http://www.ifac-papersonline.net/ en Copyright 05:33 PM Wednesday 19, 2013 IFAC-PapersOnline http://www.ifacpapersonline.com 05:33 PM Wednesday 19, 2013 05:33 PM Wednesday 19, 2013 ET webmaster@ifac-papersonline.net webmaster@ifac-papersonline.net http://www.ifac-papersonline.net/Detailed/30121.html 04:00 PM Wednesday 31, 1969 http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30122.html 04:00 PM Wednesday 31, 1969 http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30123.html 04:00 PM Wednesday 31, 1969 http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30124.html 04:00 PM Wednesday 31, 1969 In practical applications of sliding mode control, engineers may experience undesirable phenomenon of oscillations having finite frequency and amplitude, which is known as 'chattering'. At the first stage of sliding mode control theory development the chattering was the main obstacle for its implementation. Chattering is a harmful phenomenon because it leads to low control accuracy, high wear of moving mechanical parts, and high heat losses in power circuits. There are two reasons which can lead to chattering. • The chattering can be caused by fast dynamics which were neglected in the ideal model. These 'unmodeled' dynamics with small time constants are usually disregarded in models of servomechanisms, sensors and data processors. • The second reason of chattering is utilization of digital controllers with finite sampling rate, which causes so called 'discretization chatter'. Theoretically the ideal sliding mode implies infinite switching frequency. Since the control is constant within a sampling interval, switching frequency can not exceed that of sampling, which lead to chattering as well. Mechanism of chattering generating is demonstrated for control of inverted an pendulum with unmodeled actuator dynamics http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30125.html 04:00 PM Wednesday 31, 1969 Embedded controllers are essential in today electronic systems to assure that the behaviour of complex systems as cars, airplanes, trains, building security management systems, is compliant to strict safety constraints. I will review the evolution of embedded systems and the challenges that must be faced in their design. I will also present methodologies aimed at simplifying and speeding the design process. The role of hybrid systems in the development of embedded controllers will be outlined. Future applications such as wireless sensor networks in an industrial plant will also be presented. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30126.html 04:00 PM Wednesday 31, 1969 Necessary conditions for optimality have been established for hybrid systems. Unfortunately, these conditions lead to multi-point boundary value problems and they do not prevent from the combinatorial explosion when no constraints are given on the transitions. Different approaches have been proposed to approximate the solution, such as relaxed dynamic programming, non linear programming and sensitivity functions. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30127.html 04:00 PM Wednesday 31, 1969 This paper deals with the design of switching rules for switched linear systems with inputs, in such a way that the resulting closed-loop system is exponentially convergent. Two types of switching rules are addressed, that is state-based and observer-based rules. The developed theory is illustrated by two examples. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30128.html 04:00 PM Wednesday 31, 1969 In this paper we consider a class of discrete time piecewise-linear systems composed by linear discrete time LTI subsystems with autonomous switching. The aim is to propose a method for the synthesis of a hybrid observer. The approach proposed here consists on the combination of a discrete observer and a continuous observer. It is shown that under conditions related to minimum dwell time of each mode, one can express the switching law as a linear combination of the system input/output samples. The continuous observer is a piecewise-linear observer whose dynamics depend on the current active mode. Two estimation schemes are analyzed : on-line estimation and off-line estimation. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30129.html 04:00 PM Wednesday 31, 1969 In this paper, observers are synthesized for switched linear systems, resulting in switched observers including state jumps. The synthesis problem involves multiple Lyapunov functions and is formulated as a linear matrix inequality problem. It is assumed that the current mode (active dynamics) of the switched linear is unknown, and it will be shown that the estimate of the continuous states will be bounded at worst, if the mode is wrongly estimated. If the active dynamics is estimated correctly within a certain time, and the dwell time of the switched linear system is lower bounded, it will be shown that the bound of the estimation error can be reduced significantly. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30130.html 04:00 PM Wednesday 31, 1969 The analysis of error propagation in an Air Traffic Management (ATM) environment is addressed. The theory of Hybrid Systems is used to model the error evolution, an observability problem for a Markov Chain with discrete output symbols associated to the transitions is stated, and a runtime observer is proposed for estimating the probability of a given discrete state to be active. Sufficient conditions are given for characterizing the decidability of the addressed observability problem. The results are related to previous works on location observability of deterministic hybrid systems, and are used to analyze an ATM case study, the "clearance to change the flight plan". http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30131.html 04:00 PM Wednesday 31, 1969 A new low-and-high gain algorithm is presented for tracking control of timed continuous Petri Net (contPN) systems working under infinite servers semantics. The inherent properties of timed contPN determine that the control signals must be non-negative and upper bounded by functions of system states. In the proposed control approach, LQ theory is first utilized to design a low-gain controller such that the control signals satisfy the input constraints. Based on the low-gain controller, a high-gain term is further added to improve the system transient performance. In order to guarantee global tracking convergence and smoothness of control signals, in our work, a new mixed tracking trajectory (state step and ramp) is utilized instead of a pure step reference signal. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30132.html 04:00 PM Wednesday 31, 1969 This paper addresses a sampling problem for timed continuous Petri nets under infinite servers semantics. Different representations of the continuous Petri net system are given, the first two in terms of piecewise linear system and the third one, for the controlled continuous Petri nets systems, in terms of a particular linear constrained system with null dynamic matrix. The last one is used to obtain the discrete-time representation. An upper bound on sample period is given in order to preserve important information of timed continuous nets, in particular the positiveness of the markings. The reachability space of the sampled system in relation to autonomous continuous Petri nets is also studied. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30133.html 04:00 PM Wednesday 31, 1969 A Distributed Manufacturing System (DMS) is a collection of independent companies possessing complementary skills and integrated with transportation and storage systems. This paper proposes a new model for DMS employing first order hybrid Petri nets, i.e., Petri nets based on first order fluid approximation. More precisely, transporters and manufacturers are described by continuous transitions, buffers are continuous places and products are represented by continuous flows routing from manufacturers, buffers and transporters. Moreover, discrete events occurring stochastically in the system are considered to take into account the start of the retailer requests and the blocking of transports and raw material supply. With the aim of showing the model effectiveness, a DMS example is modelled and simulated under two different operative conditions. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30134.html 04:00 PM Wednesday 31, 1969 The purpose of this paper is to present a simulation model for Railway Stations (RS). Firstly, through a systemic description, we have shown that a RS can be considered as a Hybrid Dynamical System (HDS). Then, in order to represent the main intrinsic characteristics of RS, we have built a hybrid Petri net-based model. This model has been analyzed for i) checking purposes, and ii) evaluating some qualitative properties of the system. Finally, for illustrating the suggested methodology of study, a typical subway station has been simulated through a rush period scenario. Owing to a quantitative analysis of the marking evolution of the hybrid model, it is possible to make a performance evaluation of the station facilities and to underline some structural and functional limits of the studied station. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30135.html 04:00 PM Wednesday 31, 1969 We analyze a control strategy for the pick-and-place module of a component mounting device. We use a combination of techniques from bondgraphtheory, systems theory, process algebra and differential algebra to achieve this, and we show how the hybrid process algebra HyPA aides us in combining these techniques and in using them on a common hybrid model of the device. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30136.html 04:00 PM Wednesday 31, 1969 This paper presents a modeling and analysis strategy of human skill based on stochastic switched dynamics. As a fundamental mathematical model, the Stochastic Switched ARX model (SS-ARX model) is introduced. Then the modeling and analysis strategy of human skill is proposed based on the stochastic switched impedance model which can be regarded as one of the SS-ARX model. Finally, the developed strategy is applied to peg-in-hole task which involves interesting dexterous human skill, and the effectiveness of the proposed strategy is discussed. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30137.html 04:00 PM Wednesday 31, 1969 Embedded systems and their corresponding hybrid models are pervasive in engineering applications, therefore, systematic mathematical analysis using these models has become an important research area. Our approach to hybrid modeling with Hybrid Bond Graphs allows for seamless integration of physical system principles with discrete computational structures, but simulating the hybrid behaviors can be difficult and computationally expensive. In this paper, we develop a methodology that transforms Hybrid Bond Graphs into computational block diagrams and incrementally modifies the block diagram when mode changes occur. This forms the basis for a computationally efficient hybrid simulation algorithm. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30138.html 04:00 PM Wednesday 31, 1969 In this paper we consider multi-inventory systems in presence of uncertain demand. We assume that i) demand is unknown but bounded in an assigned compact set and ii) the control inputs (controlled flows) are subject to assigned constraints. Given a long-term average demand, we select a nominal flow that feeds such a demand. In this context, we are interested in a control strategy that meets at each time all possible current demands and achieves the nominal flow in the average. We provide necessary and sufficient conditions for such a strategy to exist and we characterize the set of achievable flows. Such conditions are based on linear programming and thus they are constructive. In the special case of a static flow (i.e. a system with 0-capacity buffers) we show that the strategy must be affine. The dynamic problem can be solved by a linear-saturated control strategy (inspired by the previous one). We provide numerical analysis and illustrating examples. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30139.html 04:00 PM Wednesday 31, 1969 This paper proposes a centralized solution to the problem of formation reconfiguration and keeping for fleets of satellites in the presence of persistent disturbances and under input-saturation and formation accuracy constraints. Relative position and attitude dynamics are considered. For suitable initial conditions the proposed control scheme produces system evolutions that fulfill the coordination constraints at any time and satisfy desirable control performance. This is accomplished by using a bank of Command Governor units in a hybrid framework. An example is provided in order to exhibit the effectiveness of the technique. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30140.html 04:00 PM Wednesday 31, 1969 We investigate optimal control problems for a class of non-stationary hybrid systems with autonomous location transitions. Using the Lagrange approach and the technique of the reduced gradient, we derive necessary optimality conditions for the considered class of problems. These optimality conditions are closely related to a variant of the Hybrid Maximum Principle and can be used for constructive optimization algorithms. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30141.html 04:00 PM Wednesday 31, 1969 This paper concerns an optimal control problem defined on a class of switchedmode hybrid dynamical systems. Such systems change modes whenever the state intersects certain surfaces that are defined in the state space. These switching surfaces are parameterized by a finite dimensional vector called the switching parameter. The optimization problem we consider is to minimize a given cost-functional with respect to the switching parameter under the assumption that the initial state of the system is not completely known. Instead, we assume that the initial state can be anywhere in a given set. We will approach this problem by minimizing the worst possible cost over the given set of initial states using results from minimax optimization. The results are then applied in order to solve a navigation problem in mobile robotics. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30142.html 04:00 PM Wednesday 31, 1969 In this paper we report of a technique to design optimal feedback control laws for hybrid systems with autonomous (continuous) modes. Existing techniques design the optimal switching surfaces based on a singular sample evolution of the system; hence providing a solution dependent on the initial conditions. On the other hand, the optimal switching times can be found, providing an an open loop control to the system, but those also are dependent on the initial conditions. The technique presented relies on a variational approach, giving the derivative of the switching times with respect to the initial conditions, thus providing a tool to design programs/algorithms generating switching surfaces which are optimal for any possible execution of the system. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30143.html 04:00 PM Wednesday 31, 1969 Approximate simulation relations have recently been introduced as a powerful tool for the approximation of discrete and continuous systems. In this paper, we extend this notion to hybrid systems. Using the so-called simulation functions, we develop a computationally effective characterization of approximate simulation relations which can be used for hybrid systems approximation. An example of application in the context of safety verification is shown. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30144.html 04:00 PM Wednesday 31, 1969 In this paper, we focus on a particular subclass of hybrid systems, the class of linear switching systems. We propose hybrid state space decompositions, based on hybrid invariant subspaces, which reduce the computational effort required for checking the structural property of asymptotic stabilizability. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif http://www.ifac-papersonline.net/Detailed/30145.html 04:00 PM Wednesday 31, 1969 Reachability computation is the central problem arising in the verification of hybrid or continuous systems. One approach, among others, to compute an over approximation of the reachable space is to split the continuous state space and to abstract the continuous dynamics in each resulting cell by a linear differential inclusion for which the reachable space may be computed with polyhedra. A previous work proposed to use characteristics of the affine continuous dynamics to guide the polyhedral partition. This paper presents an extension of this approach to uncertain planar systems where one parameter of the model may take its value in a polytope. It is shown that the result for all values of the parameter may be deduced from the computation for a finite number of values. An algorithm that performs the reachability computation and determines the minimum number of values of the parameter required at each step is proposed and exemplified. http://www.ifac-papersonline.net/static/luna/images/ifac/icon-download.gif