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183
Observability and Controllability of Piecewise Affine and Hybrid Systems
 IEEE Transactions on Automatic Control
, 1999
"... In this pap e we prove in a constructive way, the ee ale b e we e pie a#ne syste and a broad class of hybridsyste de e d by inte line dynamics, automata, and propositional logic. By focusing our inveon the forme class, we show through countethat obse ability and controllability prope rtie cannot b ..."
Abstract

Cited by 93 (14 self)
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In this pap e we prove in a constructive way, the ee ale b e we e pie a#ne syste and a broad class of hybridsyste de e d by inte line dynamics, automata, and propositional logic. By focusing our inveon the forme class, we show through countethat obse ability and controllability prope rtie cannot be e asilydely from those of the comp tline subsyste Inste we propose practical nume te base onmixe te line programming. Keywords Hybrid syste controllability,obse ability, pie line syste pie a#ne syste mixe teline programming I. Introducti In recent yearsb oth control and computer science haveb een attractedb y hybridsystem [1], [2], [23], [25], [26],b ecause they provide a unified framework fordescribgARB( cesses evolving accordingto continuous dynamics, discrete dynamics, and logic rules. The interest is mainly motivatedb y the large variety of practical situations, for instance realtime systems, where physical processes interact with digital controllers. Several modelingformalisms h...
Equivalence of hybrid dynamical models
 AUTOMATICA
, 2001
"... This paper establishes equivalences among five classes of hybrid systems: mixed logical dynamical (MLD) systems, linear complementarity (LC) systems, extended linear complementarity (ELC) systems, piecewise affine (PWA) systems, and maxminplusscaling (MMPS) systems. Some of the equivalences are es ..."
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Cited by 71 (24 self)
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This paper establishes equivalences among five classes of hybrid systems: mixed logical dynamical (MLD) systems, linear complementarity (LC) systems, extended linear complementarity (ELC) systems, piecewise affine (PWA) systems, and maxminplusscaling (MMPS) systems. Some of the equivalences are established under (rather mild) additional assumptions. These results are of paramount importance for transferring theoretical properties and tools from one class to another, with the consequence that for the study of a particular hybrid system that belongs to any of these classes, one can choose the most convenient hybrid modeling framework.
A Clustering Technique for the Identification of Piecewise Affine Systems
, 2001
"... We propose a new technique for the identification of discretetime hybrid systems in the PieceWise Affine (PWA) form. This problem can be formulated as the reconstruction of a possibly discontinuous PWA map with a multidimensional domain. In order to achieve our goal, we provide an algorithm that ..."
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Cited by 49 (7 self)
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We propose a new technique for the identification of discretetime hybrid systems in the PieceWise Affine (PWA) form. This problem can be formulated as the reconstruction of a possibly discontinuous PWA map with a multidimensional domain. In order to achieve our goal, we provide an algorithm that exploits the combined use of clustering, linear identification, and pattern recognition techniques. This allows to identify both the affine submodels and the polyhedral partition of the domain on which each submodel is valid avoiding gridding procedures. Moreover, the clustering step (used for classifying the datapoints) is performed in a suitably defined feature space which allows also to reconstruct different submodels that share the same coefficients but are defined on different regions. Measures of confidence on the samples are introduced and exploited in order to improve the performance of both the clustering and the final linear regression procedure.
Towards a geometric theory of hybrid systems
 In HSCC’00, number 1790 in LNCS
, 2000
"... Abstract. We propose a framework for a geometric theory of hybrid systems. Given a deterministic, nonblocking hybrid system, we introduce the notion of its hybrifold with the associated hybrid flow on it. This enables us to study hybrid systems from a global geometric perspective as (generally non ..."
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Cited by 36 (15 self)
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Abstract. We propose a framework for a geometric theory of hybrid systems. Given a deterministic, nonblocking hybrid system, we introduce the notion of its hybrifold with the associated hybrid flow on it. This enables us to study hybrid systems from a global geometric perspective as (generally nonsmooth) dynamical systems. This point of view is adopted in studying the Zeno phenomenon. We show that it is due to nonsmoothness of the hybrid flow. We introduce the notion of topological equivalence of hybrid systems and locally classify isolated Zeno states in dimension two.
Verification of analog and mixedsignal circuits using hybrid systems techniques
 In FMCAD, LNCS
, 2004
"... Abstract. In this paper we demonstrate a potential extension of formal verification methodology in order to deal with timedomain properties of analog and mixedsignal circuits whose dynamic behavior is described by differential algebraic equations. To model and analyze such circuits under all possi ..."
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Cited by 33 (6 self)
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Abstract. In this paper we demonstrate a potential extension of formal verification methodology in order to deal with timedomain properties of analog and mixedsignal circuits whose dynamic behavior is described by differential algebraic equations. To model and analyze such circuits under all possible input signals and all values of parameters, we build upon two techniques developed in the context of hybrid (discretecontinuous) control systems. First, we extend our algorithm for approximating sets of reachable sets for densetime continuous systems to deal with differential algebraic equations (DAEs) and apply it to a biquad lowpass filter. To analyze more complex circuits, we resort to bounded horizon verification. We use optimal control techniques to check whether a ∆Σ modulator, modeled as a discretetime hybrid automaton, admits an input sequence of bounded length that drives it to saturation. 1
Stabilizing Model Predictive Control of Hybrid Systems
"... Abstract—In this note, we investigate the stability of hybrid systems in closedloop with model predictive controllers (MPC). A priori sufficient conditions for Lyapunov asymptotic stability and exponential stability are derived in the terminal cost and constraint set fashion, while allowing for dis ..."
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Cited by 29 (25 self)
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Abstract—In this note, we investigate the stability of hybrid systems in closedloop with model predictive controllers (MPC). A priori sufficient conditions for Lyapunov asymptotic stability and exponential stability are derived in the terminal cost and constraint set fashion, while allowing for discontinuous system dynamics and discontinuous MPC value functions. For constrained piecewise affine (PWA) systems as prediction models, we present novel techniques for computing a terminal cost and a terminal constraint set that satisfy the developed stabilization conditions. For quadratic MPC costs, these conditions translate into a linear matrix inequality while, for MPC costs based on 1,norms, they are obtained as norm inequalities. New ways for calculating low complexity piecewise polyhedral positively invariant sets for PWA systems are also presented. An example illustrates the developed theory. Index Terms—Hybrid systems, Lyapunov stability, model predictive control (MPC), piecewise affine systems. I.
OptimizationBased Verification and Stability Characterization of Piecewise Affine and Hybrid Systems
 In Hybrid Systems: Computation and Control
, 2000
"... In this paper, we formulate the problem of characterizing the stability of a piecewise affin (PWA) system as a verification problem. The basic idea is to take the whole R^n as the set of initial conditions, and check that all the trajectories go to the origin. More precisely, we test for semiglobal ..."
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Cited by 29 (8 self)
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In this paper, we formulate the problem of characterizing the stability of a piecewise affin (PWA) system as a verification problem. The basic idea is to take the whole R^n as the set of initial conditions, and check that all the trajectories go to the origin. More precisely, we test for semiglobal stability by restricting the set of initial conditions to an (arbitrarily large) bounded set X(0), and label as "asymptotically stable in T steps" the trajectories that enter an in variant set around the origin within a finite time T ,or as "unstable in T steps" the trajectories which enter a (very large) set X_inst . Subsets of X (0) leadin ton2W of the two previous cases are labeled as "nv classifiable in T steps". The domain of asymptotical stability in T steps is a subset of the domain of attraction ofan equilibrium poin t, an has the practicalmeanca of collectin inPv)v convW2xvP from which the settlin time of the system is smaller than T . In addition it can be computed algorithmically i...
Optimal controllers for hybrid systems: Stability and piecewise linear explicit form
 in Proceedings of the 39th IEEE Conference on Decision and Control
, 2000
"... In this paper we propose a procedure for synthesizing piecewise linear optimal controllers for hybrid systems and investigate conditions for closedloop stability. Hybrid systems are modeled in discretetime within the mixed logical dynamical (MLD) framework[8], or, equivalently [7], as piecewise af ..."
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Cited by 28 (7 self)
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In this paper we propose a procedure for synthesizing piecewise linear optimal controllers for hybrid systems and investigate conditions for closedloop stability. Hybrid systems are modeled in discretetime within the mixed logical dynamical (MLD) framework[8], or, equivalently [7], as piecewise affine (PWA) systems. A stabilizing controller is obtained by designing a model predictive controller (MPC), which is based on the minimization of a weighted 1/∞norm of the tracking error and the input trajectories over a finite horizon. The control law is obtained by solving a mixedinteger linear program (MILP) which depends on the current state. Although efficient branch and bound algorithms exist to solve MILPs, these are known to be NPhard problems, which may prevent their online solution if the samplingtime is too small for the available computation power. Rather than solving the MILP on line, in this paper we propose a different approach where all the computation is moved off line, by solving a multiparametric MILP (mpMILP). As the resulting control law is piecewise affine, online computation is drastically reduced to a simple linear function evaluation. An example of piecewise linear optimal control of the heat exchange system [16] shows the potential of the method.
Identification of piecewise affine systems via mixedinteger programming
 Automatica
, 2004
"... This paper addresses the problem of identification of hybrid dynamical systems, by focusing the attention on hinging hyperplanes (HHARX) and Wiener piecewise affine (WPWARX) autoregressive exogenous models. In particular, we provide algorithms based on mixedinteger linear or quadratic programming ..."
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Cited by 22 (4 self)
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This paper addresses the problem of identification of hybrid dynamical systems, by focusing the attention on hinging hyperplanes (HHARX) and Wiener piecewise affine (WPWARX) autoregressive exogenous models. In particular, we provide algorithms based on mixedinteger linear or quadratic programming which are guaranteed to converge to a global optimum. For the special case where switches occur only seldom in the estimation data, we also suggest a way of trading off between optimality and complexity by using a change detection approach. 1
Control of PiecewiseLinear Hybrid Systems on Simplices and Rectangles
, 2001
"... A necessary and sucient condition for the reachability of a piecewiselinear hybrid system is formulated in terms of reachability of a nitestate discreteevent system and of a nite family of ane systems on a polyhedral set. As a subproblem, the reachability of an ane system on a polytope is c ..."
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Cited by 18 (2 self)
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A necessary and sucient condition for the reachability of a piecewiselinear hybrid system is formulated in terms of reachability of a nitestate discreteevent system and of a nite family of ane systems on a polyhedral set. As a subproblem, the reachability of an ane system on a polytope is considered, with the control objective of reaching a particular facet of the polytope. If the polytope is a simplex, necessary and sucient conditions for the solvability of this problem by ane state feedback are described. If the polytope is a multidimensional rectangle, then a solution is obtained using continuous piecewiseane state feedback.