An approach to implement a Programmable Logic Controller from real-time software components

Abstract

This paper proposes an approach to implement a Programmable Logic Controller (PLC) from real-time software components following the International Industrial Standard IEC61499. According to this standard, a Function Block is an event triggered component owning data and a control application is a network of blocks that have to satisfy end to end response time bounds according to user requirements. To correctly deploy these blocks in feasible OS tasks of the PLC, we propose a hybrid scheduling approach that combines static non-preemptive and online preemptive policies where the static policy allows the construction of sequencings that satisfy temporal constraints. We transform these sequencings into conditional OS tasks of the execution environment before we apply the online policy to check the preemptive feasibility of these tasks.