PySimulator and Modelica Based Collaborative System Design Simulation Analysis Environment for Energy System Applications

Executive Summary:

The Systems for Green Operations ITD of Clean Sky aimed to demonstrate substantial environmental and economic benefits of more electric aircraft systems technologies. However, the design and validation of such highly integrated systems needs more co-operative and collaborative development processes involving aircraft, engine, and equipment manufacturers.

At the current state-of-the-art it is often the case that each application area uses different design and modelling tools, which cannot easily communicate and connect to each other for total system design and validation. A related problem is the current dependence on specific tool vendors which hampers total system design when tools from several vendors need to be used. Total system validation is usually difficult since unit and regression testing can normally only be performed within one tool at a time, instead of for the whole system design. Connecting models different suppliers and simulation tools for a unified system simulation is often difficult and costly, if at all possible.

An important goal was to enable a more co-operative and collaborative development processes involving aircraft, engine, and equipment manufacturers. The design process had to be supported through advanced modelling and simulation capabilities. Therefore the goal of the Green Operations ITD of Clean Sky consortium was to define standardized modelling methods and tools in each phase of the energy system design process. This was examined for instance in the Use Case: “Development of a modular energy system simulation tool-chain” as part of SGO WP2. In this example, collaborators from the aircraft industry use the FMI Standard in order to integrate their models in a total system simulation.

Whereas this work had largely been conducted successfully, it also revealed problems and a need for more light-weighted and freely accessible simulation tools for collaborative modelling and design processes of total complex systems.

In particular there was a need for innovations in the following areas:

• The dependence on one specific tool vendor in the design process should be greatly reduced to not hamper total system design.
• Unit and regression testing should be applied over different tools in order that models can be safely utilized in different tools.
• Connecting models from different suppliers and simulation tools for a unified system simulation should be possible in a freely accessible tool for widespread use and dissemination.

The basis to reach these goals within this project was PySimulator (https://github.com/PySimulator/PySimulator/), a Python based, open source environment for simulating FMU’s and running other simulation engines such as Dymola or OpenModelica (www.openmodelica.org).

The central idea of PySimulator was to provide a generic framework to perform simulations with different simulation engines in a convenient way, to organize the persistent storage of small and huge result data sets, to provide plotting and other post-processing feature such as signal processing or linear system analysis, and to export simulation and analysis results to other environments such as Matlab.

The major innovation of PySimulator was its plugin system: Nearly all operations are defined as plugins with defined interfaces. Several useful plugins are already provided, but anyone can extend this environment by his/her own plugins and there is no formal difference to plugins already provided.

Thus, the PySimulator open source tool can be used by each partner independently of any commercial simulation environment used for FMU generation.

The work in this project aimed at significantly improving the capabilities of PySimulator by:

• Adding an additional simulation plugin as well as improving the existing PySimulator framework and OpenModelica plugin.
• Developing capabilities in PySimulator to perform unit and regression testing over models from multiple tools.
• Developing capabilities in PySimulator for simulating connected FMUs (i.e., compiled and exported models) from several tools. This is needed in total system model simulation.

The developed framework was the first open-source project that supports simulation of connected FMUs for both Model Exchange and Co-Simulation. Also, no other commercial framework exists that supports direct simulation of connected Model Exchange FMUs.