Issues to be considered on obtaining plant models for formal verification purposes

Abstract

Abstract. The development of dependable software for mechatronic systems can be a very complex and hard task. For facilitating the obtaining of dependable software for industrial controllers, some powerful software tools and analysis techniques can be used. Mainly, when using simulation and formal verification analysis techniques, it is necessary to develop plant models, in order to describe the plant behavior of those systems. However, developing a plant model implies that designer takes his (or her) decisions concerning granularity and level of abstraction of models; approach to consider for modeling (global or modular); and definition of strategies for simulation and formal verification tasks. This paper intends to highlight some aspects that can be considered for taking into account those decisions. For this purpose, it is presented a case study and there are illustrated and discussed very important aspects concerning above exposed issues. IntroductionA mechatronic system is composed, mainly, by three parts: Controller, Plant and Human Machine Interface (HMI) (see figure 1). These parts interact and behave together, and the development of the software to be introduced in the controller, must take into account the behavior of those parts and the interrelation between them.Several steps can be performed in order to obtain a dependable controller: first, the use of methodologies for obtaining the structure of the controller's specification [1]; second, the use of a formalism to describe, formally, the intended behavior for the controller [2]; third, the use of analysis techniques, in order to guarantee the dependability of the specification [3]; and, fourth, the translation of the specification into a controller program and respective implementation on a physical controller [4]. Concerning use of analysis techniques, plant modeling is one of the bigger issues when performing simulation and formal verification tasks for obtaining dependable software for mechatronic systems [5].This paper intends to demonstrate how to obtain meaningful plant models for formal verification purposes, taking into account the aspects related with level of abstraction, granularity, modular approach and use of global or partial plant models on the process of formal verification. For achieving this purpose, the paper is organized as follows: section 2 presents the context of analysis techniques and focuses the approach on formal verification by model-checking; section 3 presents a case study, in which are presented the developed specification for the controller and some modules of the plant