On the difficulities of real-time co-simulation

In a co-simulation, subsystems are coupled via their in- and outputs to simulate the overall system behaviour. The subsystems are modelled in their domain specfic simulation tools. The task changes if one coupled subsystem represents a real-time system. A real-time system which has to guarantees hard-real-time conditions influences the co-simulation concept: now the co-simulation also has to fulfill hard-real-time conditions. This type of co-simulation is called real-time co-simulation. The most important difference to a non-real-time co-simulation is the time correct overall simulation speed with respect to the involved real-time systems. To achieve this, all subsystems in form of non-real-time systems have to be synchronised to the involved real-time systems. The focus of this work lies on the problems that occur in a real-time co-simulation environment compared to a classical one. A concept to handle the additional problems is outlined and tested on an example real-time co-simulation