Authors: Zhang, Guofeng, Chen, Xiang, Chen, Tongwen

Abstract: This paper first introduces the fractional-order hold transformation that, together with the generalized bilinear transformation recently proposed in Zhang et al. [2007], contains all commonly used discretization methods as special cases. In light of this, it further shows that at fast sampling, all the digital approximations of an analog controller are equivalent in the sense of $ell_p$ induced norm for $pin [1, infty]$ when the analog controller is stable or in the sense of some gap metric even when it is unstable.

Keywords: Digital implementation; Stability of hybrid systems; Time-varying systems

Identifier: 10.3182/20080706-5-KR-1001.02576

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Akbari, Ahmad, Lohmann, Boris, Salimbahrami, Behnam

Abstract: This paper concerns with the generalized L_2 estimation of the disturbance applied to a vehicle steer wheel. The study is specially useful for active vehicle suspensions utilizing wheelbase preview information. To design an estimator to perform satisfactorily for a wide range of road irregularities and to care for system structured (parametric) uncertainties, a generalized L_2 gain based scheme is proposed to design the estimator. The problem is formulated using LMI’s and to ensure desired transient dynamics for the system, some pole location constraints are considered. To evaluate the effectiveness of the proposed controller it is compared with a Kalman estimator designed under similar conditions. The results demonstrate effectiveness of the proposed estimator.

Keywords: Adaptive and robust control of automotive systems

Identifier: 10.3182/20080706-5-KR-1001.01822

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Li, Lin, Jia, Yingmin, Du, Junping, Yu, Fashan

Abstract: This paper is devoted to the problem of H-inf output feedback control for linear singular systems with state time-varying delay. The purpose is to design a non-singular dynamic output feedback controller to ensure that the closed-loop system is regular, impulse free and stable with a prescribed H-inf performance level. Using the linear matrix inequality (LMI) approach, a new delay-dependent stability criterion is obtained by introducing a free-weighting matrix when estimating the upper bound of the derivative of Lyapunov Functional. And the corresponding stability controller design algorithm is proposed. Finally, a numerical example is included to demonstrate the effectiveness of the proposed method.

Keywords: Descriptor systems

Identifier: 10.3182/20080706-5-KR-1001.00660

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Hladowski, Lukasz, Galkowski, Krzysztof, Cai, Zhonglun, Rogers, Eric, Freeman, Christopher Thomas, Lewin, Paul

Abstract: In this paper we use a 2D systems setting to develop new results on iterative learning control for linear plants. It is well known in the subject area that a trade-off exists between speed of convergence and transient response. Here we give new results in this area by designing the control scheme using a strong form of stability for repetitive processes/2D linear systems known as stability along the pass (or trial). The resulting design computations are in terms of Linear Matrix Inequalities (LMIs) and they are also experimentally validated on a gantry robot.

Keywords: Iterative learning control; Iterative modelling and control design

Identifier: 10.3182/20080706-5-KR-1001.00477

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Conway, Richard, Horowitz, Roberto

Abstract: This paper presents a new control synthesis approach for dual-stage track-following servo systems with multi-rate sensing and actuation. For these systems, the robust track-following problem can be formulated as a periodic time-varying guaranteed cost control problem. To reduce the conservatism of the guaranteed cost control framework, uncertainty scalings such as those used in the D-K iteration heuristic for µ-synthesis are introduced. Although this results in a non-convex optimization problem, it is shown that it lends itself to a methodology similar to D-K iteration. Using this methodology, a controller is designed for a set of hard disk drives which minimizes the worst-case l2 semi-norm performance of the system.

Keywords: Identification and control methods; Mechatronic systems

Identifier: 10.3182/20080706-5-KR-1001.00143

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Siahaan, Hardy B.

Abstract: This paper considers a computational approach to obtain a reduced order model for polynomial nonlinear systems. The approach is based on balancing generalized gramians of polynomial systems and truncating the systems based on the balanced generalized gramians. The approach utilizes sum of squares programming for its computational purposes.

Keywords: Nonlinear model reduction

Identifier: 10.3182/20080706-5-KR-1001.00555

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Shah, Gaurang, Volker, Marten, Sonntag, Christian, Engell, Sebastian

Abstract: In industrial practice, extensive simulations are performed in order to analyse the safety and the correct operation of controlled chemical processes. One aspect of verifying the safe operation is to prove that the states of the system stay within a safe region for a certain set of inputs or disturbances which is the main theme of this paper. Recently, a rigorous method for this type of verification problem has been proposed which makes use of Barrier Certificates for verifying whether an undesired set of states can be reached. If the system dynamics can be described in polynomial form, the safety of the system can be proven algorithmically. The determination of a barrier certificate is a sum-of-squares (SOS) problem which can further be transformed into a non-convex Bilinear Matrix Inequality (BMI) problem. This paper deals with proving the safety of a Continuously Stirred Tank Reactor (CSTR), a non-linear system, using barrier certificates. Uncertainties are represented by a bounded disturbance acting on the system. Safety is explicitly proven for a convex set of initial conditions and a non-convex unbounded unsafe set. Two situations are considered, the uncontrolled plant and the closed-loop system with a state-feedback controller. For the solution of the BMI problem, three different numerical approaches are compared. It turned out that solving the non-convex BMI problem directly is more efficient than solving it using the convex iterative approach.

Keywords: Analysis of reliability and safety; Process control applications; Design and control

Identifier: 10.3182/20080706-5-KR-1001.01175

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Moberg, Stig, Öhr, Jonas, Gunnarsson, Svante

Abstract: A benchmark problem for robust feedback control of a manipulator is presented. The system to be controlled is an uncertain nonlinear two link manipulator with elastic gear transmissions. The gear transmission is described by nonlinear friction and elasticity. The system is uncertain according to a parametric uncertainty description and due to uncertain disturbances affecting both the motors and the tool. The system should be controlled by a discrete-time controller that optimizes performance for given robustness requirements. The control problem concerns only disturbance rejection. The proposed model is validated by experiments on a real industrial manipulator.

Keywords: Robust control of nonlinear systems; Robust control applications; Robust controller synthesis

Identifier: 10.3182/20080706-5-KR-1001.00208

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Song, Bongsob, Chwa, Dongkyoung, Baek, Woonhyuk, Jang, Seyong, Song, Hoin, Kim, Soontae

Abstract: This paper presents development of a longitudinal controller for an autonomous All-Terrain Vehicle (ATV). The developed ATV is a Controller Area Network (CAN) based distributed control system including multiple processors. Before developing the longitudinal controller, it is shown that the worst case response time of messages via CAN is bounded by appropriate assignment of priorities to all messages. Then, a control model for longitudinal control of ATV is proposed and validated experimentally. Finally, the longitudinal controller for ATV, based on a nonlinear control technique so-called Dynamic Surface Control (DSC), is designed and validated via simulation whether it can compensate for the worst case time delay and packet loss resulting from CAN communications.

Keywords: Control technology in the automotive industry

Identifier: 10.3182/20080706-5-KR-1001.01607

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Mavelli, Gabriella, Palumbo, Pasquale

Abstract: The paper investigates the optimal control problem for a stochastic linear differential system, driven by a persistent disturbance generated by a nonlinear stochastic exogenous system. The assumption of incomplete information has been assumed, that is neither the state of the system, nor the state of the exosystem are directly measurable. The standard quadratic cost functional has been considered. The approach followed consists of applying the Carleman approximation scheme to the exosystem, which provides a stochastic bilinear system. Then, the optimal regulator is obtained (i.e. the solution to the minimum control problem among all the affine transformations of the measurements). Better performances of the regulator are expected using higher order system approximations.

Keywords: Stochastic control; Estimation and filtering; Nonlinear systems

Identifier: 10.3182/20080706-5-KR-1001.01355

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Felicio, Paulo, A.S.A., Lourtie, Pedro

Abstract: This document reports work on the application of a Multiple Controller Adaptive Control algorithm based on fictitious reference signals. The algorithm has to select a controller in a small set of candidate controllers. The work shows steps towards a good selection of a cost functional and an analysis, based on recent stability results, shows why a cost function that is usual in other control methods is not suitable. With appropriate cost functional and set of controllers, simulations show the method is able to control a time varying process in the presence of measurement noise and loop delay, even outside the design interval for the parameter variation.

Keywords: Switching stability and control; Adaptive control; Time-varying systems

Identifier: 10.3182/20080706-5-KR-1001.00819

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Dourado, Antonio

Abstract: The traditional control curricula organization is not adequate for the new generations of students. This paper proposes the challenge to change completely the sequence of traditional control subjects. Firstly it proposes to develop control as a branch of information processing sciences. Paradigms for information are proposed: integral-differential paradigm, data-paradigm, linguistic paradigm. The control curricula in undergraduate education should start by fuzzy control, exploiting heuristics, games, intuition, in order to stimulate the student’s interest for the area. Control may be faced as a branch of machine learning and controllers have learning capabilities that can be classified into a proposed hierarchical structure. One introductory course for systems and one for control are proposed with syllabus oriented by this view.

Keywords: Control education

Identifier: 10.3182/20080706-5-KR-1001.01749

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Castaños, Fernando, Jayawardhana, Bayu, Ortega, Romeo, Garcia-Canseco, Eloisa

Abstract: In this note we identify graph-theoretic conditions which allow to write an RLC circuit as port-Hamiltonian with constant input matrices. We show that under additional monotonicity conditions of the network’s components, the circuit enjoys the property of relative passivity, an extended notion of classical passivity. The property of relative passivity is then used to build simple, yet robust and globally stable, Proportional plus Integral controllers.

Keywords: Stability of NL systems; Regulation; Asymptotic stabilization

Identifier: 10.3182/20080706-5-KR-1001.01047

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Aphale, Sumeet, Bhikkaji, Bharath, Moheimani, S.O. Reza

Abstract: Piezoelectric stack-actuated parallel-kinematic nanopositioning platforms have their first resonant mode at relatively low frequencies and also suffer from nonlinearities such as hysteresis and creep, resulting in a typically low-grade positioning performance. Closed- loop control algorithms have shown the potential to eliminate these problems and achieve robust, repeatable nanopositioning. In this work, the performance of three commonly used damping controllers is compared based on their closed-loop noise characteristics. The best one is combined with an integrator to produce accurate raster scans of large areas while imparting substantial damping to the system and minimizing inherent nonlinearities. A scanning resolution of approximately 8nm, over a 100μm × 100μm area is achieved.

Keywords: Perception devices and positioning systems; Identification and control methods; Mechatronic systems

Identifier: 10.3182/20080706-5-KR-1001.01998

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Lee, Hyunjin, Bequette, B. Wayne

Abstract: Type 1 diabetes is characterized by a lack of insulin production from the pancreas, causing high blood glucose concentrations and requiring external insulin infusion to regulate blood glucose. A novel procedure of “human friendly” identification testing using multisine inputs is developed to estimate suitable models for use in an artificial pancreas. A human-friendly multisine input signal offers improved identifiability on the dynamics of insulin to glucose, not causing serious deviations from the normal glucose concentration and satisfying insulin delivery pump specifications within acceptable time periods. An integrated formulation of constrained MPC is considered in order to reduce risks of hypoglycemia and hyperglycemia. Furthermore, a set of meal detection and meal size estimation algorithms are developed to improve meal glucose disturbance rejection when incoming meals are unknown. Closed-loop performance is evaluated by simulation studies of a type 1 diabetic individual, illustrating the ability of the MPC-based artificial pancreas strategy to handle measured and unmeasured meals.

Keywords: Biomedical system modeling, simulation and visualization; Identification and validation; Pharmacokinetics and drug delivery

Identifier: 10.3182/20080706-5-KR-1001.00715

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Pico-Marco, Enric, Navarro, Jose Luis

Abstract: This article addresses the computation of invariant and stabilizing control laws for dual-substrate fed-batch fermentors. The design is based on two commonly used model structures. It will be shown how to derive partial state feedbacks, using only biomass and volume as measures, that keep the substrates at a desired concentration provided the model is good enough and does not change with time. In the paper an analysis of invariance and a study of global stability within the framework of partial stability is provided.

Keywords: Dynamics and control; Microbial technology

Identifier: 10.3182/20080706-5-KR-1001.01638

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Ramírez Estay, Héctor Miguel, Sbarbaro, Daniel G.

Abstract: The control of nonlinear non-minimum phase processes by using traditional geometric approaches has lead to the development of specific design methods, such as the statically equivalent output approach. On the other hand, alternative design methods based on physical models, energy and mass balances, and the concept of passivity have been applied to a wide range of electrical and electromechanical systems. However, their application to process control has been limited. In this work, a comparative analysis of both design control approaches is presented. A standard continuous stirred tank reactor example is used to illustrate the differences among the approaches and the performances attained in both cases.

Keywords: Nonlinear process control; Design and control; Process modeling and identification

Identifier: 10.3182/20080706-5-KR-1001.01855

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Csáji, Balázs Csanád, Monostori, Laszlo

Abstract: Theoretical study of complex systems receives more and more attention as most sciences broaden their perspectives. The paper first briefly overviews a few important complexity approaches, then it presents a triple-level model for describing and analyzing collaborating enterprises. The environment is treated as a stochastic process, the core topology of the collaboration is represented by a graph and, finally, the dynamic behavior of collaborating enterprises is modeled as a Complex Adaptive System (CAS). Complexity measures for the different sub-models are suggested, some complexity drivers are investigated and it is argued that the resulted model can be effectively analyzed by simulation.

Keywords: Collaborative networked organizations principles; Methodologies and tools for analysis of complexity; Multi-agent systems applied to industrial systems

Identifier: 10.3182/20080706-5-KR-1001.02342

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Guadri, Ahmed, Dangoumau, Nathalie, Craye, Etienne

Abstract: Control systems are required to satisfy increasingly severe safety and performance criteria (reliability, security· · · ) mainly in the case of large scale systems. Such systems have to be described with a multiple abstraction levels paradigms such as hybrid systems (implementing both discrete and continuous dynamics). We present and formalize a new strategy for the reconfiguration of a hybrid system that relies on the specification of a region-based component oriented model which is updated whenever the system dynamics are modified. The standard controller is modified when a fault is detected and identified by use of an objectives automaton : Failing standard controls are replaced by a new sequence of controls chosen from an input space. Finally, we illustrate this method in the case of a system of communicating tanks.

Keywords: Hybrid systems modeling and control

Identifier: 10.3182/20080706-5-KR-1001.01108

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Prempain, Emmanuel, Postlethwaite, Ian

Abstract: This paper presents a nonsmooth optimization technique for solving a special mu-synthesis control problem. Attention is focused on controller synthesis problems that involve real diagonal scalings. An academic example illustrates the synthesis algorithm and a comparison is made with the well-known DK-iteration algorithm. This paper shows that nonsmooth optimization synthesis can provide better solutions than the standard DK-iteration algorithm.

Keywords: Robust control; Non-smooth and discontinuous optimal control problems; Optimization based controller synthesis

Identifier: 10.3182/20080706-5-KR-1001.02572

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Fuwa, Katsuhiko, Narikiyo, Tatsuo, Kandoh, Hisashi

Abstract: In this paper, a synthesis method of new disturbance observer, which can cope with frequency variation, is proposed. The main idea is to synthesize the disturbance observer as a gain-scheduled controller. The proposed disturbance observer gives the same low sensitivity property for disturbances with frequency variation as the conventional disturbance observer does. As an application, we consider vibration suppression control system for a flexible beam with multiple vibration modes. By numerical simulations and experiments, the proposed control scheme is shown superior to the conventional disturbance observer with respect to vibration suppression as compared.

Keywords: Robust control applications; Linear systems; LMIs

Identifier: 10.3182/20080706-5-KR-1001.00454

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Graichen, Knut, Petit, Nicolas

Abstract: A well–known problem in indirect optimal control is to find a suitable initial guess for the adjoint states which is sufficiently close to the optimal solution. This paper presents a new homotopy approach to overcome this problem by deriving an auxiliary optimal control problem (OCP) for which the adjoint states are simply zero. A continuation method is employed to smoothly reach the original OCP. The auxiliary OCP can be derived with respect to any given initial trajectory of the system, for instance obtained by forward integration. The approach is applied to the space shuttle reentry problem, which represents a benchmark problem in optimal control due to its high numerical sensitivity with respect to the initial solution.

Keywords: Algorithms and software; Aerospace applications; Optimal control theory

Identifier: 10.3182/20080706-5-KR-1001.02424

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Kwon, Bo Kyu, Kwon, Wook Hyun

Abstract: In this paper, we propose a new fixed-lag smoother that estimates the fixed-delayed state for a continuous-time stochastic system. The estimation error variance of the proposed smoother is minimized under the constraint that the estimated state converges to the real state exactly in finite time after noises or uncertainties disappear. For numerical computing, the proposed smoother is represented in a differential form. In order to achieve the convergence in finite time, any additional processes such as batch processing and sampling data through discrete-time techniques are not required. A numerical example is presented to illustrate the finite time convergence of the proposed smoother in comparison with the asymptotic convergence of the conventional Kalman smoothers.

Keywords: Filtering and smoothing

Identifier: 10.3182/20080706-5-KR-1001.01277

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Gonzalez Berlanga, Saul Israel, Niel, Eric, Zouari, Belhassen, Blanquart, Jean-Paul

Abstract: We propose a methodology for modeling systems with different operating modes using Nested Petri Nets (NPNs) based on Valk’s approach, where each token can be also considered as one Petri Net. NPNs provide a powerful tool for concurrent modeling and introduce interesting properties such as synchronization at a hierarchical level. In order to manage operating modes of critical and complex systems these properties are used to define and link component behaviors to the global system, through synchronized transitions. In order to formally verify these properties, CTL formulae will be used, translated from a logical table of technical specifications. The formulae allow a formal validation of the model and an examination of its coherency when the system switches to a new operating mode, under the influence of exceptional events. This verification is possible namely by using logic programming tools for the simulation and model checking. It is illustrated through a case study concerning a satellite’s control unit.

Keywords: Discrete event systems modeling and control; Switched discrete and hybrid systems; Verification

Identifier: 10.3182/20080706-5-KR-1001.01107

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008

Authors: Hur, Sung-ho, Balderud, Jonas, Katebi, Reza

Abstract: This paper describes the development of a control and monitoring oriented model of a plastic film manufacturing process. The model is mainly derived from first-principles and has been implemented in the Matlab/Simulink dynamic simulation environment. The development of the model forms the first phase of a project that aims to develop a nonlinear sub-space based monitoring, fault detection and trouble shooting system for the film manufacturing process.

Keywords: Modeling of manufacturing operations; Manufacturing plant control

Identifier: 10.3182/20080706-5-KR-1001.01413

Conference: Proceedings of the 17th IFAC World Congress, 2008

Location: COEX, Korea, South

Start Date: Sun Jul 06 2008 - End Date: Fri Jul 11 2008