Using cyclic executives for achieving closed loop co-simulation

Co-simulation between models that focus in different aspects of the same system is a powerful tool during the design of a system. In this paper, a co-simulation application that closes the loop between the process model and the control system, running in different software tools, is presented. The target systems are Industrial Process Measurement and Control Systems (IPMCS) that usually are implemented using PLCs as the primary control equipment. The configuration of the co-simulation is achieved by extracting information from the software model of the system being designed. Mainly, the concurrent control algorithms as well as their temporal requirements (period and priority) and the process model input/output variables are used for designing a simple cyclic executive. This cyclic executive marks the time instants in which data exchange for each control loop must be performed. These synchronization times are used by the cosimulation application which allows performing incremental validations of the control system before its implementation. The framework is based on CORBA middleware. This middleware allows performing the co-simulation among heterogeneous and distributed tools.