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MERCEDES — Interactive Software Package for Identification and Experimental Control of Industrial Plants by a Portable Process Computer Laboratory
MERCEDES INTERACTIVE SOFTWARE PACKAGE FOR IDENTIFICATION AND EXPERIMENTAL CONTROL OF INDUSTRIAL PLANTS BY A PORTABLE PROCESS COMPUTER LABORATORY A. Feher, N. Czeiner, Z, Csaszar, A. Turi, L. Keviczky*, R. Bars*, R. Haber*, M. Habermayer*, J. Hetthessy*, I. Vajk* and M. Vajta, Jr* Research Group for Automation, Institute for Research and Planning in Silicate Industry, Budapest, Hungary *Department of Automation, Technical University of Budapest, Budapest, Hungary
Abstract.
The paper describes the ~mRCEDES program-package for industrial applications. The interactive semigraphical system can be operated in a portable process computer laboratory. It contains a process control, an off-line identification and a controller-design program package. su~t8ble
Keywords.
Process control, interactive software package.
INTRODUCTION
Planning in Silicate Industry. The equipments are built into a special trailer. The main components are as follows:
The program system MERCEDES (Moving computER Control and procEss iDentification System) to be presented was designed to satisfy industrial requirements for solving industrial problems. In 1974 the Institute for Research and Planning in Silicate Industry set up a so-called Portable Process Computer Laboratory (PPCL) for solving control tasks arising in the cement, oeramio and glass factories in Hungary. Data logging, monitoring and oontrol programs were developed for several tasks.
a TPA-i digital computer of 24 kbyte (similar to the PDP 8), a disc and floppy-disos, standard peripheries (paper-tape reader and puncher, matrixprinter, display, teletype, etc.h CAMAC process peripheries. The applied languages were FORTRAN for off-line computations and OPAL for real-time tasks. The main features of the elaborated processcontrol program-package are:
After the initial phase - when already industrial tasks were solved suocessfully - the olaim for elaborating a uniform oontrol programpaokage arose. This paokage was designed by the oommon team of the University and the Researoh Institute acoording to concrete experiences gained so far, to other systems described in the literature (SOCOCO, 1976) and to the existin~ and expectable demands of the silicate industry.
it was designed for industrial purposes, it is user oriented, it contains the oontrol algorithms for the tasks defined by the technology, it is of modular construotion, for a given task only the necessary modules are to be used, for fundamental tasks (e.g. monitoring, identification, control) programs are also available, a general program for oomplex control tasks is available, the system can be completed at any time by additional modules written in a high level language with a machine-independent syntaxis,
THE MERCEDES PROGRAM SYSTEM The Portable Process Computer Laboratory was realized by the Central Research Institute for Physics and the Institute for Research and 261
A. Fe her et al .
262
it is interactive, the results are generally displayed graphically (e.g. unit step responses, measured and estimated output signals, etc.), the interactive dialogues are easily understable and supplied with comments, the assignation of the peripheries makes possible the operation both from the PPCL and the display fitted into the control desk of the plant.
the individual functions. Then the RT modules operate by sampling periods. After the passage of a preset timeperiod the OF module - whose execution depends on the operators's command - appears periodically. The offline interactive evaluation practically does not disturb the real-time modules, since the background snaps are interrupted during the real-time computations. BACKGROUND
The process-control program-package attains the above properties by utilizing algorithms, known from the international technical literature and proved in practice. The programpackage consists of three main parts:
2. DALO
3. NOLID 4. DDC 5. ST
6. TEGE 1. INVE
8. DEVAL
9. INT
and Modification module, - DAta Lagging module, - NOnlinear On-Line IDentification module, - Direct Digital Control module, - Self-Tuning minimum variance control module, - TEst signal GEnerator module, - INterVEntion module, - Data EVALuation module, - INTerrupt module.
The scheme of the RTP system is seen in Fig. 1. The meaning of the letters with hyphens beside the program names 1s: IM RT OF
- initialization and modification module, - real-time operation module, - off-line operation module.
The initialization of the systems is followed by the initialization of
1
I
1
I
-
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RjPl,
1
=f===t=~11
1
I
1
-L~I=~==~I C=~
1
____~______.~_ __ _~
I
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I I 1
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Fig. 1.
1. SYS-IM - SYStem Initialization
I
~~r- ·-· - · - - I - - - - - ~- - · - - - - -j- - - ·
Real-Time process-control Program system, 2. OLIP: Off-Line Identification Program-system, 3. OCAD: Off-line program-system for Computer Aided Design of the controller.
The task of the RTP is to establish direct connection with the process and the creation of the double oriented signal flow (measurement, data logging and intervention), processing of the collected data, primary evaluation (monitoring, etc.) modelling and the realization of discrete control algorithms. The parts of the system are:
FOREGROUND
I
1. RTP:
RTP - REAL-TIME PROCESSCONTROL PROGRAli-PACKAGE
I
Structure of the Real-Time Package.
The tasks of the DALO module are as follows: data collection, credibility test (statical and dynamical) dimensioning, i.e. conversion into physical quantities in the knowledge of the concrete measurement process and the parameters of the measuring eqUipment, evaluation of the measurement error and noise filtering (filtering time lage elements, moving average, weighting, etc.), writing data into the common, to diSC, paper-tape or line-printer. The module NOLID is suitable for real-time identification of static and dynamic, linear and nonlinear, single and multi-input processes. The utilized identification method is a two-step method: it consists of a correlation-computation and a 1eastsquares parameter-estimation. This process is an appropriate tool fo: the real-time interactive evaluat1on, as the correlation functions are updated recursively in a rhythm dictated by the data collection, and the interactive - off-line - evaluation permits the quick choice of the appropriate model components, the order and dead time. ~e DDC module contains control algorithms of rational fractional function forms, realizing discrete PID
MERCEDES-Interactive software package
263
and dead beat control algorithms respectively, suitable to control the SISO, MISO and MIMO systems with known parameters.
The module COpy realizes the transmission between several peripheries and files. The transmission corresponds to the type of the file.
The ST module contains a control algorithm, adapting to the changes of the system and the noise parameters. It is suitable to control SISO, MISO and ~MO systems. The algorithm keeps the des i red output signal at its prescribed value with mimimum variance.
With the help of the CORRECTION module the library and any user file can be corrected or modified.
The task of the TEGE module is to set the appropriate working steps and changes according to a given time-plan necessary for the qualitative modelling of the system, as well as the generation of the excitation indispensable important for the identification processes. The task of the INVE module is to issue the intervention signals calculated by the RT modules. The task of the DEVAL module is the primary evaluation of the measured and calculated data. Its services are as follows: the statistical evaluation of the data (average variance and extent calculation~ observing of the limit value overshuts, compiling of detailed and summarized journals, graphical displaying of signal changes etc. The INT module serves the program interruptions arriving from the technological process and the operator. It identifies the programinterruptions, then executes the tasks assigned to the interruptions caused by modifications of the program-run, by special Signals depending on the technology etc. OLIP OFF-LINE IDENTTFICATION PROGRAM-PACKAGE The task of OLIP is: model-building and identification on the basis of the collected measurement data. The OLIP and the RTP systems intercommunicate through the disc files. The user of the OLIP system can select from the following "menu": O. 1. 2.
3. 4.
5. 6.
7. 8.
9.
STOP COpy CORRECTION TRANSFORMATION IDENTIFICATION DRAWING FILTER Z-S TRANSFORMATION ~. CONTROLLER TEST
The TRANSFORMATION module produces from a given file a new, transformated file. The IDENTIFICATTON module estimates the parameters of multi-input multioutput, linear and nonlinear, static and dynamic systems. The DRAWING module is suitable for displaying time functions, correlation finctions and denSity functions. The FILTER module produces new files by a filter of given structure and parameters. The Z-S TRANSFORMATION module determines the equivalent continuous equation of a discrete system by bilinear transformation. The MY. CONTROLLER module designs a controller ensuring the minimum variance of the controlled variable. The TES T module is a simulator which permits the testing of OLIP. OCAD OFF-LINE CONTROLLER DES I GNING PROGRAM-PACKAGE The task of OCAD is to des i gn a controller in the knowledge of the system model obtained by RTP or OLIP. The sytem including the controller may be simulated, the input and output signal series can be displayed, supplying the technologist with a service he can interpret himself. The satisfaction of the technological restrictions may be easily checked by the time functions. The parts of the system are: 1. FRECAD - FREquency method for Computer Aided controller Design, 2. ROCAD - generalized ROot-locus method for Computer Aided controller Design, 3. INCAD INtegral criterion method for Computer Aided controller Design, 4. STOCAD - minimum variance STOchastic Computer Aided controller Design, 5. SIMCAD - time-domain SIMulator for Computer Aided controller Design.
A. Fehe r et
264
APPLICATIONS
a~.
data logging, evaluation of the data (monitoring, graphical display, average calculation, etc.), identification, controller deSign, calculation of the controller algorithm, generation of a pescribed intervention signal, intervention (reference signal, test signal, DDC, etc.) The MERCEDES program-package may be utilized in a multiple way for the solution of industrial problems. ~rimary
We utilized some module of the program system (see Fig. 2.) succesfully for data logging, identification and adaptive control at one of the furnaces of the hollow glass factory in Oroshaza (Hungary).
Fig. 2.
Control of the Glass Furnace by the PPCL.
We have elaborated a control model for the output variables: level, temperature and space pressure in the furnace. The conventional controller of the raw-material feeder required for glass-making was re~laced by a self-tuning controller CRTP-ST module), whereby we attained a lower level fluctuation and so a more uniform drop size. Figure 3. shows the scheme of the utilized control system of the glass-melting furnace.
With the spreading of the microprocessor systems a new utilization field of the Portable Process Computer Laboratory comes into the foreground. With the help of the laboratory the technologists and the control technicians can determine the local or central controller together on the site, utilizing a high level programming language and the algorithms can be optimized taking the concrete operating conditions into consideration. Later on the PPCL can be replaced by an inexpensive local analogue or digital regulator, purposefully by a microprocessor. In this way the importance of the PPCL grows beyond the field of the silicate-industry, it creates the general possibility of setting up industrial microprocessor controllers. Accordingly the hardware and software labour costs invested in the system are recovered in a short time. REFERENCES
Fig. 3.
1 st IFAC/IFIP Symposium on Software for Computer Control. SOCOCO. Tallin. USSR. May 25-28. (1976). Haber,R., J. Hetthessy, L. Keviczky, I. Vajk, A. Feher, N. Czeiner Z. CS8szar and A. Turi (1979). Identification and adaptive control of a glass furnace by a portable process computer laboratory - Case study. 5th IFAC Symposium on Identification and System Parameter Estimation, Darmstadt. (to be appeared). Application of the MERCEDES
This application will be described in detail in a future paper (Haber and co-workers, 1979). CONCLUSIONS Summarizing the MERCEDES programpackage performs the following tasks:
Abstract.
The paper describes the ~mRCEDES program-package for industrial applications. The interactive semigraphical system can be operated in a portable process computer laboratory. It contains a process control, an off-line identification and a controller-design program package. su~t8ble
Keywords.
Process control, interactive software package.
INTRODUCTION
Planning in Silicate Industry. The equipments are built into a special trailer. The main components are as follows:
The program system MERCEDES (Moving computER Control and procEss iDentification System) to be presented was designed to satisfy industrial requirements for solving industrial problems. In 1974 the Institute for Research and Planning in Silicate Industry set up a so-called Portable Process Computer Laboratory (PPCL) for solving control tasks arising in the cement, oeramio and glass factories in Hungary. Data logging, monitoring and oontrol programs were developed for several tasks.
a TPA-i digital computer of 24 kbyte (similar to the PDP 8), a disc and floppy-disos, standard peripheries (paper-tape reader and puncher, matrixprinter, display, teletype, etc.h CAMAC process peripheries. The applied languages were FORTRAN for off-line computations and OPAL for real-time tasks. The main features of the elaborated processcontrol program-package are:
After the initial phase - when already industrial tasks were solved suocessfully - the olaim for elaborating a uniform oontrol programpaokage arose. This paokage was designed by the oommon team of the University and the Researoh Institute acoording to concrete experiences gained so far, to other systems described in the literature (SOCOCO, 1976) and to the existin~ and expectable demands of the silicate industry.
it was designed for industrial purposes, it is user oriented, it contains the oontrol algorithms for the tasks defined by the technology, it is of modular construotion, for a given task only the necessary modules are to be used, for fundamental tasks (e.g. monitoring, identification, control) programs are also available, a general program for oomplex control tasks is available, the system can be completed at any time by additional modules written in a high level language with a machine-independent syntaxis,
THE MERCEDES PROGRAM SYSTEM The Portable Process Computer Laboratory was realized by the Central Research Institute for Physics and the Institute for Research and 261
A. Fe her et al .
262
it is interactive, the results are generally displayed graphically (e.g. unit step responses, measured and estimated output signals, etc.), the interactive dialogues are easily understable and supplied with comments, the assignation of the peripheries makes possible the operation both from the PPCL and the display fitted into the control desk of the plant.
the individual functions. Then the RT modules operate by sampling periods. After the passage of a preset timeperiod the OF module - whose execution depends on the operators's command - appears periodically. The offline interactive evaluation practically does not disturb the real-time modules, since the background snaps are interrupted during the real-time computations. BACKGROUND
The process-control program-package attains the above properties by utilizing algorithms, known from the international technical literature and proved in practice. The programpackage consists of three main parts:
2. DALO
3. NOLID 4. DDC 5. ST
6. TEGE 1. INVE
8. DEVAL
9. INT
and Modification module, - DAta Lagging module, - NOnlinear On-Line IDentification module, - Direct Digital Control module, - Self-Tuning minimum variance control module, - TEst signal GEnerator module, - INterVEntion module, - Data EVALuation module, - INTerrupt module.
The scheme of the RTP system is seen in Fig. 1. The meaning of the letters with hyphens beside the program names 1s: IM RT OF
- initialization and modification module, - real-time operation module, - off-line operation module.
The initialization of the systems is followed by the initialization of
1
I
1
I
-
7 ,.r
RjPl,
1
=f===t=~11
1
I
1
-L~I=~==~I C=~
1
____~______.~_ __ _~
I
1 I I
I I 1
I L -_ __ _- ' I I
Fig. 1.
1. SYS-IM - SYStem Initialization
I
~~r- ·-· - · - - I - - - - - ~- - · - - - - -j- - - ·
Real-Time process-control Program system, 2. OLIP: Off-Line Identification Program-system, 3. OCAD: Off-line program-system for Computer Aided Design of the controller.
The task of the RTP is to establish direct connection with the process and the creation of the double oriented signal flow (measurement, data logging and intervention), processing of the collected data, primary evaluation (monitoring, etc.) modelling and the realization of discrete control algorithms. The parts of the system are:
FOREGROUND
I
1. RTP:
RTP - REAL-TIME PROCESSCONTROL PROGRAli-PACKAGE
I
Structure of the Real-Time Package.
The tasks of the DALO module are as follows: data collection, credibility test (statical and dynamical) dimensioning, i.e. conversion into physical quantities in the knowledge of the concrete measurement process and the parameters of the measuring eqUipment, evaluation of the measurement error and noise filtering (filtering time lage elements, moving average, weighting, etc.), writing data into the common, to diSC, paper-tape or line-printer. The module NOLID is suitable for real-time identification of static and dynamic, linear and nonlinear, single and multi-input processes. The utilized identification method is a two-step method: it consists of a correlation-computation and a 1eastsquares parameter-estimation. This process is an appropriate tool fo: the real-time interactive evaluat1on, as the correlation functions are updated recursively in a rhythm dictated by the data collection, and the interactive - off-line - evaluation permits the quick choice of the appropriate model components, the order and dead time. ~e DDC module contains control algorithms of rational fractional function forms, realizing discrete PID
MERCEDES-Interactive software package
263
and dead beat control algorithms respectively, suitable to control the SISO, MISO and MIMO systems with known parameters.
The module COpy realizes the transmission between several peripheries and files. The transmission corresponds to the type of the file.
The ST module contains a control algorithm, adapting to the changes of the system and the noise parameters. It is suitable to control SISO, MISO and ~MO systems. The algorithm keeps the des i red output signal at its prescribed value with mimimum variance.
With the help of the CORRECTION module the library and any user file can be corrected or modified.
The task of the TEGE module is to set the appropriate working steps and changes according to a given time-plan necessary for the qualitative modelling of the system, as well as the generation of the excitation indispensable important for the identification processes. The task of the INVE module is to issue the intervention signals calculated by the RT modules. The task of the DEVAL module is the primary evaluation of the measured and calculated data. Its services are as follows: the statistical evaluation of the data (average variance and extent calculation~ observing of the limit value overshuts, compiling of detailed and summarized journals, graphical displaying of signal changes etc. The INT module serves the program interruptions arriving from the technological process and the operator. It identifies the programinterruptions, then executes the tasks assigned to the interruptions caused by modifications of the program-run, by special Signals depending on the technology etc. OLIP OFF-LINE IDENTTFICATION PROGRAM-PACKAGE The task of OLIP is: model-building and identification on the basis of the collected measurement data. The OLIP and the RTP systems intercommunicate through the disc files. The user of the OLIP system can select from the following "menu": O. 1. 2.
3. 4.
5. 6.
7. 8.
9.
STOP COpy CORRECTION TRANSFORMATION IDENTIFICATION DRAWING FILTER Z-S TRANSFORMATION ~. CONTROLLER TEST
The TRANSFORMATION module produces from a given file a new, transformated file. The IDENTIFICATTON module estimates the parameters of multi-input multioutput, linear and nonlinear, static and dynamic systems. The DRAWING module is suitable for displaying time functions, correlation finctions and denSity functions. The FILTER module produces new files by a filter of given structure and parameters. The Z-S TRANSFORMATION module determines the equivalent continuous equation of a discrete system by bilinear transformation. The MY. CONTROLLER module designs a controller ensuring the minimum variance of the controlled variable. The TES T module is a simulator which permits the testing of OLIP. OCAD OFF-LINE CONTROLLER DES I GNING PROGRAM-PACKAGE The task of OCAD is to des i gn a controller in the knowledge of the system model obtained by RTP or OLIP. The sytem including the controller may be simulated, the input and output signal series can be displayed, supplying the technologist with a service he can interpret himself. The satisfaction of the technological restrictions may be easily checked by the time functions. The parts of the system are: 1. FRECAD - FREquency method for Computer Aided controller Design, 2. ROCAD - generalized ROot-locus method for Computer Aided controller Design, 3. INCAD INtegral criterion method for Computer Aided controller Design, 4. STOCAD - minimum variance STOchastic Computer Aided controller Design, 5. SIMCAD - time-domain SIMulator for Computer Aided controller Design.
A. Fehe r et
264
APPLICATIONS
a~.
data logging, evaluation of the data (monitoring, graphical display, average calculation, etc.), identification, controller deSign, calculation of the controller algorithm, generation of a pescribed intervention signal, intervention (reference signal, test signal, DDC, etc.) The MERCEDES program-package may be utilized in a multiple way for the solution of industrial problems. ~rimary
We utilized some module of the program system (see Fig. 2.) succesfully for data logging, identification and adaptive control at one of the furnaces of the hollow glass factory in Oroshaza (Hungary).
Fig. 2.
Control of the Glass Furnace by the PPCL.
We have elaborated a control model for the output variables: level, temperature and space pressure in the furnace. The conventional controller of the raw-material feeder required for glass-making was re~laced by a self-tuning controller CRTP-ST module), whereby we attained a lower level fluctuation and so a more uniform drop size. Figure 3. shows the scheme of the utilized control system of the glass-melting furnace.
With the spreading of the microprocessor systems a new utilization field of the Portable Process Computer Laboratory comes into the foreground. With the help of the laboratory the technologists and the control technicians can determine the local or central controller together on the site, utilizing a high level programming language and the algorithms can be optimized taking the concrete operating conditions into consideration. Later on the PPCL can be replaced by an inexpensive local analogue or digital regulator, purposefully by a microprocessor. In this way the importance of the PPCL grows beyond the field of the silicate-industry, it creates the general possibility of setting up industrial microprocessor controllers. Accordingly the hardware and software labour costs invested in the system are recovered in a short time. REFERENCES
Fig. 3.
1 st IFAC/IFIP Symposium on Software for Computer Control. SOCOCO. Tallin. USSR. May 25-28. (1976). Haber,R., J. Hetthessy, L. Keviczky, I. Vajk, A. Feher, N. Czeiner Z. CS8szar and A. Turi (1979). Identification and adaptive control of a glass furnace by a portable process computer laboratory - Case study. 5th IFAC Symposium on Identification and System Parameter Estimation, Darmstadt. (to be appeared). Application of the MERCEDES
This application will be described in detail in a future paper (Haber and co-workers, 1979). CONCLUSIONS Summarizing the MERCEDES programpackage performs the following tasks: