Brief analysis of advantages of ba-protocol-bacnet Protocol

Bacnet-building Automation and control network for short, for the building automation network and communication protocols developed. An open building automation communication standard developed by the American Association of HVAC Engineers. December 1995 was approved as the United States national standards, and formally named Ansi/ashrae 135-1995 Standard. January 2003 becomes the official standard iso16484-5 of the ISO. BACnet with its openness, ease of expansion, flexibility of the characteristics of the majority of building automation manufacturers and users recognized. At present, BACnet has become the absolute mainstream in the building automation market. This paper briefly analyzes the characteristics of BACnet from the basic technology used in BACnet and the BACnet network system.

BACnet is a protocol designed specifically for building automation, using object-oriented technology to represent building automation equipment. The object-oriented method is used to represent the basic functional units of building automation, such as analog quantity, digital output, time schedule and so on. Any building automation equipment can be decomposed into such basic functional units. These basic functional units are represented by objects in BACnet, making these basic functional units reusable and global in nature.

And the other commonly used in the building of a protocol LonWorks compared to BACnet in the technical level has a greater leading edge, LonWorks function block is basically focused on data sharing, monitoring, operation, alarm basic functions, but BACnet also support the timetable, trends and other advanced features, more suitable for building automation, Table one is a few simple comparisons.

Function	BACnet	LONMARK
Data sharing	Yes	Yes
Monitoring, operation and alerting	Yes	Yes
Schedule	Yes	No
Online Binding/Unbinding	Yes	No
Trending/historical data	Yes	No
Backup/Restore	Yes	No
Remote Management	Yes	No

Table I.

Using Instance to identify the same object in BACnet means that the basic functional unit represented by the same object can be reused in the BACnet Building automation system and can be addressed. The Instance range of each object is 0-4194303, and the range of 0 to 4 million allows BACnet to form an oversized system. BACnet uses attributes to describe the state of an object. The more properties an object has, the more performance the object displays. The properties of an object are recognized and accessed on the network by each other.

BACnet defines a number of services to operate on the object's attribute values, rather than directly manipulating the object, so that the communication and control can be separated, the BACnet protocol only specifies the behavior of the communication, not the specific building control behavior, there is no definition of the control of the implementation of the way, Allow individual vendors to retain their uniqueness, without stifling the creativity of individual manufacturers. For example, within the Siemens PXC series BACnet Controller

Independent model-Free adaptive Control algorithm for Siemens. Model-Free adaptive control can automatically correct parameters to compensate machine

System/load/seasonal variation, it provides more efficient, better robustness, faster and more stable control than conventional PID control. Compared with the PID control, the adaptive control has excellent performance in the dynamic nonlinear system's response time, maintaining steady state and reducing errors.

The use of object-oriented technology to express the building method, so that the basic building Automation function unit is not only reusable, global, easy to expand, while separating the building automation equipment communication and control, so that the control products of each manufacturer can still maintain their own characteristics.

In view of the function of building automation, BACnet in the network system, using the open System Interconnect 7 Layer Reference Model OSI, and optimized. Because for the building automation system, the content of the transmission on the network is relatively single, fixed. And in general, the transmission of information within the LAN, even if it is remote communication, can also borrow public telecommunications network to achieve. This makes the presentation layer, the session layer, and the transport layer in the OSI model unnecessary in the BACnet system. At the same time, the BACnet system supports a variety of networking methods in the physical layer and data link layer. BACnet can use different LAN technology, there are suitable for high-speed high-cost network technology, but also suitable for low-cost network technology, theoretically BACnet can be transmitted to any BACnet service data unit of the media can be used as a BACnet transfer tool. So that the BACnet system can adapt to the future network technology and can be backwards compatible with the installed system. Through the support of different LAN technology, the local BACnet network in a project can be composed of different LAN technologies, which can provide the best cost-effective service to the users according to the specific needs of the equipment.

The BACnet system also has a good support for IP networks. The BACnet can be seamlessly extended to the BACnet network. Receive and send BACnet messages with IP frames, because the TCP protocol does not allow one-to-many broadcasts, and many of the messages in the building automation system are implemented by broadcast and multicast, so the IP protocol uses the UDP protocol instead of the TCP protocol. BACnet when a reliable message needs to be transmitted, a separate BACnet is used (which confirms

Service without using the TCP protocol.

BACNET/IP is the fastest and best-performing building Automation network communication protocol in the modern times. Matching fast and high performance to the DDC controller to handle complex control tasks, such as VAV air conditioning system, cold cluster control and other high-demand control, there are great benefits, while BACNET/IP from the protocol layer directly support control information, such as trends, scheduling, alarm, file transfer and database management, etc. Fully applicable to the highest requirements of the smart buildings at this stage, from a market perspective, also proved that the BACnet agreement will undoubtedly become the next generation of building control system has a dominant status of the agreement

As a special agreement for building automation design, BACnet from all aspects of the building automation needs, the use of pioneering technology to enable different manufacturers of equipment can be interconnected, can say that BACnet is specifically for building automation and customized standards, but also is the direction of building automation development.

Brief analysis of advantages of ba-protocol-bacnet Protocol