Beitrag zur voxelbasierten Simulation des fünfachsigen NC-Fräsens

Die Simulationstechnik wird als Hilfsmittel zur Beherrschung der drei- und fünfachsigen NC-Fräsbearbeitung eingesetzt. Gewöhnlich wird die Aktualisierung des simulierten Werkstücks entweder im Bildraum des Werkstücks oder geometrisch im Objektraum durchgeführt. Die vollständige Aktualisierung des simulierten Werkstücks fordert jedoch nur eine geometrische Lösung. Im vorliegenden Forschungsbericht wird der Ansatz der voxelbasierten fünfachsigen NC-Simulation entwickelt. Die Grundlage für den Aufbau des Simulationssystems ist der am IPK Berlin entwickelte 3D-Kernmodellierer des Virtual Clay Modelling Systems. Dieser ermöglicht die Modellierung und die Aktualisierung von komplizierten Werkstücken und Zerspanungsvolumen in der drei- und fünfachsigen NC-Simulation auf Rechenanlagen. Das simulierte Werkstück wird rechnerintern diskret mit einem Voxelmodell dargestellt. Die dadurch eingeführten NC-Simulationsfehler werden unter Berücksichtigung des eingesetzten Fräsers kontrolliert. Eine voxelbasierte Methode zur Gestaltung von Zerspanungsvolumen der diversen Werkzeuge wie zylindrische Fräser, Torus-, zylindrische Gesenk-, Kugelkopf-, Fass-, Kegel- und kegelige Gesenkfräser wurde entwickelt. Der Vorteil dieser Methode liegt darin, dass aufgrund der diskreten Datenstruktur des Voxelmodells und der damit ermöglichten Abbildung von beliebigen Formen keinerlei Einschränkungen zur Modellierung der Zerspanungsvolumen der diversen Fräsertypen gegeben sind. Die Materialverletzungen und verbliebenen Restmaterialien auf dem simulierten Werkstück können im 3D-Raum zur Bewertung der Qualität der NC-Programme ermittelt werden. Eine effektive Optimierung der NC-Programme in der Fertigungsvorbereitung kann durchgeführt werden. Zur Beschleunigung der Werkstückaktualisierung wurden ausgehend von den Eigenschaften des Voxelmodells die entsprechenden Maßnahmen getroffen. Mit der vorgestellten Methode wird ein wichtiger Beitrag zur drei- und fünfachsigen Simulation des NC-Fräsens geleistet. Damit können die NC-Programme für die drei- und fünfachsige NC-Fräsbearbeitung verifiziert, optimiert und die Prozessqualität vorab sichergestellt werden

The Simulation of the Brush Stroke Based on Force Feedback Technology

A novel simulation method of the brush stroke is proposed by applying force feedback technology to the virtual painting process. The relationship between force and the brush deformation is analyzed, and the spring-mass model is applied to construct the brush model, which can realistically simulate the brush morphological changes according to the force exerted on it. According to the deformation of the brush model at a sampling point, the brush footprint between the brush and the paper is calculated in real time. Then, the brush stroke is obtained by superimposing brush footprints along sampling points, and the dynamic painting of the brush stroke is implemented. The proposed method has been successfully applied to the virtual painting system based on the force feedback technology. In this system, users can implement the painting in real time with a Phantom Desktop haptic device, which can effectively enhance reality to users

A Novel Virtual 3D Brush Model Based on Variable Stiffness and Haptic Feedback

A novel variable stiffness 3D virtual brush model and haptic decoration technique suitable for the surface of the three-dimensional objects for the automobile industry are introduced based on real-time haptic feedback mechanism using a 6 DOFs input device, and the haptic behavior of an expressive virtual 3D brush with variable stiffness is studied in detail for the first time. First, the intrinsic mechanism between the deformation of real hair brush and the applied external forces (such as the bending moment) is analyzed and studied in detail by introducing a bending spring to express the basic mechanical behavior for the 3D hair brush. Based on this brush model, many important painting features can be simulated, such as the softer brush tip, brush flattening, and bristle spreading. And a useful algorithm (named the weighted-average distance) for dealing with collision checking among the two objects (3D clay and the 3D brush) is presented. As long as the brush head is close to the 3D object, within a tolerance range, the computational tactile sensation force will be emerged, and the interactive painting process is implemented actually on the outer surface of the virtual object. We then calculate the related bounding ball for deformed 3D brush using a fast ball-expanding search algorithm to determine the virtual projection plane. Based on the real-time deformation about the virtual brush head at a sampling point, the 2D painting footprints, which is produced between the brush head and virtual projection painting plane, is calculated and rendered. Next, the 3D painting footprint could be easily produced via mapping the 2D painting footprints onto the surface of the 3D model in real time. Finally, the 3D painting strokes are formed via controlling the exerted force and overlapping the virtual 3D painting footprints with different shape, size, and following the moving direction of the 3D brush. Experiment result shows that the adopted method can effectively enhance reality to users, with high performance

Bivariate Correlation Analysis of the Chemometric Profiles of Chinese Wild Salvia miltiorrhiza Based on UPLC-Qqq-MS and Antioxidant Activities

To better understand the mechanisms underlying the pharmacological actions of Salvia miltiorrhiza, correlation between the chemical profiles and in vitro antioxidant activities in 50 batches of wild S. miltiorrhiza samples was analyzed. Our ultra-performance liquid chromatography–tandem mass spectrometry analysis detected twelve phenolic acids and five tanshinones and obtained various chemical profiles from different origins. In a principal component analysis (PCA) and cluster analysis, the tanshinones cryptotanshinone, tanshinone IIA and dihydrotanshinone I exhibited higher weights in PC1, whereas the phenolic acids danshensu, salvianolic acids A and B and lithospermic acid were highly loaded in PC2. All components could be optimized as markers of different locations and might be suitable for S. miltiorrhiza quality analyses. Additionally, the DPPH and ABTS assays used to comprehensively evaluate antioxidant activities indicated large variations, with mean DPPH and ABTS scavenging potencies of 32.24 and 23.39 μg/mL, respectively, among S. miltiorrhiza extract solutions. Notably, samples that exceeded the mean IC50 values had higher phenolic acid contents. A correlation analysis indicated a strong correlation between the antioxidant activities and phenolic acid contents. Caffeic acid, danshensu, rosmarinic acid, lithospermic acid and salvianolic acid B were major contributors to antioxidant activity. In conclusion, phenolic compounds were the predominant antioxidant components in the investigated plant species. These plants may be sources of potent natural antioxidants and beneficial chemopreventive agents