Indexed on: 01 Mar '99Published on: 01 Mar '99Published in: Formal Methods in System Design
Formal verification of computer-based engineering systems is only meaningful if the mathematical models used are derived systematically, recording the assumptions made at each modelling stage. In this paper we give an exposition of research efforts in cooperation with aerospace industries in Sweden. We emphasize the need for modelling techniques and languages covering the whole spectrum from informal engineering documents, to hybrid mathematical models. In this modelling process we give as much weight to the physical environment as to the controlling software. In particular, we report on our experience using switched bond graphs for the modelling of hardware components in hybrid systems. We present the basic ideas underlying bond graphs and illustrate the approach by modelling an aircraft landing gear system. This system consists of actuating hydromechanic and electromechanic hardware, as well as controlling components implemented in software and electronics. We present a detailed analysis of the closed loop system with respect to safety and timeliness properties. The proofs are carried out within the proof system of Extended Duration Calculus.