Nhiều chương trình CAD hiện nay cho phép tạo ra các mô hình ba chiều để có thể nhìn từ mọi góc độ. Các chương trình CAD mô hình hóa vật thể đặc tiên tiến là một hệ thống thiết kế hiện thực ảo. Những mô hình đặc như vậy có thể được dùng làm cơ sở cho các phân tích phần tử hữu hạn (FEA) và / hoặc tính toán động lực dòng chảy (CFD) của thiết kế. Cho đến ứng dụng gia công với trợ giúp máy tính (CAM), những mô hình này cũng có thể được dùng. | 3 Clock Synchronization of Distributed Real-Time Industrial Data Acquisition Systems Alessandra Flammini and Paolo Ferrari University of Brescia Dept. of Information Engineering Italy 1. Introduction In distributed data acquisition systems for industrial applications the synchronization of the time references of the nodes is essential to guarantee the right real-time behaviour of the system. All the modern distributed automation plants require a clock synchronization mechanism. The use of distributed architectures in industrial applications based on networks has many benefits including high system flexibility and scalability. However this enhancement does not come for free basically a high-performance network communication among the nodes is needed and the data exchange across the network requires more complex management software than centralized systems Felser 2005 . Moreover a key point in all distributed data acquisition systems is the synchronization of the time reference among the nodes Eidson Lee 2003 . A typical automation plant is composed by several distributed nodes controllers sensors and actuators that need to sample and control the system in a time coordinated fashion. Considering the real-time applications for data-acquisition the clock synchronization of the time reference across the network is essential in order to support Data fusion of the measures obtained using distributed data acquisition system and sensors Proft 2007 . Distribute signal processing which takes the time into account. Coordination of the actions across a distributed set of actuators if a control action has to be taken. Optimization of the transmission bandwidth in the network thanks to channel medium access control such as TDMA Time Division Multiple Access for both wired and wireless systems Ueda Yakoh 2004 . The scientific community has proposed several types of synchronization algorithms some of them are dedicated to wired networks with different kind of complexity and .
