An Open-Source Framework for Efficient Co-simulation of Fluid Power Systems

Simulation of fluid power systems typically requires models from multiple disciplines.Achieving accurate load dynamics for a system with complex geometry, for example, may require both a 1D model of the hydraulic circuit and a 3D multi-body model.However, most simulation tools are limited to a single discipline.A solution to these kinds of problems is co-simulation, where different tools are coupled and simulated together.Co-simulation can provide increased accuracy, improved modularity and facilitated collaboration between different organizations.Unfortunately, tool coupling typically requires tedious and error-prone manual work.It may also introduce numerical problems.For these reasons, co-simulation is often avoided as long as possible.These problems have been addressed by the development of an open-source framework for asynchronous co-simulation.Simulation tools can be interconnected through a stand-alone master simulation tool.An extensive range of tools is also supported via the Functional Mockup Interface standard.A graphical user interface has been implemented in the OpenModelica Connection Editor.System models can be created and edited from both a schematic view and a 3D view.Numerical robustness is enforced by the use of transmission line modelling.A minimalistic programming interface consisting of only two functions is used.An example model consisting of a hydraulic crane with two arms, two actuators and a hanging load is used to verify the framework.The composite model consists of nine multi-body models, one hydraulic system model and a controller.It is shown that models from various simulation tools can be replaced with a minimal amount of user input.