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

Heat, Ventilation and Damper Control TrendsPC use has steadily expanded in spite of persistent worries aboutnondeterministic behavior.Just a few years ago, PCs were used as motion programmers andas OIs, while the actual motion control was done by a dedicated unitthat drove a separate amplifier. Then, motion control cards wereplugged into the PC’s backplane. The next step is to let the PC do themotion controller task in software, using its own real-time operatingsystem.PCs will take over an increasing part of the data handling andcommunications function, helping to tie the motion control function intothe entire system or network. Dedicated, proprietary boxes will be in thepast as open controls become the future. As PC-based controls dominate,there will be a continued trend towards more general-purpose controllers.As these general-purpose motion controls start to dominate, costswill be driven downward through better manufacturing techniques,including reducing the controller to the chip level.PC-based control software has achieved development time savingsdue to a single programming environment, single database, and fullintegration with logic and HMI (human-machine interface) functions.Continued advancements in mainstream PC technology includefaster processors, better operating systems, advanced client/server computingarchitecture, new communications technologies and computerbasedtools for test, measurement and industrial automation.The PC allows measurements to be easily sequenced, processed,displayed, and stored. Seamless integration of motion is fundamental tothe success of automated systems. The PC is the viable platform forthese integrated systems.There are PC-based control system that include PLC functions tofieldbus I/O, motion control via SERCOS, and communications via serialports and Ethernet. In the future this could all be done more simplywith plug-in Java Beans for motion control or for the interface betweenmotion control and the HVAC system.Motion control will become a software function running on a realtimeoperating system in a PC, at first under Windows NT, and laterperhaps under CE. The control program will be a combination of softmotionand soft-logic technology. Logic programming will be standardizedby IEC-1131-3 while motion programming may continue to be vendorspecific until a similar standard is developed for motion controllers.The PC will then be enabled to take a greater role in motion control.©2001 by The Fairmont Press, Inc. All rights reserved.