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

PC-based Control, Software and Bus TrendsOPC has been speed. In some control software OPC could be too slowto use.OPC may become the generic data exchange mechanism for industrialautomation. For zone automation, it is not the platform that is mostimportant, it’s communication. Where performance is needed in the PCbasedcontrol, DCX enhancements can be used to supplement OPC.DCXDCX is a newer architecture that may be adopted as a standardreal-time communications specification. OPC and Microsoft’s COM(component object model) can provide enterprise support for data communications,but do not provide real-time deterministic response.DCX uses a publish-and-subscribe based model to provide drivershells for common devices, hard real-time development tools, standardconfigurators and OPC. DCX offers CE and NT portability, provides OSisolation, offers plug-and-play with applications and drivers from differentvendors and supports OPC connectivity (Figure 5-6).Component SoftwareComponent software is a major concept for new application development.The two basic models are Microsoft’s component object model(COM) and the Object Management Group’s common object requestbroker architecture (CORBA). The Object Management Group is a consortiumof major software and hardware vendors.COM is used to build systems based on the Microsoft Windowsenvironment. CORBA is used to build systems using more diverse operatingenvironments such as IBM’s MVS, CICS, Unix versions or WindowsNT.Microsoft has been developing the technologies for building componentsin the versions of OLE, COM and ActiveX. These standardsmust be implemented in either Microsoft Foundation Class or ActiveTemplate Libraries.Component developers have focused on developing user interfacecomponents. These include component libraries of charts and panels.Developers of industrial automation software have extended that con-©2001 by The Fairmont Press, Inc. All rights reserved.