| HC Network Security Building Automation | | | | through the analog input channels (AI) and digital |
| System, also known as building automation | | | | input channels (DI) real-time data collection, and |
| system (BuildingAutomationSystem short BAS), is | | | | then calculated according to certain rules, and |
| Intelligent Building Indispensable part of its mission | | | | finally the control signals, and through the analog |
| is the building's energy use, environmental, traffic | | | | output channels (AO) and the switch output |
| and Security Facilities monitoring, control, etc., to | | | | channel (DO ) direct control of the production |
| provide a safe, reliable, saves energy, but also a | | | | process. So DDC system is a closed-loop control |
| comfortable and pleasant working or living | | | | system is a computer in the industrial production |
| environment. | | | | process, the most common way of an application. |
| 2 building automation system components and | | | | DDC system control computer to undertake the |
| basic functions | | | | task, which required real-time, high reliability and |
| Building automation system typically includes | | | | adaptability. |
| HVAC Drainage, power supply, lighting, elevators, | | | | 3.1.1 Composition of direct digital control system |
| fire safety and prevention and other subsystems. | | | | Direct digital control system consists of the |
| According to China's industries Standard , BAS can | | | | process input channel, process control computer, |
| be divided into device management and control | | | | the process of output channels of three parts. |
| subsystem operation and fire prevention and | | | | Process input channels from the analog input and |
| safety subsystems, as shown. Under normal | | | | digital input of two parts. Analog input channels |
| circumstances, the two subsystems together into | | | | from the transmitter, the sampling switch, |
| the BAS should be considered, such as fire and | | | | amplifier, A / D converter and interface circuit. |
| safety precautions will be set up independently | | | | One is the role of the transmitter signal will be |
| subsystem should also be established with the | | | | converted into the standard non-power electrical |
| BAS control center Communicate Contact for | | | | signals can be temperature, pressure, flow |
| disaster occurs, the right to operate in accordance | | | | transformed into 0-10mA or 4-20mA DC signal, it |
| with the agreed transfer to achieve, for the | | | | is through A / D converter to achieve. ? Digital |
| integration of coordinated control. | | | | input channels from the switch contacts, |
| Building automation system's basic functions can | | | | photoelectric coupler and interface circuit, |
| be summarized as follows: | | | | reflecting the production process on / off state |
| (1) automatically Monitoring And control of various | | | | of the contact signal, through the optocoupler and |
| electrical and mechanical equipment, the stop, | | | | the interface circuit transformation into a digital |
| display or print the current operating state. | | | | signal sent to the computer. |
| (2) automatically Detect , Display, print a variety | | | | Direct commitment to the process control |
| of electrical and mechanical equipment operating | | | | computer operations and control tasks, first of all |
| parameters and changes in trends or historical | | | | input channels through the process of collecting |
| data. | | | | the parameters of the object and signals, then |
| (3) according to external conditions, environmental | | | | the scheduled control law (such as PID) for |
| factors, the change automatically adjust the load | | | | operation, and then send control signals to the |
| of equipment, so that is always running in top | | | | controlled object, and through the output channels |
| condition. | | | | such as direct control valve actuator. |
| (4) monitoring and timely processing of all accident | | | | Process output channel from the analog output |
| emergencies. | | | | and digital output of two parts. The former |
| (5) to achieve a variety of electrical and | | | | control of the computer output of digital signals |
| mechanical equipment on building a unified | | | | into analog voltage or current signals, through the |
| management, coordination and control. | | | | amplifier to drive control valve actuators to |
| (6) Energy Management: Water, electricity, gas, | | | | achieve control of the production process. This |
| etc. metering and charging, developing energy | | | | part of the interface circuit, D / A converter, |
| management automation. | | | | amplifier and actuator component. The latter |
| (7) Equipment Management: including device files, | | | | switches the computer output signal, by the |
| equipment operation and equipment maintenance | | | | amplifier to drive solenoid valve and relay |
| management reports. | | | | actuator, which consists of interfaces electrical, |
| 3 the principle of building automation control | | | | optical coupler, amplifier and actuator component. |
| system | | | | 3.1.2 direct digital control system the basic |
| Floor control system used in modern control | | | | algorithm |
| theory is based on Distributed Computer Control | | | | In accordance with the deviation ratio (P), integral |
| System, also known as distributed control system | | | | (I) and differential (D) control, a continuous |
| (Distributedcontrolsystems referred to as DCS). It | | | | system technology is mature, the most widely |
| is characterized by a "centralized management | | | | used as a basic rule, the discrete PID control law |
| decentralized control," that is charged with | | | | and on computer , can easily use the mature |
| distribution of equipment in the field office of the | | | | technology has been accumulated, and can be |
| micro-computer control (DDC) to complete device | | | | charged with the mathematical model or |
| charged with the task of real-time detection and | | | | parameter is not very clear circumstances, and |
| control, centralized control of computer to | | | | after online tuning to achieve satisfactory results. |
| overcome the risks of high lack of centralized | | | | Therefore, the law regulating discrete analog digital |
| control and conventional single instrument | | | | PID algorithm, computer control of industrial |
| limitations. Installed at the central control room of | | | | processes have been widely adopted system, a |
| the central management computer has a CRT | | | | DDC system, the basic algorithm. |
| display, print output, rich software management | | | | Digital PID control algorithm, analog PID controller |
| and strong digital communications capabilities, able | | | | formula for the ideal |
| to complete the concentration operation, display, | | | | Type of e (t)?? Deviation (set value and the |
| alarm, control and optimization tasks such as | | | | difference between the actual output value) |
| printing, to avoid the spread of conventional | | | | U (t)?? Control volume Kp?? Scaling factor Ti an |
| instrumentation control After the man-machine | | | | integral time constant Td?? Differential time |
| contact difficulties, the shortcomings can not be | | | | constant Written in the form of transfer function |
| unified management to ensure the equipment | | | | In order to implement on a computer, you must |
| running in top form. | | | | be a continuous form of differential equations into |
| Here are distributed control systems with several | | | | a discrete form of differential equations. Set for |
| concepts. | | | | the sampling period (compared with the system |
| 3.l direct digital control system (DDC) | | | | time constant, T is small enough), k is sampling |
| Direct digital control system (DirectDigitalControl | | | | number (k = 0,1,2, ... ... |
| referred to as DDC) shown in Figure 2. Computer | | | | |