In the Clean Sky consortium, several members were working on modelling and simulation of aircraft systems with the multi-domain modelling language Modelica. The final goal was to not only utilise these models for design and evaluation, but also to directly use Modelica controller models for generation of certified code in embedded systems. On one hand, this will improve the system design process, since controllers developed in Modelica won’t need to be coded manually in a different language. On the other hand, advanced nonlinear controllers could possibly be certified and thus applied on-board an aircraft.
The objective of the CertMod project was to define the type of models and the Modelica 3.3 subset that shall be handled. This subset was based on the discrete extensions of Modelica 3.3, including clocks and state machines. Once this subset was identified a prototype of a DO-178B Level A qualified code generator was developed. This code generator was an extension of the already existing SCADE Suite KCG code generator that has been qualified at Level A for DO-178B on numerous aircraft projects (Airbus A380, Boeing 787, etc.) by all civilian aeronautics certification authorities (FAA, EASA, etc.). It produced the C source code for the controller that can be guaranteed to be a correct implementation of the input Modelica model. In order to do so, a preliminary phase was added to KCG in order to perform a translation from the identified Modelica 3.3 subset into an intermediate form of KCG.
Work was performed to prototype the elements of the code generator that are necessary to qualify the tool. This included traceability from the input Modelica model down to the C generated code, various types of specification and design documents, and a procedure to extensively test the code generator.
Two representative Modelica models were provided by DLR, the topic manager, and were used to validate the code generator prototype.
The Clean Sky consortium aimed to demonstrate substantial environmental and economic benefits of more electric aircraft systems technologies. The design and validation of such highly integrated systems urged the need for more co-operative development processes involving aircraft, engine, and equipment manufacturers.
The design process has to be supported through advanced modelling and simulation capabilities. Therefore, a goal of the Clean Sky consortium was to define standardised modelling methods and tools in each phase of the energy system design process. In particular, models that span the full operating region were directly usable in control systems of the aircraft, in order to significantly improve the behaviour.