addition, ANOVA is also utilized to evaluate the effect of each parameter on the compressive strength of the product.
The 5 DOF coordinate measuring arm is an equipment used to determine the coordinate of points in 3D space at the tangent point of the probe and object. The calculating of the coordinate at the tip of the probe is based on forward kinematic equation of a 5 DOF robot arm, by defining the transpose of the 5 knuckles. Accordingly, we can calculate and measure some geometric elements, such as distance, angle...rebuild surface of object and store data in files. So that, the equipment can be applied in many fieldS: measuring, examining, molding, reverse engineering…
Two most important requirements of Coordinate Measuring Machines (CMM) are the accuracy and the traceability. However, after a long period of use, errors caused by dynamic forces, thermal expansion, loads, etc can decrease the accuracy as well as the traceability. Therefore, CMM is calibrated to minimize these errors as small as possible. First at all, a geometric error model of CMM is proved mathematically. A method of determining 21 parametric errors by using a Hole Plate then is presented. In addition, a back-propagation algorithm is introduced to approximate parametric errors of all points in the CMM working volume. Finally, the proposed calibration method is demonstrated experimentally.
This paper describes algorithms that fit geometric shapes to data sets according to maximum- inscribed (MI) and minimum- circumscribed (MC) fit. We use these fits to build the CMM’s (Coordinate Measuring Machine) software in cases of circle, sphere and cylinder. For each case, we obtain the fit by two methods: first, by (relative easy) least squares fit method and then refine by MI and MC fit method. Although, the later method is substantially more complicated than the former one, Its results are used to make comparision with the the results of least squares method in order to give more options in the CMM software. In the near future we will continue to develop MI and MC fit with an effective algorithm- Simulated Annealing algorithm.
Accurate dimensional inspection and error analysis of free-form surfaces requires accurate registration of the component in hand. Registration of surfaces defined as non-uniform rational B-splines (NURBS) has been realized through an implementation of the iterative closest point method (ICP). The paper presents performance analysis of the ICP registration method using Monte Carlo simulation. A large number of simulations were performed on an example of a precision engineering component, an aero-engine turbine blade, which was judged to possess a useful combination of geometric characteristics such that the results of the analysis had generic significance. Data sets were obtained through CAD (computer aided design)-based inspection. Confidence intervals for estimated transformation parameters, maximum error between a measured point and the nominal surface (which is extremely important for inspection) mean error and several other performance criteria are presented. The influence of shape, number of measured points, measurement noise and some less obvious, but not less important, factors affecting confidence intervals are identified through statistical analysis.
This article refers to the supervision and control information and data remotely over the GSM, GPRS, EDGE. The goal of surveillance is to gather meteorological data, to aggregate assessment.
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