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Training for the Planning of Large-Scale Control Systems
Copyright © IFAC Training for Tomorrow Leiden, The Ne therlands, 1983
TRAINING FOR THE PLANNING OF LARGESCALE CONTROL SYSTEMS A. Caballero* and Aleksander Shashkin** *Automatic Control Dept., ISPjAE, Havana, Cuba **Radio Equtpments of Shtps Dept. , Electrotechnical Institute of Leningrad, USSR
Abstract. A methodology for the designing 2nd implementation of large-scale control systems is discussed. There are included theoretical questions supported by a sequence of practical works, carried out in a special laboratory conceived in order to give a complete training for planning or implementation of such systems. Keywords. Large-scale systems; telecontrol; learning systems; educational aids. INTRODUCTION The planning and implementation of large-scale control systems present its own characteristics. It is necessary to take into account the location of the directed objects in a big area. This implicates the introduction of special techniques and equipments for a long distance information transmission and the employment of interfases in order to communicate the computer with the communication channel. All this increases the complication in designing such systems in comparison with other computer or automation systems. Training, directed to the attainment of abilities in planning large-scale control .systems, allows the obtainment of the necessary abilities for planning on the basis of the employment of modelling programs and equipments. The selected models must be related in a direct manner to the physical processes and systems represented by them. The paper presents a methodology for the designig and implementation of large-scale control systems on the basis of the study of a real system. The methodology includes theoretical questions supported by a sequence of practical works, carried out in a special laboratory conceived in order to give a complete training for planning or implementation of such systems.
D8SCRIPTION OF THE SYST8M The proposed system as a model permits the study of all the properties that defines the typical large-scale control systems. The selected model is the telecontrol system of water distribution in Havana City, and the methodology is based in the project of such a system. The water distribution for aproximately 2 million persons is performed from a group of sources, distributed in 10 000 Ha. It is necessary to telemeter more than 200 parameters which include pressure, level and water flow and the telecontrol of 130 pump stations. The proposed system has a hierarchical structure with three control levels (fig. 1). In the third level one has a dispatcher directed by the computer. In the second level there are ten control centers. The communication is performed almost exclusively by means of radio channels. In order to have a correct image of all the stages in the project, it is necessary to include the technical parameters of the controlled system and the geographical situation of all its con~tituents. For example, the situation of the controlled objects serves as a basis for the selection of the frequency band in the communication channel. The proposed system possesses all the necessary constituents to state and to solve the following problems:
78
A. Caballero and A. Shashkin
- to state the finality and principal functions of the system; structure analysis and its optimization methods with the aid of a computer; - study of equipments for the elaboration and representation of information; analysis of the telecontrol and telemetering signals transmission channels; -
~tudy of the logical decision circuits; - analysis of differents measuring methods and transducers implementation; study of methods for eVuluation of reliability of the equipments and failure diagnosis. There is a set of systems that can be studied starting from the presented aspects. For example: irrigation control systems;distribution of gas and petroleum control systems, etc.
One proposes a method to obtain this feedback: simplex messages transmission in the form "not understand" from the students to the trainer. The trainer sees at a display all this messages. The number of signals permits the trainer to know the level of understanding of the exposed subject. In this way he regulates the velocity of the explanation and repeats the more difficult subjects. There is a very simple form to obtain this system: if it is necessary, the student push a buttom to transmit one signal to the trainer display. This information is temporarely fixed at the display. The basis for the attainment of practical abilities is the work of students at the laboratory with the physical or mathematical models of the studied system. The automation of the practical works permits increase its efficiency. The employment of a microcomputer at the trainer seat give a set of new possibilities in the work at laboratory. Among these are the storage and statistical elaboration of information above the training process. At fig. 2 a block diagram is presented. Within thr pointed line is showed the equipments at the trainer seat. Each student seat is connected with the trainer seat by a radiochannel.
Fig. 1 Hierarchical structure of the telecontrol system TRAINING PROCESS It is possible to diferentiate two aspects in the training process: 1) attainment of theoretical knowledge; 2) attainment of practical abilities. The teaching of theoretical knowledge is carried out basically in the lecture mode. One inconvenient of this method is the absence of feedback from the student to the trainer. All the traditionally employed methods (questions or control works) increase the employed time.
Fig. 2 Employment of a microcomputer in the training process. 1- Program file; 2- CPU; 3- input-output peripherals at the trainer seat; 4- timcshared network; 5- input-output peripherals at the students seats.
Training for Planning
The automated control of the student work permits a more directed trainer work at the laboratory: the instructor knows in a more effective manner the students difficulties in obtaining practical abilities and with the employment of a set of developed programs it is possible to determine the less elaborate subjects. Furthermore, the automated control system permits the study at the laboratory level of a developed system for interchange of information between a control centre (trainer seat) and a number of controlled stations (students seats). Before the realization of each practical work, students have to answer a set of question related with: theory about the studied subject; knowledge about the measurement equipments; knowledge about the student seat peri pheri cals. The students answer the questions from its seats and this answers will be coded and transmited to the trainer seat. The trainer has at his seat a display to represent the students answers with the correspondent address. It is usefull to include also a printer for getting a copy of the students work information. CONCLUSIONS 1. The employment of a real physical system give the possibility of studing all the necessary subjects in the training process, because this model has all the elements presented in the majority of large-scale control systems. 2 . Feedback automation of lectures permits a better employment of time. 3. The automated control system at the laboratory increases the efficiency of the training process and permits a more individually work with stUdents.
79
REFERENCES -Caballero, A.; A. Shashkin (1982). Sistema automatizado para la direccion de la distribucion de agua. III Ciclo de Conferencias Cientificas del ISPJAE. -Lopez Bru, J. (1979) Ensenanza programada asistida por ordenadores. Rev. Mundo Electronico, 87,51-55. -Dirksen, A.J. (Ed. 1979), Microcomputers. Kluwer technische boeken by Deventer-Antwerpen.
TRAINING FOR THE PLANNING OF LARGESCALE CONTROL SYSTEMS A. Caballero* and Aleksander Shashkin** *Automatic Control Dept., ISPjAE, Havana, Cuba **Radio Equtpments of Shtps Dept. , Electrotechnical Institute of Leningrad, USSR
Abstract. A methodology for the designing 2nd implementation of large-scale control systems is discussed. There are included theoretical questions supported by a sequence of practical works, carried out in a special laboratory conceived in order to give a complete training for planning or implementation of such systems. Keywords. Large-scale systems; telecontrol; learning systems; educational aids. INTRODUCTION The planning and implementation of large-scale control systems present its own characteristics. It is necessary to take into account the location of the directed objects in a big area. This implicates the introduction of special techniques and equipments for a long distance information transmission and the employment of interfases in order to communicate the computer with the communication channel. All this increases the complication in designing such systems in comparison with other computer or automation systems. Training, directed to the attainment of abilities in planning large-scale control .systems, allows the obtainment of the necessary abilities for planning on the basis of the employment of modelling programs and equipments. The selected models must be related in a direct manner to the physical processes and systems represented by them. The paper presents a methodology for the designig and implementation of large-scale control systems on the basis of the study of a real system. The methodology includes theoretical questions supported by a sequence of practical works, carried out in a special laboratory conceived in order to give a complete training for planning or implementation of such systems.
D8SCRIPTION OF THE SYST8M The proposed system as a model permits the study of all the properties that defines the typical large-scale control systems. The selected model is the telecontrol system of water distribution in Havana City, and the methodology is based in the project of such a system. The water distribution for aproximately 2 million persons is performed from a group of sources, distributed in 10 000 Ha. It is necessary to telemeter more than 200 parameters which include pressure, level and water flow and the telecontrol of 130 pump stations. The proposed system has a hierarchical structure with three control levels (fig. 1). In the third level one has a dispatcher directed by the computer. In the second level there are ten control centers. The communication is performed almost exclusively by means of radio channels. In order to have a correct image of all the stages in the project, it is necessary to include the technical parameters of the controlled system and the geographical situation of all its con~tituents. For example, the situation of the controlled objects serves as a basis for the selection of the frequency band in the communication channel. The proposed system possesses all the necessary constituents to state and to solve the following problems:
78
A. Caballero and A. Shashkin
- to state the finality and principal functions of the system; structure analysis and its optimization methods with the aid of a computer; - study of equipments for the elaboration and representation of information; analysis of the telecontrol and telemetering signals transmission channels; -
~tudy of the logical decision circuits; - analysis of differents measuring methods and transducers implementation; study of methods for eVuluation of reliability of the equipments and failure diagnosis. There is a set of systems that can be studied starting from the presented aspects. For example: irrigation control systems;distribution of gas and petroleum control systems, etc.
One proposes a method to obtain this feedback: simplex messages transmission in the form "not understand" from the students to the trainer. The trainer sees at a display all this messages. The number of signals permits the trainer to know the level of understanding of the exposed subject. In this way he regulates the velocity of the explanation and repeats the more difficult subjects. There is a very simple form to obtain this system: if it is necessary, the student push a buttom to transmit one signal to the trainer display. This information is temporarely fixed at the display. The basis for the attainment of practical abilities is the work of students at the laboratory with the physical or mathematical models of the studied system. The automation of the practical works permits increase its efficiency. The employment of a microcomputer at the trainer seat give a set of new possibilities in the work at laboratory. Among these are the storage and statistical elaboration of information above the training process. At fig. 2 a block diagram is presented. Within thr pointed line is showed the equipments at the trainer seat. Each student seat is connected with the trainer seat by a radiochannel.
Fig. 1 Hierarchical structure of the telecontrol system TRAINING PROCESS It is possible to diferentiate two aspects in the training process: 1) attainment of theoretical knowledge; 2) attainment of practical abilities. The teaching of theoretical knowledge is carried out basically in the lecture mode. One inconvenient of this method is the absence of feedback from the student to the trainer. All the traditionally employed methods (questions or control works) increase the employed time.
Fig. 2 Employment of a microcomputer in the training process. 1- Program file; 2- CPU; 3- input-output peripherals at the trainer seat; 4- timcshared network; 5- input-output peripherals at the students seats.
Training for Planning
The automated control of the student work permits a more directed trainer work at the laboratory: the instructor knows in a more effective manner the students difficulties in obtaining practical abilities and with the employment of a set of developed programs it is possible to determine the less elaborate subjects. Furthermore, the automated control system permits the study at the laboratory level of a developed system for interchange of information between a control centre (trainer seat) and a number of controlled stations (students seats). Before the realization of each practical work, students have to answer a set of question related with: theory about the studied subject; knowledge about the measurement equipments; knowledge about the student seat peri pheri cals. The students answer the questions from its seats and this answers will be coded and transmited to the trainer seat. The trainer has at his seat a display to represent the students answers with the correspondent address. It is usefull to include also a printer for getting a copy of the students work information. CONCLUSIONS 1. The employment of a real physical system give the possibility of studing all the necessary subjects in the training process, because this model has all the elements presented in the majority of large-scale control systems. 2 . Feedback automation of lectures permits a better employment of time. 3. The automated control system at the laboratory increases the efficiency of the training process and permits a more individually work with stUdents.
79
REFERENCES -Caballero, A.; A. Shashkin (1982). Sistema automatizado para la direccion de la distribucion de agua. III Ciclo de Conferencias Cientificas del ISPJAE. -Lopez Bru, J. (1979) Ensenanza programada asistida por ordenadores. Rev. Mundo Electronico, 87,51-55. -Dirksen, A.J. (Ed. 1979), Microcomputers. Kluwer technische boeken by Deventer-Antwerpen.