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1、精选优质文档-倾情为你奉上外文文献原稿和译文原稿Multiple single-chip microcomputer approach tofire detection and monitoring systemA.J. AI-Khalili, MSc, PhDD. AI-Khalili, MSc, PhDM.S. Khassem, MScIndexing term : Hazards, Design, Plant condition monitoringAbstract: A complete system for fire detection and alarm monitoring ha
2、s been proposed for complex plants. The system uses multiple single chip architecture attached to a party line. The control algorithm is based on a two-level hierarchy of decision making, thus the complexity is distributed. A complete circuit diagram is given for the local and the central station wi
3、th requirements for the software structure. The design is kept in general form such that it can be adapted to a multitude of plant configurations. It is particularly shown how new developments in technology, especially CMOS single chip devices, are incorporated in the system design to reduce the com
4、plexity of the overall hardware, e.g. by decomposing the system such that lower levels of hierarchy are able to have some autonomy in decision making, and thus a more complex decision is solved in a simple distributed method.1 IntroductionRegulatory requirements for most high risk plants and buildin
5、gs mandate the installation of fire detection and warning systems for all sensitive areas of the plant or the building. Most fire codes state the requirement for monitoring and control specifically related to a type of a plant or building such as chemical plants, petroleum, nuclear plants, residenti
6、al high-rises etc. A general conclusion of these codes can be specified as the following requirements :(a) The source of all detector signals should be exactly identifiable by the central station(b) An extra path of communication between the central station and all local controllers(c) Direct means
7、of control of alarm and central equipment by the central station(d) Means of communication between the central station and the fire department(e) Availability of emergency power supply. The codes usually also specify the types and frequency of tests for all equipment.A fire detection and alarm syste
8、m is a combination of devices designed to signal an alarm in case of a fire. The system may also accomplish fan control, fire door hold or release, elevator recall, emergency lighting control and other emergency functions. These additional functions supplement the basic system which consists of dete
9、ction and alarm devices and central control unit. Technology has an influence on system architecture. When technology changes, the architecture has to be revised to take advantage of these changes. In recent years, VLSI technology has been advancing at an exponential rate. First NMOS and, in the las
10、t year or two, CMOS chips have been produced with the same packing density with more gates per chip yet at a lower power consumption than NMOS. Surely this change in technology must affect our design of hardware at both the chip and the system level. At the chip level, single chips are now being pro
11、duced which are equivalent to board levels of only the previous year or two. These chips have microprocessor, memory in RAM and ROM, IO Ports both serial and parallel, A/D timer, flags and other functions on chip. At the system level, the new chips make new architectures possible. The objective of t
12、his paper is to show how technology can influence system architecture in the field of fire control. The new high density single chip microcontrollers are incorporated in the design of a large scale system and yet we obtain a smaller system with a better performance. In terms of fire detection and al
13、arm monitoring, this is reflected directly in the local station hardware, because of their remoteness and power supply requirements. A complete local station can be designed around a single CMOS chip with power consumption of a few m W depending on system operation. This approach reduces the cost an
14、d complexity of design, implementation and maintenance and provides easily expandable and portable design. This implementation was not possible with old technology. Most of fire detection/monitoring systems available are tailored towards a specific application and lack the use of recent advances in
15、CMOS VLSI technology. In this study, we develop a fire detection/monitoring system which is general in concept, readily implementable in a multitude of applications for early detection of a fire before it becomes critical, for equipment and evacuation of personnel. Here, we propose a central control
16、 and distributed control/detection/monitoring with adequate communication, where use is made of single-chip microcontrollers in the local stations, thus improving controllability and observability of the monitoring process.2 Detection and alarm devicesA basic fire detection system consists of two pa
17、rts, detection and annunciation. An automatic detection device, such as a heat, smoke or flame detector, ultraviolet or infrared detectors or flame flicker, is based on detectingthe byproduct of a combustion. Smoke detectors, of both ionization and optical types, are the most commonly useddetector d
18、evices. When a typical detector of this type enters the alarm state its current consumption increasesfrom the pA to the mA range (say, from a mere 15pA in the dormant mode to 60 mA) in the active mode. Inmany detectors the detector output voltage is well defined under various operating conditions, s
19、uch as thosegiven in Table 1. The more sensitive the detector, the more susceptible it is to false alarms. In order to control the detector precisely, either of the following methods is used: a coincidence technique can be built into the detector, or a filtering technique such that a logic circuit b
20、ecomes active only if x alarms are detected within a time period T. The detection technique depends greatly on the location and plant being protected; smoke detectors are used for sleeping areas, infrared or ultraviolet radiation are used when flammable liquids are being handled, heat detectors are
21、used for fire suppression or extinguishing systems. In general, life and property protection have different approaches.Alarm devices, apart from the usual audible or visible alarms, may incorporate solid state sound reproduction and emergency voice communication or printers that record time, date, l
22、ocation and other information required by the standard code of practice for fire protection for complex plants. Heaviside 4 has an excellentreview of all types of detectors and extinguisher systems.2.1 Control philosophy and division of labourOur control philosophy is implemented hierarchically. Thr
23、ee levels of system hierarchy are implemented, with two levels of decision making. There is no communication between equipment on the same level. Interaction between levels occurs by upwards transfer of information regarding the status of the subsystems and downwards transfer of commands. This is sh
24、own in Fig. 1 where at level 1 is the central station microcomputer and is the ultimate decision maker (when not in manual mode). At level 2 are the local controllers, which reside in the local stations. At level 3 are the actual detectors and actuators. A manual mode of operation is provided at all
25、 levels.Information regarding the status of all detectors is transmitted on a per area basis to the local controllers. Their information is condensed and transmitted upward to the central microcomputer. Transfer of status is always unidirectional and upwards. Transfer of commands is always unidirect
26、ional and downwards, with expansion at the local control level. This approach preserves the strict rules of the hierarchy for exact monitoring detection and alarm systems associated with high risk plants.The classification of the two layers of controls is based upon layers of decision making, with r
27、espect to the facts that(a) When the decision time comes, the making and implementation of a decision cannot be postponed(b) The decisions have uncertainty(c) It will isolate local decisions (e.g. locally we might have an alarm although there may be a fault with the system)3 General hardwareI :Fig.
28、2 depicts our design in the simplest of forms. The system uses an open party line approach with four conductor cables going in a loop shared by all the remote devices and the control panel. This approach is simple in concept and is economically feasible. However, one major disadvantage is the depend
29、ency on a single cable for power and signaling. In cases where reliability is of extreme importance, two or even three cables taking differentroutes throughout the system may be connected in parallel. Fig. 3 gives the driver circuitry required to derive an expandable bus. This design takes advantage
30、 of recent advances in the single chip microcomputer technology to reduce the interface between the central station and the local stations.3. 1 Central control taskA central unit provides a centralized point to monitor and control the system activities. In the system to be described the central cont
31、rol unit serves a fivefold purpose.(i) It receives information from the local stations and operates the alarms and other output devices.(ii) It notifies the operator in case of system malfunction.(iii) It provides an overall system control manual and automatic.(iu) It provides a system test point of
32、 local stations and itself.(u) It provides a central point for observation, learning and adaptation.3.2 Local stationsThe local stations can take local decisions regarding recognition of a risk situation, and act independently on local affairs. In this technique we depend on load-type coordination,
33、e.g. the lower level units recognize the existence of other decision units on the same level; the central or the top level provides the lower units with a model of the relationship between its action and the response of the system.It is evident that a powerful machine is required at this stage so th
34、at all the required functions can be implemented. The availability of the new generation of microchips makes this architecture a feasible solution.A single chip microcomputer was chosen over discrete digital and analogue devices to interface to the field devices and to the central microcomputer. Thi
35、s is the main reason that previously this approach was not feasible.In selecting the microcomputer for the local stations, the criterion was the requirement for a chip which contains the most integration of the analogue and digital ports required for the interface and the utilization of CMOS technol
36、ogy owing to remoteness of the local stations. The choice was the Motorola 68HC11A4, for the following reasons:(a) It is CMOS technology; this reduces power consumption.(b) It has a UART on board; this facilitates serial communication.(e) It has an a/d converter on board; this eliminates an external
37、 A/D.(d) It has 4K of ROM, 256 bytes of RAM, 512 bytes of EERROM with 40 1/0 lines and a 16 bit timer; this satisfied all our memory and 1/0 requirements at the local station side.4 System implementationThe local station: Fig. 3 is the block diagram of the circuit used to utilize the MC68HCllA4 as a
38、 remote fire detecting circuit while Fig. 4 illustrates the same circuit in an expanded form. It can be seen that the single microcontroller can be used to monitor more than one detector, thus reducing system cost.The loop power supply, which is usually between 28 and 26 V, is further regulated by a
39、 5 V 100 mA monolithic low power voltage regulator to supply power to the microcontroller. The onboard oscillator, coupled with an external crystal of 2.4576 MHz, supplies the microcontroller with its timing signal which is divided internally by four to yield a processor frequency of 614.4 kHz, whic
40、h is an even multiple of the RS 232 7 baud rate generator. In this Section the term supervised input or output will be used to mean that the function in question is monitored for open- and short-circuit conditions in addition to its other normal functions. More information can be found in Reference
41、9.5 Main loop6 ConclusionThis paper describes the development of a large scale fire detection and alarm system using multi-single chip microcomputers. The architecture used is a two-level hierarchy of decision making. This architecture is made possible by the new CMOS microcontrollers which represen
42、t a high packing density at a low power consumption yet are powerful in data processing and thus in decision making. Each local station could make an autonomous decision if the higher level of hierarchy allows it to do so. It has been tried to keep the system design in general format so it can be ad
43、apted to varying situations. A prototype of the described system has been built and tested 10. The control part of the central station is implemented with a development card based on MC 68000 microprocessor (MEX 68KECB, by Motorola), which has a built-in monitor called Tutor. The application program
44、s were developed using the features provided by this monitor. The local stations controllers were designed using the MC 68705R3, single-chip microcontroller.7 References1 Fire protection guidelines for nuclear power plants, US NRC Regulatory Guide 1.1202 BAGCHI, C.N.: A multi-level distributed micro
45、processor system for a nuclear power plant fire protection system controls, monitoring, and communication, IEEE Trans., 19823 PUCILL, P.M.: Fire hazard protection, detection and monitoring systems, Sea. Con, 2, Proceedings of Symposium on ADV in offshore and terminal measurement and control systems,
46、 Brighton, England, March 1979, pp. 353-3634 HEAVISID, L.: Offshore fire and explosion detection and fixed fire. Offshore Technological Conference, 12th Annual Proceedings, Houston, Texas, May 1980, pp. 509-5225 CELLENTANI, E.N., and HUMPHREY, W.Y.: Coordinated detection/communication approach to fi
47、re protection, Specify: Eng.,6 Motorola Microprocessors Data Manual (Motorola Semiconductor Products, Austin, Texas, USA)7 Electronic Industries Association : Interface between data terminal equipment and data communication equipment employing serial binary data interchange (EIA Standard RS-232, Was
48、hington, DC, 1969)8 MESAROVIC, M.D., MACKO, D., TAKAHARA, Y.: Theory of hierarchical multilevel systems (Academic Press, 1970)9 KASSEM, M.: Fire alarm systems, MSc. thesis, Dept. of Elec. & Comp. Eng., Concordia University, Montreal, Canada, 198510 LIE, P., and KOTAMARTI, U.: The design of a fire al
49、arm system using microprocessors, C481 Project, Dept. of Elec. and Comp. Eng., Concordia University, Montreal, Canada, 1986译文基于单片机的火灾探测和监控系统A.J. AI-Khalili, MSc, PhDD. AI-Khalili, MSc, PhDM.S. Khassem, MSc关键词：危险，设计，设备状态监测摘要：火灾探测及报警监控已成为一个复杂而完整的体系。该系统采用多个单芯片架构到一条主线上。该控制算法是基于两级决策层次，因此分配了复杂性。一个完整的电路原理图，给出了主、分控制器所需的软件的结构要求。设计延续一般形式，这样可以适应于多种系统