Computer-aided Control System Design Research Articles

Object-Oriented Programming and the Implementation of a Block Diagram Editor for the Macintosh

Abstract A block diagram editor has been developed for the Macintosh personal computer from a specification developed for a general graphical human-computer interface for an extended X-based Control Engineering workstation (eXCeS). It was implemented using THINK C. a version of C with object-oriented extensions that has been specially developed to provide case of programming for graphics based applications in the Macintosh environment. Our experiences are reported on using this programming environment for this application and details are given of its design and implementation. We also comment on the applicability of the object oriented paradigm for the development of Computer-Aided Control Systems Design (CACSD) tools.

CAD of Discrete Multivariable Control Systems Using Singular Characteristic Patterns and Vectors

This paper introduces the concept of singular characteristic patterns of discrete multivariable control systems based on discrete convolution algebra. The implementation of these concepts in a new software language CBSL for simulation and computer-aided design of robust control systems is described and illustrated by the design of a robust control system for an unstable chemical reactor

Plant Models for Use with Computer-Aided Control System Analysis and Design Packages

A portfolio of plant models based upon real-world industrial plants and processes has been developed for use in control system analysis and design. The seven nonlinear models in this portfolio are Written In two widely-used simulatIon languages, ACSL and TSIM 2. A set of linear models has been extracted from the control literature and put in the form of Matlab and Ecstasy files. The nonlinear models are being formed into a model library that will be accessible over an academic data network in the United Kingdom

The Making of Exces - A Software Engineering Perspective

Abstract This paper is concerned with the software engineering aspects of the development of eXCeS (Extended X-based Control Engineering workStation) - an integrated computer-aided design environment for control engineering. The requirements of such an environment are analysed and major implementation issues including modularised infrastructure, standard ‘look and feel’ and uniform and extensible data environment are discussed. The eXCeS environment takes account of each of these issues in order to provide a user interface which meets the needs of control engineers, incorporates the latest developments in user interface technology and provides a platform for a wide spectrum of software products for computer-aided control system design.

A Second-Generation Expert System for Computer-Aided Control System Design

Abstract The CACE-III expert system for designing series lead-lag compensators for single-input/single-output plants to satisfy three frequency-response specifications has been implemented using the Gold Works inference engine and expert-system development tools. The implementation makes use of the frames and user-interface features of Gold Works to provide an environment from which further extensions of the design approach or other design methods can be created in an orderly fashion. The control-analysis program Matrix x has been used to perform the required control-system modeling and analysis calculations at the request of the expert system The tools that have been developed for handling the varied interactions between the expert system and the numerical applications program are described. Also, a number of ways in which the present design system can be improved and expanded are presented

Computer Integrated Instruction for/with a CACSD-Tool

Abstract CACSD-Tools (Computer-Aided Control System Design) are increasingly used for the design of control systems. Based on the well established control theory those tools offer a large number of complex functions for system design and simulation, ranging from graphical editing of block diagrams to system simulation and controller design. Two aspects of education and CACSD-Tools will be discussed in the paper. The first aspect is the introduction of a novice user to a CACSD-Tool. A Learning Environment (LE) will be presented. Its aim is to offer the user flexibility where and when to get an introduction to the tool and to support the user’s evolution from a novice to an expert user. Being integrated on the level of the user interface of a window-oriented workstation, the user can step through the learning material offered by the LE and use the tool simultaniously to applicate the learnt concepts in this tool environment. The paper will describe the general structure of the Learning Environment and the learning material for the CACSD-Tool MATRIXx as an example of application. The second aspect is the use of the LE and the CACSD-Tool for control theory education. Using the same concepts of an open learning environment an example of the integration of theory presentation and simulation with MATRIXx will be presented. The learning material is composed of lessons in theory, exercises with the tool and evaluation tests. MATRIXx is a registered trademark of Integrated Systems Inc, Santa Clara, CA, USA.

Knowledge-Based Interfaces to a Computer-aided Control System Design Package

Design of automatic control systems is a computationally intensive process. This motivates the development of accessible, easily usable and shareable interactive computing environment incorporating specialized knowledge of the theory and codified practice of automatic control. Expert and knowledge based systems play key role in creation of such environment. The expert system techniques can be used for the design of control systems. SFPACK is a special purpose interactive computer language for control system design. One feature of this package is that it incorporates an expert system development facility called DECESS. This expert system development facility can be used to design controllers for linear multivariable control systems. This paper describes an object-oriented knowledge interface to SFPACK. SFPACK has been used as a teachware for presenting techniques in control system design. The package runs on a SUN workstation or VAX machines and has been used successfully in a course on control engineering at the graduate level.

Computer-aided design and analysis of linear multivariable control systems using the systematic design approach

A new approach for the design of multivariable feedback control systems in the frequency domain is presented. The techniques handle stability, performance, and robustness aspects of the design problem satisfactorily. The overall approach is systematic and intuitively appealing. A new computer-aided control system design package called SFPACK is developed. This package has implemented the new frequency response design techniques. The package is interactive and command-driven, and it is used as a teaching tool for helping the students to understand the concepts of the design approach. The MAT-LAB-derived control environment in SFPACK is extended to provide the user with an expert system development environment.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Expert system for SROOT

The development of an expert system in the domain of computer-aided control systems design is presented. An expert system has been developed and incorporated into an existing control systems design package called SROOT. The combined software is used to design linear single variable systems using the root locus techniques. The expert system provides software-based design expertise involving control theory, visual aspects of graphical outputs and engineering heuristics. Two new components for the expert system are introduced. These are the two types of facts used and a firing order unit. The former enables rules to be written in a generally-applicable format. The latter provides a systematic way of applying expertise. An overall design heuristic which supports the design of lead/lag compensators for the systems considered is introduced. A design example is given to exhibit the capability of the expert system.

An Automated Control System-Designing System Assisted by Hypothetical Reasoning

Most studies of the so-called CACSD (Computer-Aided Control System Design) have aimed at the development of computer systems which will assist control engineers to design effectively, making better use of sophisticated machine interfaces and the graphic environment, and do not aim at automated control design beyond assisting the user in designing control systems. The present study has developed a system, which is aimed at the automation of classical control system design, by describing the dialogue between man and computer as a computer program through techniques of knowledge engineering. In particular, hypothetical reasoning systems supported by TMS (Truth Maintenance System) are used in order to automate trial and error procedures which are problems in classical design methods. In other words, a hierarchical system has been constructed where a control system-designing expert system based on hypothetical reasoning is placed at the meta-rule layer above the procedure and tool layers. This paper illustrates the basic structure of this expert system and the utilization forms of hypothetical reasoning in control system design, and shows the actual operation of the system as seen through a design example.

Management of Computer-Aided Control System Design from Concept to Flight Test

Active control technology (ACT) has brought a dramatic change to the way aircraft can be designed and flown. The challenge for flight control research is, given the potential of ACT, to define what is required. The problem is that to answer this question a 'flyable' implementation is needed, whether for a piloted flight simulator or for full-scale flight. The need for an implementation introduces issues of software design and management and a possible 'conflict' with the needs of research. This paper describes an environment for flight control law research being developed in Flight Management Department at RAE Bedford, to provide a rigorous yet flexible framework. A comprehensive life cycle is defined for the evolution of flight control laws from concept via piloted simulation to flight test. In its current fonm, the life cycle has four major phases: conceptual design, engineering design, flight clearance and flight test. Conceptual design covers off-line simulation - modelling, design anc dnalysis - and some pilot-in-the-loop simulation using RAE's Advanced Flight Simulator. The outputs from this stage include infonmation on the response types and system characteristics required. Engineering design is the process of full control law design and includes further refinement of control system architectures via modelling and more detailed piloted simulation. Flight clearance consolidates results from earlier stages and achieves a verified implementation for the target flight control computer. Flight test evaluates the control system in full scale flight and appropriate operational conditions, with further comprehensive data collection. A structured description of all these phases is presented, with emphasis on the conceptual phase; some examples of the control law life cycle are given with particular application to helicopter flight control. The verification and validation issues associated with the attendant software development are also addressed.

A man-machine interface for computer-aided design and simulation of control systems : Barker, H.A., Chen, M., Grant, P.W., Jobling, C.P., and Townsend, P.Automatica, 1989, 25.2, 311–316, 34 refs.

A man-machine interface for computer-aided design and simulation of control systems : Barker, H.A., Chen, M., Grant, P.W., Jobling, C.P., and Townsend, P.Automatica, 1989, 25.2, 311–316, 34 refs.

The Impact of Recent Developments in User-interface Specification, Design and Management on the Computer-aided Design of Control Systems

This paper describes the characteristics of advanced graphical user interfaces for the computer-aided design of control systems which can be developed using modem windowing environments. The significance of the emergence of windowing standards, such as the X Window System, and of user-interface standards, such as OPEN LOOK, is discussed. The increasing imponance of object-oriented programming for the development and maintenance of these sophisticated user interfaces is noted, and the need for an object-oriented database for the support of the design process is identified. Examples are given of the advantages for control system design of being able to deploy a number of graphical tools simultaneously in a multi-window environment

Solutions of the second benchmark control problem

A report is presented on the results of the second benchmark control problem prepared by the Benchmark Working Group of the IEEE Control Systems Society Technical Committee on computer-aided control system design (CACSD). The problem deals with a continuous-time missile autopilot design. The purpose of this benchmark is to provide a useful measure of some of the capabilities of computer-aided control system design packages. The problem requires time simulations, eigenvalue calculations, and frequency-response plots of relatively high-order linear systems. The problem is described, and the results submitted to date are summarized. >

Development of a new generation of interactive CACSD environments

A description is given of the development of a novel interactive computer-aided control system design (CACSD) package for the design of linear multivariable control systems. The package incorporates the stable factorization design technique and other recent design methodologies, such as the systematic design approach. To provide a high level of interactive design environment for the user, knowledge-based expert system development tools are provided within the package. In addition, the user is provided with the facilities to write user-defined functions and procedures.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Structural decomposition and new algebraic method for large-scale systems

The interconnections of subsystems are structurally decomposed and the stability of the overall large-scale system is then investigated, based on these decompositions. With these formulations, the decentralized control design for the interconnected subsystems can be treated as an algebraic problem. The architecture is then extended to solve the decentralized estimation and stabilization problem. The emphasis here is to propose a new method for the qualitative analysis and design of large-scale systems. The advantage lies in its feasibility for a computer-aided control system design (CACSD) set-up.

Teaching multivariable control with CADCS packages and PCs

A first multivariable control experiment is described for the teaching of control. The different processes which can be used in the experiment are simulated with inexpensive analog components. Computer aided control system design packages (CADCS) are used extensively to derive controllers for these multivariable processes. The designed controllers are initially simulated in closed-loop form using CADCS packages with interactive graphics, and then implemented on IBM PC compatibles to verify their effectiveness in the control of the analog processes. Important phenomena such as multivariable interaction, actuator and process saturation, limit cycling, and reachability are brought out as the students are conducted through the process of controller design and evaluation. Experimental results are given from a typical teaching laboratory exercise on one of the processes.

Transputer arrays and computer-aided control system design

The design of a hardware accelerator for supporting CACSD computations is considered in relation to H∞ design. The key algorithms are identified and parallel solutions formulated. The speedup of these techniques is then assessed with respect to trial implementations on a network of transputers.

An efficient representation for linear constraints

An efficient representation for the linear constraints generated by a recent CACSD (computer-aided control system design) method has been developed. The linear constraints arise from engineering constraints on the time- and frequency-domain responses of the closed-loop system. The representation reduces the storage requirements and improves the efficiency of the quadratic programming algorithm used by the design method. The algorithm performs two distinct operations on the individual constraints. The first determines if a constraint has been satisfied and the second is the computation of the distance in a specified search direction. >

Computer-aided design and analysis for a class of nonlinear systems

A description is given of a computer-aided control system design package, NLCON, that supports analysis and design functions for single-input/single-output nonlinear control systems with a single nonlinearity. The single nonlinearity can be one of seven nonlinearities commonly encountered in mechanical systems, and its location within the system is not restricted. The controller design benefits from designer experience, but it is facilitated by the software package, since program operation is highly interactive and the interface is user friendly. The analysis functions supported include sinusoidal-input describing functions and limit-cycle analysis, frequency-response determination, and jump-resonance analysis. Design functions include procedures for compensator modification to modify limit-cycle and jump-resonance behavior. A design advisory is provided for some simple design situations. Examples to illustrate various facets of program operation are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>