HVAC Control in the New Millennium.pdf - HVAC.Amickracing

PC-based Control, Software and Bus Trendsincompatible properties in the same operating system. One is hard realtimeservice with its predictable, fast, low latency, simple scheduler. Theother is the services of GUI, TCP/IP and web-servers.Linux is a low-cost OS with a high-performance microkernel architecture.Linux is the ultimate example of open architecture, with hundredsof thousands of end-user contributions.Object TechnologyThe trend towards open source software continues with objecttechnologies and Internet protocols making it possible. There were nostandards available for object technology back in the 1980s, so the realtimeObject Manager was developed. This type of object-based softwareand communications infrastructure provides a high degree of hardwareand operating system independence.Today, there are many industry and defacto object standards suchas Java, CORBA, OPC, Active X and DNA. Each has its place within thecomplete sensor-to-database automation solution. There has been muchsuccess in using Foxboro’s Object Manager with these industry anddefacto object standards to create object-enabled environments.Many of these applications can run on a number of operating systemsincluding Windows NT, SUN OS, Solaris, VRTX, and Venix. StandardTCP/IP networks, OpenVMS, HP-UX and AIX are also supported.Several object-oriented technologies are playing important roles incontrol software. These are OPC, ActiveX and Java. The latter two arefinding their roles primarily in networks and the Internet. CORBA andORB are also object technologies, but these are found primarily on UNIXsystems and typically work at enterprise levels. They have not seenmajor use in industrial data communications.OLE (Object Linking and Embedding) was Microsoft’s originalobject-based communications technology within Windows. OLE allowsyou to assign tasks to objects and create integrated applications that canshare data.OLE was replaced by the newer OPC (OLE for process control). Inprocess control, OLE/OPC opened up communications between devicesand software applications in the Windows environment. OPC becamethe standard technique for exchanging data between clients and servers.OPC toolkits from companies such as PC Soft extended the technology©2001 by The Fairmont Press, Inc. All rights reserved.