Interactive computer programs for education and research: A survey

Vol. 15, pp. 113 121 Pergamon PressLtd. 1979. Printedin Great Britain © hxlclI~;itiL~nalFederationof AutomaticControl

Automatica

Interactive Computer Programs for Education and Research: A Survey* W. J. M. L E M M E N S t and A. J. W. VAN D E N B O O M t Key Word Index-- Computer programming; interactive programs; software packages; education; educational aids; modelling.

C. To provide a possibility to compare methods e.g. identification methods. D. To fiaake new developments of control theory available for a large group of users. E. To save students' time by providing existing software which obviates time consuming calculations and graph plotting by hand.

Summary--In this paper, a survey is given of the development and use of interactive computer packages for education and research in the field of control engineering, signal analysis and parameter estimation. Relevant aspects are: aims and goals of the package, its design and structure, the interaction, the development of the software, the necessary hardware, the educational aspects, the contents of.lhe package and possible future developments. 1. I N T R O D U C T I O N

Programming and computer science

DURING the last five years, an increasing interest in interactive computer programs may be noticed at almost all control institutes. Mostly these programs are developed by the institutes themselves for educational purposes or as a tool for researchers. In this survey we intend to analyse the relevant aspects of this type of development. These aspects are: aims and goals of the package, its design and structure, the interaction, the necessary hardware, the educational aspects, the contents of the package and possible future developments. 2. PURPOSES,

AIMS AND MOTIVATIONS INTERACTIVE SYSTEMS

F.

To make possible use of computers for automatic control problems with minimal or no knowledge of programming and computer science. G. To encourage use of well proven, stable and robust numerical software. H. To create the possibility of writing software parts without regard for context (for students cooperating in the development of the package). I. To create a possibility for 'real-time' processing. J. To introduce students to possibilities, and problems, of interfacing computers to processes.

OF

There are several converging reasons for constructing an interactive system. Most of them are valid for the majority of systems that have been developed.

The requirements for an interactive program can be specified as follows: A. Modular form of the whole set-up. This facilitates changes and extensions and gives a clearer insight into the structure of the package. B. Flexibility. Changes, additions, extensions have to be easily done. Users should be offered flexibility in use. C. Portability. The dependency on a specific configuration should be as limited as possible. D. Visual output, comparable with t e x t b o o k - and course diagrams. E. Multi-user facility. This provides a better availability for users and a more efficient use of the hardware. F. Separation between control software and the interactive--and organisational part of the software. G. Documentation.

Control theory A. To instruct students in aspects of modern control theory that need the use of a computer. B. To create a library facility for control software and provide a means by which results of one program can be used or analyzed by another. *Received January 3, 1978; revised July 14, 1978. The original version of this paper was presented at the IFAC Symposium on Trends in Automatic Control Education which was held in Barcelona, Spain during March/April 1977. The published preprints of this IFAC Meeting may be ordered from: Comite Espanol de la IFAC, Via Layetana 39, Barcelona 3, Spain. This paper was recommended for publication in revised form by associate editor B. Gaines. tEindhoven University of Technology, E.E. Dept., Group Measurement and Control, P.O. Box 513, Eindhoven, Netherlands. 113

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W.J.M.

LEMMENS and A. J. W. VAN J)CN BOOM

H. Self explanation. This reduces reading manuals or handbooks. I. Logbook. This is produced on behalf of the user to help him to work out his results for reports etc. 3. E D U C A T I O N A L ASPECTS

In this section we will discuss the educational implications of the use of an interactive system in the educational process. The relevant aspects are: possible contributions of a interactive system to the educational process, the type of use during the different phases of the education, the experience with interactive systems gained at different institutes and the involvement of students in the development of the package.

but a support for insight! Limited time is awiilable in the curriculum for the control courses. This means it should be used efficiently. An interactive facility can help to save time which otherwise would be spent on long and tedious calculations or programming and debugging work. Programming has to be taught in other courses and can be exercised in graduate and postgraduate work for more specific projects. Due to the time saving property the following features can be stressed: concentration on control theory (deepening of the insight) acquiring skill in the application of theory (broader ability) broader use of different methods (wider scope).

3.1. Role of the interactive system in the educational process

3.2. Use of the package during different phases q['

An interactive system is a new tool, with specific contributions to the educational process. Due to the feature of interaction, it can provide a great deal of flexibility in use. During class demonstrations it illustrates a variety of aspects of the technique under consideration and it resolves the problems which arise a m o n g the students during the session. This means that the course will have a vivid and dynamic character, as it is concentrated around the difficulties with the material as felt by the students. It will be obvious that such a session is difficult to preprogram. Another important aspect of the use of interactive systems is the possibility to show the power and limitations of existing analytical techniques. This can contribute substantially to the gathering of experience with these techniques. The examples given, and problems or assignments to work out, should not necessarily be restricted to simplified or academic ones. This too can give a better insight into the usefulness of the analytical techniques (Milner, 1977). If the interactive system is well designed and much attention is given to the questioning, the system can be a device on which (several) students can work out their problems with minimal supervision. In this case " H E L P " facilities should be provided, where hints are given to the student how to proceed, or suggestions about what kind of mistakes have probably been made. At this point a warning should not be omitted. With an extensively equipped interactive system at his disposition, the student runs a risk of becoming a 'cookbook engineer' (Schmidtbauer, 1977) if improper use is made of the tool. He has to be taught how to check the usefulness and significance of the answers obtained. Computation should not be a substitute,

Most authors report the use of their package during the introductory courses for classroom demonstrations and a limited use by supervised students in this phase. In this period, familiarization with the analytical methods is generally the main goal. The aspect of design is reserved for continuation courses in the following years. Various types of assignments are reported where the design, using the interactive package, as well as implementation of the result of the design exercise are integrated. For graduates and post graduates a more independent unsupervised use of the package is intended.

the education

3.3. Experience with interactive systems Generally, the experience with interactive systems is limited to about five years for some early pioneers and shorter for others. At this moment, little quantitative and qualitative evaluation is available (Schmidtbauer, 1977: Gaines and Facey, 1975). A few authors give some comments, indicating a positive experience. Also students seem to have a positive appreciation of the facility they use (Schmidtbauer, 1977). Furthermore, specialists from other disciplines like pedagogy and didactics, seem seldom to be involved in the evaluation of the use of interactive systems. 3.4. Participation of students in the construction of the package Many institutes employ students for part of the construction of their software packages. From an educational point of view this seems to have mainly positive consequences. It mostly provides a high motivation for students when they know that regular use will be made of their products. Their functioning as part of a team induces a

Interactive computer programs for education and research: A survey sense of responsibility and teaches them how a complex problem may be decomposed into subproblems. Furthermore, during their project work they learn to use a complex computer system and they are taught how to document their products properly (Cellier and co-workers, 1977; Grepper and Djordjevic, 1977; Bruyn and Verbruggen, 1977). This part of the student's task should be very well supervised and there should be very clear and compulsory directives for the contents and the form of a program description (Cellier and co-workers, 1977). 4. DESIGN. C O N S T R U C T I O N AND C O N T E N T S

4.1. Design considerations The majority of the packages we looked into run on a dedicated minicomputer. This has consequences for the language in which they are programmed, which turned out to be FORTRAN IV in the majority of cases, sometimes supplemented by Assembler subroutines for special tasks (Cellier and co-workers, 1977; Grepper and Djordjevic, 1977; Barraud and Hanen, 1977; Bingulac and Farias, 1 9 7 7 ; Bruyn and Verbruggen, 1977: Van den Boom and Lemmens, 1977; Gray, 1977). Although it is noted (Barraud, 1977) that FORTRAN is a far from ideal language for this purpose, it is often used for reasons of portability. For the same reasons the 1/O-subroutines are made as device independent as possible (Shankar, Atherton and MacNeil, 1977). Many authors stress the modularity of their package as a means for attaining a flexible design, which allows easy updating and extension of the software as well as dividing the package into overlays to save memory space (Barraud and Hanen, 1977; Bingulac and Farias, 1977; Gray, 1977; Van den Bosch and Bruyn, 1977; Holt, 1975). Often subroutines are classified according to their purpose, e.g. I/O-modules, and update, compute and display subroutines (Van den Bosch and Bruyn, 1977). In the papers presented at the Barcelona symposium, no special interactive operating systems are described such as presented in Abel (1975). Although some systems are rather complex, they all run under a general purpose operating system, supplied by the computer manufacturer, or developed independently of the interactive application. In a number of cases (Gerber, Quenec'hdu and Thomas, 1977; Van den Boom and Lemmens, 1977) the interactive software has been constructed apart from the numerical application programs and functions as an extra level between operating system and application programs. It contains syntax checkers, graphics routines, data

115

transfer software, etc. One system exhibits parallel processing, but only on different processors (Grepper and Djordjevic, 1977) and a few have facilities for real-time data collection and control (Grepper and Djordjevic, 1977; Bruyn and Verbruggen, 1977). Most packages, however, operate upon simulated or pre-recorded data. 4.2. The management of the students In the previous section the students' role in the development has been discussed from an educational point of view. A negative aspect of this activity is that student's products tend to be less reliable than might be wished. This is due partly to lack of knowledge of possible error sources and operating conditions, and partly to lack of time or opportunity to test the software thoroughly for a wide variety of circumstances. Therefore, several institutes have adopted management schemes in which the parts provided are thoroughly checked and tested before they get the go-ahead for the software package. Especially the numerical stability and robustness of subprograms requires careful attention as it is very difficult afterwards to detect an error resulting from some special condition in which the subprogram is used and subsequently to trace an error source among the many parts of which a package may consist (Cellier and co-workers, 1977; Barraud and Hanen, 1977; Van den Bosch and Bruyn, 1977). 4.3. Contents of the packages In the Appendix we summarize different aspects of the packages which are described in the papers of the symposium. It turns out that most packages deal with classical control theory like Bode-plots, Nyquist diagrams and root-loci for linear single-input single-output systems. Apart from these basic techniques most packages have additional features like analysis of nonlinear systems (Cellier and co-workers, 1977; Shankar, Atherton and MacNeil, 1977; McCorkell, 1977), identification techniques (Gerber, Quenec'hdu and Thomas, 1977; Van den Boom and Lemmens, 1977; Gray, 1977; McCorkell, 1977; Wieslander, 1976a; Blessing, Bauer and Isermann, 1976; Clarke, 1974; K~lstr6m, Essebo and Astr6m, 1976), signal analysis techniques (Gerber, Quenec'hdu and Thomas, 1977; Van den Boom and Lemmens, 1977; Gray, 1977), optimal control (Gerber, Quenec'hdu and Thomas, 1977; Gray, 1977) etc. It seems that there is little exchange of experience with respect to the applicability and usefulness of different methods for calculation of basic techniques like root-locus or Nyquistdiagrams.

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W . J . M . LEMMENSand A. J. W. VAN DEN BOOM 5. I N T E R A C T I O N

Interactive systems should be designed with the potential user in mind. The conversation has to be shaped according to an implicit or explicit model of the kind of person with whom it will be conducted. As prospective users range from undergraduate students to researchers, this results in a wide variety of approaches, some of which offer a certain amount of flexibility to accommodate several categories of users (Gerber, Quenec'hdu and Thomas, 1977; Van den Boom and Lemmens, 1977). 5.1. What and how There are four kinds of information that an interactive system may need from a user: (a) A choice from a number of possibilities (e.g. which operation to perform or what kind of input signal to use). (b) A description of the structure of the system under study (the way in which a number of subsystems are linked). (c) Dimensions of (sub-) systems (order of transfer function, number of input signals to be added). (d) Numerical values of parameters. A specific package may not need all this information. Some special purpose programs only require data of type (c) and (d), other information being preprogrammed into the system. Information may be entered mainly by two means: (A) Using a pre-defined language in which commands may be given or data may be entered (Gerber, Quenec'hdu and Thomas, 1977; Grepper and Djordjevic, 1977; Bingulac and Farias, 1977; Thiga and Gough, 1977). There are even attempts to make the machine understnad natural language directives (Van den Boom and Lemmens, 1977). Statements in an interactive language may include information of type (b), (c) and (d) in the form of an expression that contains numerical values or symbolic representation of parameters or subsystems, whereas (a) type information is given in the form of mnemonics or special symbols. (B) Alternatively, the systems may be programmed to display a question and read an answer for every action to be performed and parameter to be used (McCorkell, 1977). In some cases such questions are bundled into a questionnaire and provided with default answers that are used if a user does not choose to change them. This seems a useful feature for demonstration of the use of a package or for questions that will mostly receive the same answer (Grepper and Djordjevic, 1977;

Van den Boom and Lemmens, 1977: Shankar, Atherton and MacNeil, 1977). A special form of question and answer interaction is the choice from some menu, that is displayed by the computer, whereby the answer is given either by using a light pen on a CRT-screen, or by typing some symbol on the keyboard. 5.2. Additional Jeatures For interactive systems error handling is a very important aspect. Unfortunately, most authors are very vague about this subject. No mention is made about how the syntax of the conversation is checked. The admissibility of numerical values is mostly checked in that part of the package in which they are used (Barraud and Hanen, 1977). Some packages contain a built in user's manual that may be consulted via the input-output medium (Gerber, Quenec'hdu and Thomas, 1977; Grepper and Djordjevic, 1977; Bingulac and Farias, 1977; Van den Boom and Lemmens, 1977). Others, especially those systems using some kind of programming language, obviously need an external manual. As for the output of results: most systems use some electronic display as the main output medium on which results may be presented in alphanumerical or graphical form. Some authors advocate a presentation that agrees as closely as possible with the presentation used in popular textbooks and lecture notes (Van den Boom and Lemmens, 1977; Shankar, Atherton and MacNeil, 1977), which requires a rather sophisticated graphics software. Others (Schmidtbauer, 1977) stick to a more simple form of output, bearing in mind future employment sites of students, where only time-sharing BASIC terminals are available. Not all packages we surveyed need direct interaction. One only consists of a set of subroutines that may be used in a student's program (Cellier and co-workers, 1977). Some systems, though they employ a direct conversation and immediate execution may also be used in an offline ('batch') mode (Gerber, Quenec'hdu and Thomas, 1977; Barraud and Hanen, 1977" Bingulac and Farias, 1977). In any case there is a command and data entry part and an execution part. Intervening into a running process is mostly not possible. Yet switching from one part of the package to another may often be done very quickly (Grepper and Djordjevic, 1977; Van den Boom and Lemmens, 1977; Gray, 19771. 6. H A R D W A R E

Most of the packages surveyed here run on a dedicated minicomputer which, in some cases, is coupled to one or more microcomputers used as

Interactive computer programs for education and research: A survey 'intelligent terminals' or data collectors (Grepper and Djordjevic, 1977). Real-time data gathering and control of physical processes may be realized using such microcomputers or special bus-lines and interfaces (Bruyn and Verbruggen, 1977). Larger mainframes offering time-sharing services are used also (Bingulac and Farias, 1977; Schmitbauer, 1977; Shankar, Atherton and MacNeil, 1977), but these are mostly not equipped to cope with real-time data. Some of the programs described run on a tabletop calculator (Aracil and Jimenez, 1977). Core requirements differ greatly between packages, but these should not be regarded as a measure of complexity because many systems make use of overlaying techniques or employ some form of dynamic memory allocation (Gerber, Quenec'hdu and Thomas, 1977). Generally speaking, 16k words of core is the minimum amount required for a package containing more than one special purpose program. Peripherals range from teletype terminals to colour video displays (Bruyn and Verbruggen, 1977), but mostly monocolour alphanumerical graphical display are used. Some packages also support plotters, paper tape punchers and other special purpose devices. 7. CONCLUSIONS

Due to the decreasing costs of the hardware, computers will be used more and more as standard equipment in educational institutes. In the next few years much experience with respect to the use of these machines in the educational environment will be gained. It may be hoped that this experience will be shared with others. Symposia and workshops are adequate means for such an exchange of information. As indicated before little evaluation has been done of the educational efficiency of interactive systems. Also specialists from other disciplines, such as pedagogy and didactics, are seldom involved in such an evaluation. Nevertheless evaluation of such a complex tool is important as it can give a better insight into the possibilities and dangers of interactive programs (Rosenbrock, 1977) and it can stimulate and guide their further development. REFERENCES Abel L.C. (1975). Structure and foundations of a large multitask CAD system. European Computing Conference, London 1975. In: Interactive Systems, Online. Allen A.J. and P. Atkinson (1974). The teaching of computer aided design of feedback control systems. Int. J. Math. Educ. Sci. Techn. no. 5, pp. 583-587. Allen A.J. and P. Atkinson (1975). An integrated suite of programs for the teaching of computer aided design of feedback control systems. Internal Report, Dpt. of Eng. and Cybern., University of Reading.

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Allen A.J. and P. Atkinson (1977). An integrated suite of programs for the teaching of computer-aided design of feedback control systems. I F A C Syrup. on Trends in Aut. Control Education, Barcelona, 1977. Aracil R. and A. Jimenez (1977). On the analysis and design of linear systems by means of a desk calculator. I F A C Syrup. on Trends in Aut. Control Education, Barcelona, 1977. Atkinson P. (1972). Computer aided design of closed loop control systems. Comput. Aided Des., 4(3), 120-128. Barraud A. and J. Hanen (1977). Design and development of mathematical software in automatic control. I F A C Syrup. on Trends in Aut. Control Education, Barcelona, 1977. Bingulac S.P. and J. Bassani (1976). Computer aided design of linear systems using L-A-S language. Colloquio FrancoBrasileiro, Rio de Janeiro, 1976. Bingulac S.P. and M.A. Farias (1977). Modern control theory education via L-A-S language. I F A C Syrup. on Trends in Aut. Control Education, Barcelona, 1977. Blessing P., U. Baur and R. Isermann (1976). Identification of multivariable systems with recursive correlation, least squares parameter estimation and use of a compensation technique. Paper CM-2, Fourth I F A C Congress on Identification and System Parameter Estimation, Tbilisi, USSR, 1976. Boom A.J.W. van den and W.J.M. Lemmens (1977). SATER, an interactive program package for education and research in parameter estimation-, control- and signal analysis techniques. I F A C Syrup. on Trends in Aut. Control Education, Barcelona, 1977. Bos A. van den (1976). Identification hardware and instrumentation. Identification and System Parameter Estimation, part 1, I V I F A C Syrup. on Identification and System Parameter Estimation, Tbilisi, USSR, 1976.

Bosch P.P.J. van den (1975a) TRIP, transformation and identification package for interactive computer aided control system design, Journal A, 16(3). Bosch P.P.J. van den (1975b). Transformation and identification package TRIP/ZIP (in Dutch). Report, Control Laboratory, EE. Dept. Technical University Delft, March 1975. Bosch P.P.J. van den and P.M. Bruyn (1977). The dedicated digital computer as a teaching tool in control engineering; interactive instruction and design, I F A C Syrup. on Trends in Aut. Control Education, Barcelona, 1977. Bosch P.P.J. van den and H.P.R. Schouten (1976). SIM An interactive simulation program for both continuous and concrete systems, Proc. 8th A I C A Congress, Delft, 1976. Bruyn P.M. and H.B. Verbruggen (1977). The dedicated digital computes as a teaching tool in control engineering; interactive in-line control, I F A C Symp. on Trends in Aut. Control Education, Barcelona, 1977. Cellier F.E., P.O, (3repper, D.F. Rufer and J. Toedtli (1977). Educational aspects of development and applications of a sub-program p~kage for control, I F A C Syrup. on Trends in Aut. Control Education, Barcelona, 1977. Clarke D.W. (1974). Identification package for a PDP-11 computer, QUEL Report no. 1113/74, Dpt. of Eng. Sc., Oxford University. Cs~.ki F., T. Ghl e.a. (1975). Procedure oriented program system for' contputer aided teaching of automatic control theory, Preprints Second IFIP World Conference on Computers in Education, p. 859, Marseille, France, 1975. Delaney D.G. (1975). CORMAT identification package users guide, University of Bradford. Elmqvist H. (1975). SIMMON, an interactive simulation program for nonlinear systems, Report 7502, Dpt. of Aut. Control, Lund Inst. of Techn. Gaines B.R. and P.V. Facey (1975). Some experience in interactive system development and application, Proc. IEEE,'63(6).

Gerber R., Y. Quenec'hdu and Y. Thomas (1977). Interactive systems as aids to teaching automatic control. I F A C Syrup. on Trends in Aut. Control Education, Barcelona, 1977. Gough N.E. and R.S.A. Thiga (1974). Application of CAIAD to computer-aided design of multivariable control systems, Report R 271, University of Bradford.

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LEMMENS a n d A, J. W. VAN DEN BOOM

Gough N.E. (1976a). Studies in computer aided design of control systems using CAIAD 1: Distillation column control, Report R 311, University of Bradford. Gough N.E. and D. Kleftouris (1976b). Studies in computer aided design of control systems using CAIAD, 2: Concentration control in experimental headbox, Report R 315, University of Bradford. Gough N.E., D.N. Kleftouris and R.S.A. Thiga (1977). Computer aided identification and multivariable control system design using convolution algebra, IFAC MVIN ConJerence Proceedings Canada, July 1977. Gray J.O. (1977). Interactive graphics design methods in the teaching of automatic control, IFAC Syrup. on Trends in Aut. Control Education, Barcelona, 1977. Gray J.O. and L.S. Savvides (1975a). The computer aided design of discrete data linear control systems, Report no. 192, Control Systems Centre, UMIST, 1975. Gray J.O. and L.S. Savvides (1975b). Interactive graphics using sinusoidal describing function methods, ISA Trans., 14(1). Grepper P.O. and M. Djordjevic (1977). A computer program for interactive control system design, IFAC Syrup. on Trends in Aut. Control Education, Barcelona, 1977. Grepper P.O. and M. Djordjevic (1976). POLOPS A computer program for interactive control system design, Proc. oJ'2nd M I M I Syrup., ZOrich, 1976. Holt R.C. (1975). Structure of computer programs: a survey, Proc. IEEE. 63(6). (lEE Conference on Computer Aided Control System Design, IEE Conference Publication Number 96. 1973). lsermann R. and P. Kneppo (1976a). Computer aided design of control algorithm for process computers. Regelungstechnik, 24(6), 181 216, 1976. lsermann R. and E. Dymchiz (1976b). A software package for process computer aided control system design. First I F A C / I F I P Syrup. on Computer Control, Talinn, USSR. 1976. K/ilstr6m C.G., F. Essebo and K.J. Astr6m (1976). A computer program for maximum likelihood identification of linear, multivariable stochastic systems. Paper 12.1, Fourth IFAC Congress on Identification and System Parameter Estimation, Tbilisi, USSR, 1976. McCorkell C. (1977). Computer aided dynamical system analysis and control for undergraduates, IFAC Symp. on Trends m Aut. Control Education, Barcelona, 1977. Melsa J.L. and S.K. Jones (1970). Computer Programs Jot Computational Assistance in the Study ~] linear Systems. McGraw Hill. Milner S.D. and A.M. Wilberger (19771. Determining approp-

riate uses of computers in education, Comput. Educt, iott, I, 117 123. Munro N. and J. Bowland. The computer aided control systems design suite. Control Systems Centre, UMIST. Munro N. and S. Rivkin (1972). Systems simulation program. Report no. 180, Control Systems Centre, UMIST, t972. Nievergelt J. (1975). Interactive systems for education The new look of CA1, Second IFIP World Conlerence ~,tl Computers in Education, Marseille 1975. Puente Alfaro, J.A. de la, M. Artes Gomes and P. Albertos Perez (1977). ECRA l; a course on classical control theory for continuing education, IFAC Syrup. on 7i'ends m Aut. Control Education, Barcelona, 1977. Ramani N. and D.P. Atherton (1976a). Manual for NLMVCON, System Dynamics and Control Lab., E.E. Dpt., Univ. of New Brunswick, Fredericton, N.B. 1976. Ramani N. and D.P. Atherton (1976b). Manual for STATEVARCON, System Dynamics and Control Lab., E.E. Dpt., Univ. of New Brunswick, Fredericton, N.B. 1976. Rosenbrock H.H. (1974). Computer Aided Control Systems Design. Academic Press, 1974. Rosenbrock H.H. 11977). The future of control, Automatica, 13, 387 392. Schmidtbauer B. (1977). Using general purpose computer terminal assignments in control education. IFAC Syrup. on Trends in Aut. Control Education, Barcelona, 1977. Shankar S. and D.P. Atherton (1976a). Manual for DFCON and MVCON, System Dynamics and Control Laboratory. E.E. Dpt., Univ. of New Brunswick, Fredericton, N.B. 1976. Shankar S. and D.P. Atherton (1976b). Manual for LINCON, System Dynamics and Control Lab., E.E. Dpt., Univ. of New Brunswick, Fredericton. N.B., 1976. Shankar A., D.P. Atherton and D.G. MacNeil (1977). Computer aided design of control using APL. IFAC Syrup. on Tremls in 4ut. Control Education, Barcelona, 1977. Thiga R.S.A. and N.E. Gough (1974). CAI.4D User'~ Guide, University of Bradford. Thiga R.S.A. and N.E. Gough (1977). An interactive language for computer aided identification and control systems design, Computer Aided Design, 9, no. 2. pp. 114 120. Wieslander J. (1976a). IDPAC, User's Guide, Ret:ision 1. Report 7605, Dpt. of Aut. Control, Lund Inst. of Techn, April 1976. Wieslander J. and I. Gustavsson (1976b). IDPAC An etficient interactive identification program. Paper 3.2, Fourth IFAC Congress on Identification and System Parameter Estimation, Tbilisi, USSR. 1976.

Conversation program for interactive control system design, 2 processors

Conversation mode

Multi-user, multivariable systems

INTOPS

PNE 1

PNE 2

Nyquist array, inverse Nyquist array, char. loc.

Nyquist, Bode, Nichols, Simulation. Identification, Strejc's method, Levy's method, pulse technique

Analysis and design for frequency, and time domain, signal analysis, estimation, parameter optimization.

Simulation

Various basic control, identification and signal analysis methods

Eigenvalues, vectors, controllability, observability, canonical form, Ricatti, Lyapunov, observer, state eq.

Structure of system can be drawn with lightpen

SIM

Multi-user, state space techniques

Transformation to different equivalent model descriptions, Menu interaction, lightpen

TRIP

Ricatti matrix-equation, Liapunov matrix equation, Controllability, observability, State transition matrix, Various identification and signal processing methods

PNE 6

High level interactive language

L-A-S

MIMO state description, nonlinear systems, quadratic optimisation, signal generation, FFT, correlation functions, non-linear programming, non-linear filtering, Max. Likelihood

Root-locus, Routh, Hurwitz

Multi-user, interactive system. No knowledge of computer science necessary. Runs on three different machines

SIRENA

Contents

PNE 3

Features

Name

APPENDIX: COMPARISON OF SOME INTERACTIVE COMPUTER PROGRAMS

B.Sc. Engineering Post Exp. Course

B.Sc. Engineering Post Exp. Course

Demonstrations lab. work student projects

idem

Demonstrations assignments lab. work undergraduates graduates

Graduates

Under test for education

Education

Ph.D. theses

idem

Design theses

Research in linear system theory

Under test

Research

1975

1976

1975

1976

1975

1971

Exp. since

McCorkell (1977)

Grepper et al. (1977) Grepper et al. (1976)

v. d. Bosch et al. (1976) v. d. Bosch et al. (1977) v. d. Bosch (1975a, 1975b)

Bingulac et al. (1976) Bingulac et al. (1977)

Gerber et al. (1977)

References

,.<

°.

Ca.

o

3

t~

t~

O

o

Features

Conversational mode, very fast and flexible data input routine with automatic scaling and alphanumeric labelling, window facility, runs on 7 machines

Flexible and fast operation possible between data entry change and display, modular form, runs on 7 machines

Interactive on-line Computer Graphics

Interactive on-line Computer Graphics

Question-reply interactive mode. Use of standard alphanumerical terminals

Minimum program knowledge required. Flexible set-up

Minimum program knowledge required. Flexible set-up

Minimum program knowledge required. Flexible set-up

Minimum program knowledge required. Flexible set-up

Minimum program knowledge required. Flexible set-up

Flexible set-up, question-reply with default answers, easily expandable

Name

SISO

MIMO

CADAL A

CADAL B

BODE STAB ROOT LAPLACE

L1NCON

DFCON

MVCON

NLMCON

STATEVARCON

SATER

Nyquist, root-locus, signal generation, simulation, stability, various identification methods

Canonical form for single and multivariable systems. Controllability, observability

Describing functions, analysis of multivariable systems

Analysis + design for linear and nonlinear systems. Multivariable systems

Describing functions, limit cycles, non-linear systems.

Basic graphical control, freq. resp., transient resp., root loci etc.

Solve standard time- and freq. domain problems

Similar facilities, root-locus. sampled data, char. loci, 2 input, 2 output

Frequency domain analysis, Nyquist, inverse Nyquist, freq. modulus and time domain simulation for linear continuous SISO systems

Continuous, discrete char. locus, time response, minimal realisation, non-linear techniques

Continuous, discrete, Nyquist, inverse Nyquist, Nichols, Bode, root-locus, time response and various other techniques, non-linear system analysis techniques

Contents

Delnonstrations assignments lab. work undergraduates graduates

Graduates

Assignments lab. work undergraduates graduates Assignments lab. work undergraduates graduates

Assignments

M.Sc sludellls

3rd year undergrad.

Demonstration lab. assignments undergraduates graduates

Demonstrations assignments lab. work undergraduates graduates

Demonstrations assignments lab. work undergraduates graduates

Education

M.Sc. theses

Multivariable systems design

Studies of non-linear multivariable systems

M ultivariable system studies

Stability studies

Used with other programs

Design of practical control system

Design of practical control system

Different projects industrial engineers

Different projects induslrial engineers

Research

1976

1974

1976

1976

1976

1976

1976

1975

1974

1974

1971

Exp. since

et al. et al. et al.

(1977) (1974) (1975)

11977~

Ramani el aI. 1976b)

Shanker et al. (1977) Shankar et al. (1976b) Ramani et al. !1976a)

Schmidtbauer ( 1977 )

Allen Allen Allen

Gray (1977) Munro and Bowland, Munro et al. (19721 Gray et aL (1975a) Gray et al. (1975b)

References

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r-

Combined identification and design

CAID

Procedure oriented analysis/synthesis

Identification package

Bode, Nyquist, Nichols, stability test, root locus, inverse Laplace, simulation, synthesis using several different performance indices

Interactive si mulation package for non-linear systems

SIMNON

CORMAT

Comand driven, simulation of continuous and discrete systems

Interactive identification package

IDPAC

Convolution algebra for analysis and design of M1MO systems in time domain

Correlation analysis, interactive model building

Least squares, maximum likelihood, correlation analysis, spectral analysis, Aikaike's test of order

CAD of control algorithms for SISO processes. Discrete PI, PID, PID2, deadbeat, state controller with observer. Digital simulation.

Interactive dialog, modular structure

CADCA

On line identification of SISO and 2 input, 2 output processes using different methods

Interactive package, small computer, short computation time

OLID

Industrial applications Industrial applications

General facility

Theses, application on industrial processes

Theses, application on industrial processes

Application on industrial processes laboratory work

Application on industrial processes laboratory work

General facility

Lab. work

Demonstrations assignments lab.work undergraduates graduates

Demonstrations assignments lab. work undergraduates graduates

Demonstrations

Demonstrations

1974

1975

1975

1975

1973

1975

Thiga (1974) Thiga (1977) Gough et al. (1977) Gough et al. (1974) Gough (1976a) Gough et al. (1976b)

Delaney (1975)

Cs~tki et al. (1975)

Wieslander (1976a) Wieslander et al. (1976b) K~ilstr6m et al. (1976) Elmqvist (1975)

Blessing et al. (1976) Isermann et al. (1976a) Isermann et al. (1976b)

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