Symbolic Algebraic Discrete Systems : Applied to the JAS 39 Fighter Aircraft
Roger Germundsson, Johan Gunnarsson, Jonas Plantin · 1995
In this document we present symbolic algebraic modeling and analysis techniques applied to the landing gear subsystem in the new Swedish fighter aircraft, JAS 39 Gripen. This is a work in progress report within the larger project COmplex Hybrid SYstems (COHSY) which is a joint project between several academic (Mechanical Engineering, Computer Science and Electrical Engineering) and industrial (Saab Aircraft, Volvo Aero and VOAC) partners. It is also part of a long term effort within the Automatic Control group in Linköping to deal with discrete dynamic systems, mainly for control applications. Our methods are based on polynomials over finite fields (with Boolean algebra and propositional logic as special cases). Polynomials are used to represent the basic dynamic equations for the processes (controller and plant) as well as static properties of these. Temporal algebra (or temporal logic) is used to represent specifications of system behavior. We use this approach to model the landing gear controller from a partial documentation as well as the complete implementation in Pascal. We also provide temporal algebra interpretations of the specifications made available to us. Finally we perform a number of symbolic analyses (or verifications) on the complete process (controller and plant). The main results are: These methods and tools scale to problems of a non trivial size, i.e. of the size found in complex system designs such as the JAS 39. A first demonstration of possible uses of these methods and tools. Several interesting avenues of continued research motivated by problems found during this application.