An automated methodology to select functional co-simulation configurations

The development of machinery often requires system-level analysis, in which non-mechanical subsystems, such as hydraulics, need to be considered. Co-simulation allows analysts to divide a problem into subsystems and use tailored software solutions to deal individually with their respective dynamics. On the other hand, these subsystems must be coupled at particular instants in time, called communication points, through the exchange of coupling variables. Between communication points, each subsystem solver carries out the integration of its states without interacting with its environment. This may cause the integration to become unstable, especially when non-iterative co-simulation is used. The co-simulation configuration, i.e., the parameters and simulation options selected by the analyst, such as the way to handle the coupling variables or the choice of subsystem solvers, is often a critical factor regarding co-simulation stability. In practice it is difficult to anticipate which selection is the most appropriate for a particular problem, especially if some inputs come from external sources, such as human operators, and cannot be determined beforehand. We put forward a methodology to automatically determine a stable and computationally efficient configuration for Jacobi-scheme co-simulation. The method uses energy residuals to gain insight into co-simulation stability. The relation between energy residual and communication step-size is exploited to monitor co-simulation accuracy during a series of tests in which the external inputs are replaced with predetermined input functions. The method was tested with hydraulically actuated mechanical examples. Results indicate that the proposed method can be used to find stable and accurate configurations for co-simulation applications.