Alongkrit Chutinan

Computing Approximating Automata for a Class of Hybrid Systems

This paper presents a new algorithm for generating finite-state automata models of hybrid systems in which the continuous-state dynamics can be switched when the continuous-state trajectory generates threshold events. The automata state transitions correspond to threshold events and the automata states correspond to portions of the threshold surfaces in the continuous state space. The hybrid system dynamics are approximated by the automata models in the sense that the languages of threshold event sequences generated by the automata contain the threshold event language for the hybrid system. Properties of the algorithm for constructing and refining the approximating automata are demonstrated and the application of approximating automata for system verification is illustrated for a switching controller for an inverted pendulum. Relationships to other approaches to hybrid system synthesis and verification are also discussed.

Graphical Modeling of Hybrid Dynamics with Simulink and Stateflow

Simulink and Stateflow are tools for Model-Based Design that support a variety of mechanisms for modeling hybrid dynamics. Each of these tools has different strengths. In this paper, a new modeling construct is presented that combines these strengths to enable graphical modeling of hybrid dynamics within a single Stateflow chart. A new type of Stateflow state that acts as a Simulink subsystem is developed to facilitate graphical modeling of continuous dynamics using Simulink blocks inside Stateflow. Remote textual and graphical state access using new state-accessor blocks enables continuous states to be used in transition guards and reset actions. Key features of this new formalism are illustrated using various examples with hybrid dynamics.

ACTL strong negation and its application to hybrid systems verification

Abstract Model checking procedures for verifying properties of hybrid dynamic systems are based on the construction of finite-state abstractions. If the property is not satisfied by the abstraction, the verification is inconclusive and the abstraction needs to be refined so that a less conservative model can be checked. If the hybrid system does not satisfy the property, this verify–refine procedure usually will not terminate. This paper introduces the concept of strong negation for ACTL formulas as an auxiliary condition that can be verified to obtain a conclusive negative verification result from a finite-state abstraction in certain cases. The concepts are illustrated with an example from automotive powertrain control.

ACTL strong negation and its application to hybrid system verification

Abstract Model checking procedures for verifying properties of hybrid dynamic systems are based on the construction of finite-state abstractions. If the property is not satisfied by the abstraction, the verification is inconclusive and the abstraction needs to be refined so that a less conservative model can be checked. If the hybrid system does not satisfy the property, this verify-refine procedure will usually not terminate. This paper introduces the concept of strong negation for ACTL as an auxiliary condition that can be verified to obtain a conclusive negative verification result from a finite-state abstraction in certain cases. A method for identifying a sufficient set of states to be refined when the verification is inconclusive is also presented. The concepts are illustrated with an example.