Authors: I. Michael Ross; Fari ba Fahroo

Abstract: We present a class of efficient direct methods for solving nonsmooth dynamic optimization problems where the dynamics are governed by controlled differential inclusions. Our methods are based on pseudospectral approximations of the differential constraints that are assumed to be given in the form of controlled differential inclusions including the usual vector field and differential-algebraic forms. Discontinuities in states, controls, cost functional, dynamic constraints and various other mappings associated with the generalized Bolza problem are allowed by the concept of pseudospectral knots which we introduce in this paper. The computational optimal control problem is reduced to a structured sparse nonlinear programming problem. A simple but illustrative moon-landing problem demonstrates our method.

Keywords: optimal control,discontinuities,discretization,nonlinear programming

Identifier: 10.3182/20020721-6-ES-1901.00329

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Joaquin Alvarez; Iouri Orlov; Roque Martinez

Abstract: A nonsmooth controller design procedure for the regulation of a class of m- DOF mechanical manipulators with viscous and Coulomb friction is presented. Based on an invariance principle developed elsewhere, a discontinuous controller that uses only position measurement feedback is proposed. It is proved that the origin of the closed-loop system is globally and asymptotically stable. A discontinuous observer is also proposed to estimate the velocity and improve the performance of the controlled system. This kind of nonsmooth observer is important to achieve the global asymptotic stability of the closed-loop system. It is shown that the combination controller-observer can tolerate uncertainty in the friction coefficients if a bound on these parameters is known.

Keywords: discontinuous control,sliding mode,observers,robotic manipulators,Coulomb friction

Identifier: 10.3182/20020721-6-ES-1901.00838

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Qing-Long Han; Xinghuo Yu

Abstract: This paper considers the stability problem of linear delay-differential systems of neutral type. A discretized Lyapunov functional approach is developed. The resulting stability criteria are formulated in the form of a linear matrix inequality. For nominal systems, the analytical results can be approached with fine discretization. For uncertain systems, the new approach is much less conservative. Numerical examples show significant improvement over approaches in the literature.

Keywords: stability,time-delay,neutral type,uncertainty,linear matrix inequality

Identifier: 10.3182/20020721-6-ES-1901.00191

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Yoshifumi Okuyama; Fumiaki Takemori

Abstract: The physical parameters of controlled systems (plants) are uncertain and are accompanied by nonlinearity. The state space equation and the characteristic polynomial of the control system should, therefore, be expressed by an interval set of parameters. This paper examines the robust performance evaluation of that type of control system based on the existing area of characteristic roots (i.e., eigenvalues). In particular, in this paper, a sufficient condition for the roots area which is enclosed by a specified circle on a complex variable plane is given by applying the classic Sturm's theorem (division algorithm) to the four corners of a segment polynomial. The result that is obtained by finite calculations in regard to the coefficients of the segment polynomial, can be extended to general interval polynomials with multiple uncertain parameters.

Keywords: robust performance,uncertain polynomials,characteristic roots,Sturm's theorem,edge theorem

Identifier: 10.3182/20020721-6-ES-1901.00390

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Jukka Lieslehto; Mikko Hakala; Tero Karppinen

Abstract: The paper describes web-based distance learning material for a course in modelling and simulation. The course covers topics like systems and models, physical modelling, system identification, and simulation. An essential part of the material are interactive demos that are implemented with Matlab, Simulink and Matlab Web Server.

Keywords: education,identification,modelling,simulation,teaching

Identifier: 10.3182/20020721-6-ES-1901.01437

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Piotr Suchomski

Abstract: The paper deals with a problem of numerical conditioning of basic J - lossless factori-sations associated with suboptimal H∞-norm estimation of discrete-time processes described in the so-called delta-domain. State space formulae for dual J-lossless factorisations of a chain scattering representation of the estimated process are given. Solutions are obtained via solving two coupled algebraic Riccati equations. A relative condition number of the delta-domain algebraic Riccati equation is employed as a measure of numerical conditioning of these solutions. A numerical example is given to show that solutions obtained for the delta operator are much better-conditioned than its counterpart versions based on the common forward shift operator.

Keywords: estimation algorithms,linear filters,numerical algorithms,optimal estimation,Riccati equations

Identifier: 10.3182/20020721-6-ES-1901.00911

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Luca Consolini; Aurelio Piazzi; Mario Tosques

Abstract: This paper focuses on a special path following task arising from the needs of vision-based autonomous guidance: a given front point of a car-like vehicle that is within the look-ahead range of a stereo vision system, must follow a prespecified Cartesian path. Solution to this path following problem is provided by a new feedforward/feedback control strategy where the feedforward is determined by a dynamic generator based on exact dynamic inversion over the nominal vehicle model and the feedback is mainly issued by correcting terms proportional to the tangential and normal errors determined with respect to the vehicle's ideal trajectory. A convergence analysis of the resulting dynamic inversion based controller is established versus a vehicle's uncertain model defined via equation errors. A simulation example highlighting the controller's performances is included.

Keywords: autonomous vehicles,path following,dynamic inversion,nonlinear control systems,feedforward control,feedback control methods,robust performance

Identifier: 10.3182/20020721-6-ES-1901.00089

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: D. Escudero-Rodrigo; A. J. Sanchez-Salmeron

Abstract: An active vision system with two cameras has to be calibrated on-line to perform stereo vision applications. A calibration of a binocular system is possible using a small number of homologous features in both images. The correspondence problem can be resolved by using traditional template matching algorithms but it has a high computational cost. In this paper, some dynamic programming aspects are introduced to deal with template matching in order to reduce the execution time. Some experimental results demonstrate their viability and suggest other lines to improve its performance.

Keywords: search methods,image matching,dynamic programming,calibration,stereo vision

Identifier: 10.3182/20020721-6-ES-1901.01128

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: P. Belli; S. Bittanti; M. Carandente; A. De Marco; S. Piana

Abstract: Hot rolling mills suffer of severe torsional vibration in particular working condition (thin thickness). These vibrations are often explained as the result of an exogenous disturbance amplified by a resonance effect. Herein, another interpretation is supported, namely the true origin is to be found in the interaction between the kinematic chain and the plastic deformation of the strip in the roll bite. Thus, the vibrations are the result of an unstable limit cycle due to these interacting dynamics.

Keywords: steel industry,metals,torsional vibration,model,stability analysis

Identifier: 10.3182/20020721-6-ES-1901.01177

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: A. Cruz; V. F. Munoz; A. Garcia-Cerezo

Abstract: A significant advantage of multirobot simulation lays on the fact that their physical features and environment can be simulated, and hence, difficulties that spring when managing them are avoided. This paper shows a flexible method for simulating multirobot systems. It provides a simple and non proprietary structure of classes, that can be used as the backbone of complex developments, adapted to every multirobot system needings. The approach is based on discrete events systems, so it can simulate the inherent concurrency associated to multirobot systems. The paper presents results obtained when this solution is implemented using MATLAB, a numeric computation tool.

Keywords: autonomous mobile robots,discrete event systems,vehicle simulators,concurrency,trajectory planning

Identifier: 10.3182/20020721-6-ES-1901.00870

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Min Gu; Jean-Claude Piedboeuf

Abstract: A flexible robot arm with strain gauges distributed on it is used as a sensing unit in determination of endpoint position and force of flexible manipulator. The position and orientation of the flexible arm is expressed as a function of the local curvature. An interpolation technique gave a continuous curvature function from a finite set of measurements made with strain gauges. The endpoint force and moment depend not only on the local strains but also on the positions and orientations of the endpoint and those points where the strain gauges are located. Using the measured strains, one obtained the endpoint position and orientation as well as force and moment of the flexible arm. The experimental results demonstrated the effectiveness and accuracy of the proposed approach.

Keywords: flexible arm,endpoint,position,force,detection algorithms,tests

Identifier: 10.3182/20020721-6-ES-1901.00966

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: David H. Shim; H. Jin Kim; Shankar Sastry

Abstract: This paper presents a flight control system designed as on-board intelligence for rotorcraft-based unmanned aerial vehicles (RUAVs). This hierarchical flight control system, endowed with autonomy resembling sense-reason-act processes of intelligent agents in nature, gradually refines given abstract mission commands into real-time control signals for each vehicle. A tracking control layer is designed on the identified vehicle dynamics and integrated with a trajectory generator for logistical action planning. The proposed structure has been implemented on radio-controlled helicopters and validated in a variety of experiments. Results from way-point navigation, a probabilistic pursuit-evasion game and vision-based tracking of a moving target show the promising potential of intelligent flying robots.

Keywords: aircraft control,intelligent control,control system synthesis,predictive control,nonlinear systems,real-time systems,air traffic control

Identifier: 10.3182/20020721-6-ES-1901.01265

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Conrado Seibel; Jean-Marie Farines

Abstract: A formal approach for the mission planning and control of unmanned aircraft is described. Linear hybrid automata are used to model the chosen aircraft, the resources needed to perform a mission and the environment in which the aircraft will operate. This mission model can be verified with respect to safety criteria, like not running out of fuel, or used to perform parametric analysis, allowing the instantiation of symbolic parameters in flight plans for specific missions. Later, during mission execution, an on-board flight controller is used to control the progress of the mission by reacting to relevant external and internal events.

Keywords: autonomous vehicles,flight control,planning,automata

Identifier: 10.3182/20020721-6-ES-1901.01307

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: J. M. Perronne; C. Petitjean; L. Thiry; M. Hassenforder

Abstract: This paper describes how high-level of Object-Oriented concepts can be used to provide a generic, portable and polymorphic Fuzzy Logic framework. It highlights the way in which such OO concepts allow the extension of the programming language idioms with the semantics of the fuzzy logic field. A progressive approach presents; in a first step Fuzzy Logic systems; then, relevant classes, design patterns and architectures are identified. The considered aspects cover the composite structure, the polymorphic behaviour and the building of a system of fuzzy expressions. Finally, an example illustrates how the framework can be used in a conventional design strategy.

Keywords: fuzzy systems,object modelling techniques,software engineering,computer-aided system design

Identifier: 10.3182/20020721-6-ES-1901.00682

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: H. W. Knobloch; C. Ebenbauer; F. Allgower

Abstract: We propose a framework for disturbance attenuation in case of nonlinear systems affine in a multivariable input. Roughly speaking, the underlying idea of our approach exploits the nature of nonlinear systems with a multivariable input. In particular, we extend the system under investigation by additional control possibilities, which were formed out by the so-called mixed Lie brackets. It is shown that this extension is reasonable and may allow to establish special dissipation inequalities by using a certain type of discontinuous feedback law. We illustrate this analysis technique by examples and suggest a synthesis framework for disturbance attenuation which fits very well into this concept.

Keywords: discontinuous feedback,nonlinear multivariable control,stabilization,disturbance attenuation,dissipation inequalities

Identifier: 10.3182/20020721-6-ES-1901.00231

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Tolga Eren; Peter N. Belhumeur; Brian D. O. Anderson; A. Stephen Morse

Abstract: In this paper, a framework for maintaining formations of large number of mobile autonomous vehicles based on rigidity is proposed. The aim of this paper is to explore strategies for maintaining formations with more limited communication/sensing requirements. An inductive construction method for provably rigid formations is proposed, and a method for optimum angle measures between vehicles is developed. The method scales with the number of vehicles and is flexible to support many rigid formation shapes.

Keywords: autonomous vehicles,coordination,geometric approaches,graphs,graph theory

Identifier: 10.3182/20020721-6-ES-1901.01308

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Changho Lee; Yoo-Sung Kim; Jaehyun Park

Abstract: According to the prosperity of Internet technologies, users can not only get the information from remote control systems but also give control commands to the remote control systems via the Internet anywhere anytime. However, traditional distributed control systems in which the standard middleware such as CORBA or DCOM is used have the several problems: the compatibility between CORBA and DCOM, the reachability over the security barrier, and the portability to the embedded control systems. In this paper, the drawbacks of the traditional CORBA-based distributed control systems are discussed first. Then a functional framework for the web-based distributed control systems is proposed where SOAP (Simple Object Access Protocol) represented by XML (eXtensible Markup Language) is used for flexibility and portability. Also a distributed control system is implemented as an experiment to show that the proposed framework is more flexible and scalable than the existing distributed systems with the standard RMI protocols such as CORBA or DCOM.

Keywords: distributed control system,CORBA,SOAP,XML,real-time control

Identifier: 10.3182/20020721-6-ES-1901.00943

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: W. H. Wang; K. D. Liu; D. H. Zhou; C. H. Wang

Abstract: This paper proposes a fuzzy and rough sets integrated approach to fault diagnosis. The basic concepts of the rough set theory are firstly introduced, and then it describes how the rough sets theory is combined with fuzzy logic to form a new fault diagnostic scheme. An application example, marine diesel engine fault detection and diagnosis system, is presented, and the simulation results with on board real data demonstrate the effectiveness of the proposed approach.

Keywords: fault detection,fault diagnosis,fuzzy sets,fuzzy logic,decision tables

Identifier: 10.3182/20020721-6-ES-1901.00772

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: A. Skaf; B. David; Z. Binder; B. Descotes-Genon

Abstract: The man-machine systems design is a major concern for the computer scientist, the control engineer and the ergonomicist. An adequate design for such systems means optimisation of their performance, which is the result of taking into account the human element since the design stage. Human integration, in the design stage, can strengthen the stability and optimality of all system functions. This paper deals with the problem of man-machine systems design by proposing a general approach based on system analysis methodology, action identification and action specification. All those aspects will be treated in this paper.

Keywords: man/machine interaction,socio-technical system,design,methodology,ergonomic,co-operation

Identifier: 10.3182/20020721-6-ES-1901.01616

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Ola Markusson; Haan Hjalmarsson; Mikael Norrlof

Abstract: In this contribution we place ILC in the realm of numerical optimization. This clarifies the role played by the design variables and how they affect e.g. convergence properties. We give a model based interpretation of these design variables and also a sufficient condition for convergence of ILC which is similar in spirit to the sufficient and necessary condition previously derived for linear systems. This condition shows that the desired performance has to be traded against modeling accuracy. Finally, one of the main benefits of ILC when non-minimum phase systems are concerned, the possibility of non-causal control, is given a comprehensive coverage.

Keywords: iterative methods,learning control,nonlinear systems,convergence analysis,non-minimum phase systems

Identifier: 10.3182/20020721-6-ES-1901.00226

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Dianhui Wang; Tharam Dillon

Abstract: This paper presents a generalized Markov stability criterion for linear systems by determining the Cauchy index in arbitrary segments. Based on the proposed result, several new algebraic criteria on Schur stability and strict aperiodicity for linear systems are obtained.

Keywords: linear control systems,stability criteria,Markov parameters

Identifier: 10.3182/20020721-6-ES-1901.00193

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Gregory Levitin; Jacob Rubinovitz; Boris Shnits

Abstract: Robotic assembly line balancing (RALB) is specific for robotic assembly, where different robots require different assembly times to perform the same task because of their specialization. The problem includes optimal assignment of robots to line stations and balanced distribution of work between different stations. It aims at maximizing the production rate of the line. This problem is solved by a genetic algorithm (GA). Different procedures for adapting the GA to the RALB problem are introduced, including a local optimization (hill climbing) work-piece exchange procedure. The best combination of these procedures is reached by testing on a set of randomly generated problems.

Keywords: assembly lines,robots,productivity,genetic algorithms,hill climbing

Identifier: 10.3182/20020721-6-ES-1901.00016

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Tako F. Lootsma; Roozbeh Izadi-Zamanabadi; Henk Nijmeijer

Abstract: A geometric approach to FDI diagnosis for input-affine nonlinear systems is briefly described and applied to a ship propulsion benchmark. The analysis method is used to examine the possibility of detecting and isolating predefined faults in the system. The considered faults cover sensor, actuator, and parameter faults.

Keywords: geometric approach,input-affine nonlinear systems,fault detection,fault isolation,ship propulsion benchmark

Identifier: 10.3182/20020721-6-ES-1901.00769

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Eric C. Kerrigan; John Lygeros; Jan M. Maciejowski

Abstract: The problem of reachability computations for systems with simultaneous constraints on the states, control inputs and disturbances is treated. A problem formulation is provided for the general case and, for the special case where the disturbance constraints are independent of the states and inputs, it is discussed how the solution can be approached using standard geometric concepts. It is also discussed how the procedure can be implemented for a class of piecewise affine systems with polyhedral constraints using computational geometry software.

Keywords: nonlinear systems,uncertain dynamic systems,controllability,reachability,invariance,constraint satisfaction,piecewise linear,robust control

Identifier: 10.3182/20020721-6-ES-1901.01125

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002

Authors: Mehdi Rafizadeh; Ahmad Afshar; Hassan Gharghi

Abstract: To produce a certain polymer with desired properties, some of polymerization variables should be controlled. In this paper, a oil bath was designed and constructed for the heating and cooling of the reactor. Then, a mechanistic model was developed for the solution polymerization of methyl methacrylate in a batch reactor. This model is highly non-linear. A Globally Linearizing Control (GLC) strategy was applied to control the reactor temperature. A linear PI controller was designed to eliminate the error. The controller performance was viable and the previously developed GLC method is suitable for the oil heating system.

Keywords: chemical industry,feedback control,linear control systems,linearization,modeling

Identifier: 10.3182/20020721-6-ES-1901.01361

Conference: Proceedings of the 15th IFAC World Congress, 2002

Location: , Barcelona, Spain

Start Date: Sun Jul 21 2002 - End Date: Fri Jul 26 2002