1 Introduction
As an important part of the intelligent building - the development of building automation systems must use a unified specification, high reliability, flexible construction, scalability, easy maintenance, cost-effective way to set up the system, and the air conditioning control system is The main research object. Due to the openness and fully distributed nature of Lonworks fieldbus technology, Lonworks technology can be used as a technical platform for the system to monitor electromechanical devices in real time. This paper establishes an air conditioning control system based on Lonworks.
LonWorks Fieldbus Control Network Technology is a decentralized intelligent control network system. It is a local operation network introduced by Echelon Corporation in the United States in 1991. This technology provides a complete platform for constructing a network system. It provides product developers, system integrators, and end users with Neuron chip microcontrollers, LonTalk protocol, LonWorks transceivers, LonBuilder and NodeBuilder development kits, LonWorks network services architecture LNS, Neuron C programming language, and LonMark interoperability standards. All the techniques needed to develop, construct, install, and maintain a control network. Great convenience for design and production. Therefore, using LonWorks technology to build a building air conditioning control system is not only completely feasible, but also the system has good reliability? Openness and interoperability.
2 Control principle of air conditioning control system based on Lon bus technology
Building automation systems (BAS) are an important part of smart buildings, and air conditioning systems are the most important subsystem in building automation systems. The air conditioning system is controlled, and its control functions are mainly:
(1) Temperature and humidity monitoring. That is to monitor the temperature and humidity of fresh air, return air and exhaust air, and provide basis for the adjustment of temperature and humidity of the system.
(2) Control of the damper. That is, the switching control or analog adjustment of the fresh air valve and the return air valve is performed.
(3) Adjustment of the cold/hot water valve. That is, the opening degree of the valve is adjusted according to the temperature difference between the measured temperature and the set temperature, so that the temperature difference is within the accuracy range.
(4) Control of the humidification valve. That is, when the air humidity is lower than the set lower limit or exceeds the upper limit, the opening and closing of the humidifying valve are separately controlled.
(5) Fan control. That is to achieve the start and stop control of the fan or variable frequency speed control.
(6) Filter differential pressure alarm monitoring, antifreeze switch alarm monitoring, fan fault alarm monitoring.
(7) Condition conversion of air conditioning units (winter, summer, transition season).
(8) Hand/automatic conversion.
3 Structure and hardware design of air conditioning control system based on Lon bus technology
3.1 Overall structural design
Based on the above analysis, the LonBAC-3000 control system is used here.
The LonBAC-3000 system is based on LonWorks technology, with a neuron chip as the core, and is dedicated to the fieldbus system controlled by the air conditioning unit. Its structure is shown in Figure 1.
Figure 1 LonBAC - 3000 basic system diagram
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