Posture adjustment of workpiece based on stepwise matching by self-adaptive differential evolution algorithm

The workpiece contour errors from previous process affect current and subsequent process. In order to improve the uniformity of workpiece allowance distribution, a stepwise workpiece matching adjustment method with contact inspection is developed. This method includes two stepwise registration processes. At first, some pairs of measured points on the theoretical and actual surfaces are selected to build the corresponding local coordinate systems, and then the rough matching matrixes are obtained by the coordinate systems alignment. During the fine matching process, the objective function based on the least square method is established by the measured point sets adjusted through the rough matching. The fine matching matrixes can be obtained by self-adaptive differential evolution algorithm. The posture adjustment can be realized by transforming coordinate systems of 5 axis machine tool, of which adjusted values can be calculated by the matching matrixes and the machine tool topology. At last, some experiments were presented to demonstrate the performance of the method.</p

YERSEL LAZER TARAYICI NOKTA BULUTLARININ BİRLEŞTİRİLMESİ VE JEODEZİK KOORDİNAT SİSTEMİNE DÖNÜŞTÜRÜLMESİ: LİTERATÜR ARAŞTIRMASI

YERSEL LAZER TARAYICI NOKTA BULUTLARININ BİRLEŞTİRİLMESİ VE JEODEZİK KOORDİNAT SİSTEMİNE DÖNÜŞTÜRÜLMESİ: LİTERATÜR ARAŞTIRMASIÖzetYersel lazer tarayıcılarla üç boyutlu (3B) modelleme çalışmalarında, nokta bulutlarının birleştirilmesi en önemli işlem adımlarından birisidir. Bu amaçla bugüne kadar pek çok yöntem geliştirilmiştir, ancak lazer tarayıcı nokta bulutlarının birleştirilmesi hala önemli bir araştırma konusudur. Diğer yandan nokta bulutlarının otomatik birleştirilmesi de ciddi bir araştırma konusudur ve her türlü veri seti için uygulanabilecek standart bir yöntem bulunmamaktadır. Uygulanan yöntemler; otomasyon, doğruluk, hesaplama süresi, nokta yoğunluğu ve ölçü hatalarına duyarlık bakımından farklılıklar göstermektedir. Ayrıca lazer tarama verilerinin başka konumsal verilerle entegrasyonu için jeodezik koordinat sistemi gibi ortak bir koordinat sistemine dönüştürülmesi gerekir. Ölçme tekniği ve lazer tarayıcı aletinin konfigürasyonuna bağlı olarak jeodezik koordinatlandırma yöntemleri değişiklik göstermektedir. Bu çalışmada lazer tarayıcı nokta bulutlarının birleştirilmesinde kullanılan yöntemler sınıflandırılmış ve belirli özellikleri vurgulanmıştır. Böylece nokta bulutlarının birleştirilmesi ve jeodezik koordinat sistemine dönüştürülmesi konusunda uygulayıcı ve araştırmacılara yol gösterici olunması amaçlanmıştır.Anahtar Kelimeler: Yersel lazer tarama, Nokta bulutu, Birleştirme, Üç boyutlu dönüşüm, LIDAR, Jeodezik koordinatlandırma.REGISTRATION AND GEOREFERENCING METHODS FOR POINT CLOUDS OF TERRESTRIAL LASER SCANNER: A REVIEWAbstractPoint cloud registration is bottle neck on three-dimensional (3B) modelling by using terrestrial laser scanner. Many methods have been developed for the registration of point clouds so far. Neverthless, it is still important research topic. Automatic registration of point clouds is also one of the important research topic on three-dimensional modelling. There are no standart methods for applying all type of data sets. The registration methods have different specicifications in respect to automation, accuracy, computation time, point density and susceptiblity from irregular points. On the other hand, the point clouds have to be registered into extensive coordinate system like this geodetic system for the integration with the other spatial data. Georeferencing methods of point clouds change according to measurement methods and configuration of laser scanner instrument. In this study, point cloud registration methods have been classified and emphasized their main properties. Thus, it had to be given informataion for the applicants and researchers about point cloud registration and georeferencing.Keywords: Terrestrial laser scanning, Point cloud, Alignment, Three-dimensional registration, LIDAR, Georeferencing

NUMERICAL ESTIMATION OF MECHANICAL PROPERTIES OF HUMAN TRABECULAR BONE TISSUE: A NEW METHOD BASED ON DIGITAL IMAGE CORRELATION.

The estimation of tissue level mechanical properties of trabecular bone is still a hard task. A widely used technique is based on the combination of mathematical models, obtained through µCT images, with displacements measurements registered during uni-axial compression tests. One of the main limitation of this approach is linked to the method used to measure the displacements which considers punctual acquisition for an inhomogeneous material. Moreover, the measuring instruments require the contact with the sample surface exposed to the mechanical tests, creating local artefacts which may produce significant differences between the numerical model and physical system. Recently, techniques based on the image correlation allowed the measurement of the displacements field on a surface portion during the experimental test. This thesis develops a method to integrate the DIC measurements with the numerical models obtained through micro-CT images, in order to estimate the mechanical properties of trabecular bone tissue. An accurate registration between experimental measures and numerical model is developed and qualified through sensitivity studies on the characterizing parameters. The comparison of the displacements measured values with the foretold ones, allows to quantify the coherence between numerical model and physical model. Finally, the acquired experimental information are used to estimate the mechanical properties at the tissue level, leading to values coherent with the estimations realized with the punctual methods, assumed as reference

Pre-registration of arbitrarily oriented 3D surfaces using a genetic algorithm

This paper reports on a successful application of genetic optimisation in 3D data registration. We consider the problem of Euclidean alignment of two arbitrarily oriented, partially overlapping surfaces represented by measured point sets contaminated by noise and outliers. Recently, we have proposed the Trimmed Iterative Closest Point algorithm (TrICP) [1] which is fast, applicable to overlaps under 50% and robust to erroneous and incomplete measurements. However, like other iterative methods, TrICP only works with roughly pre-registered surfaces. In this study, we propose a genetic algorithm for pre-alignment of arbitrarily oriented surfaces. Precision and robustness of TrICP are combined with generality of genetic algorithms. This results in a precise and fully automatic 3D data alignment system that needs no manual pre-registration

Women in Science 2012

The summer of 2012 saw the number of students seeking summer research experiences with a faculty mentor reaching record levels. In total, 179 students participated in the Summer Undergraduate Research Fellows (SURF) program, involving 59 faculty mentor-advisors, representing all of the Clark Science Center’s fourteen departments and programs.https://scholarworks.smith.edu/clark_womeninscience/1011/thumbnail.jp