火灾报警器中英文文献翻译.docx

1、火灾报警器中英文文献翻译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 has

2、 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 wit

3、h 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 comp

4、lexity 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 Detection and alarm devicesA basic fire detection system consists of two p

5、arts, 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

6、devices. 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,

7、such 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

8、becomes 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

9、 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,

10、location 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.1.1 Control philosophy and division of labourOur control philosophy is implemented hierarchically. Th

11、ree 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 s

12、hown 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 al

13、l 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 unidirec

14、tional 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

15、respect 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)2 General hardwareI :Fig.

16、 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 depen

17、dency 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 advantag

18、e of recent advances in the single chip microcomputer technology to reduce the interface between the central station and the local stations.2. 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 con

19、trol 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 o

20、f local stations and itself.(u) It provides a central point for observation, learning and adaptation.2.2 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,

21、 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 t

22、hat 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. Th

23、is 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 techno

24、logy 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 externa

25、l 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.3 System implementationThe local station: Fig. 3 is the block diagram of the circuit used to utilize the MC68HCllA4 as

26、a 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

27、a 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, whi

28、ch 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

29、 9.4 Main loop5 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 represe

30、nt 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 a

31、dapted 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 progra

32、ms 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 microprocessor 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