Control Synthesis for a Class of Hybrid Systems Subject to Configuration-Based Safety Constraints

We examine a class of hybrid systems which we call Composite Hybrid Machines (CHM's) that consists of the concurrent (and partially synchronized) operation of Elementary Hybrid Machines (EHM's). Legal behavior, specified by a set of illegal configurations that the CHM may not enter, is to be achieved by the concurrent operation of the CHM with a suitably designed legal controller. In the present paper we focus on the problem of synthesizing a legal controller, whenever such a controller exists. More specifically, we address the problem of synthesizing the minimally restrictive legal controller. A controller is minimally restrictive if, when composed to operate concurrently with another legal controller, it will never interfere with the operation of the other controller and, therefore, can be composed to operate concurrently with any other controller that may be designed to achieve liveness specifications or optimality requirements without the need to reinvestigate or reverify legality of the composite controller. We confine our attention to a special class of CHM's where system dynamics is rate-limited and legal guards are conjunctions or disjunctions of atomic formulas in the dynamic variables (of the type x less than or equal to x(sub 0), or x greater than or equal to x(sub 0)). We present an algorithm for synthesis of the minimally restrictive legal controller. We demonstrate our approach by synthesizing a minimally restrictive controller for a steam boiler (the verification of which recently received a great deal of attention)

A Formal and Tool-Equipped Approach for the Integration of State Diagrams and Formal Datatypes

International audienceSeparation of concerns or aspects is a way to deal with the increasing complexity of systems. The separate design of models for different aspects also promotes a better reusability level. However, an important issue is then to define means to integrate them into a global model. We present a formal and tool-equipped approach for the integration of dynamic models (behaviors expressed using state diagrams) and static models (formal data types) with the benefit to share advantages of both: graphical user-friendly models for behaviors, formal and abstract models for data types. Integration is achieved in a generic way so that it can deal with both different static specification languages (algebraic specifications, Z, B) and different dynamic specification semantic

A Steam-Boiler Control Specification with Statecharts and Z

This report presents a solution to the steam-boiler control problem (see Chapter AS, this book). The main idea is to integrate a mathematical specification technique with a well-known engineering technique for the specification of safety-critical control systems. Our starting point is the technology of statecharts, which is currently being adopted in industry for the specification of embedded systems. To cope with the growing complexity and the safety requirements of these systems, we propose a combination of the specification language Z and statecharts, Z being used to model the data structures and data transformations within the system [9]. The next section sketches some key ideas relating to this combination. In the subsequent sections, we present key elements of a solution to the steam-boiler control specification problem. Throughout the presentation, we attempt to adhere closely to the original specification of the problem (see Chapter AS, this book), especially with respect to the physical interface of the control software. The full specification can be found in an Appendix (see CD-ROM Annex BW). 2 Specification Methodolog