Model Based Desgin Environment for Launcher Upper Stage GNC Development

The cost associated with developing flight control forms a significant part of the overall development cost. The increased demand for greater functionality and for extending the domain of applicability of future launchers leads to higher complexity of the GNC algorithms. Furthermore, there is also a need for a responsive design methodology, which can quickly adapt to changes in the requirements during the development process. These demands are stretching the current, largely manual, development process, which is fragmented in the different disciplines and activities concerning modelling, algorithm design, software coding, implementation on the avionics platform and the associated testing at the different stages. The model-based-design (MBD) philosophy presents an attractive solution in addressing the multi-disciplinary nature of the flight algorithm design task. In terms of design process, this materializes in a tight coupling between the modelling, the design and the analysis activities. An integrated design framework for the GNC development for future launcher upper stages has been realized with the 'Upper Stage Attitude Development Framework' (USACDF) research effort. USACDF has been initiated by the ESA Launcher Directorate within its Future Launcher Preparatory Program (FLPP). FLPP aims at preparing the Next Generation Launcher (NGL) by supporting activities, which increase the maturity level of launcher technologies and acquire new ones. It specifically implements a system-driven approach. The framework seamlessly covers, in a dynamic fashion, the entire design process from requirement capturing activities until verification and validation of the auto-coded GNC and the related mission and vehicle management (MVM) application software, which runs on flight representative processors and hardware (LEON II used for demonstration). The basis of the design suite relies on the commercially available MathWorks' tool-chain accompanied by the dSPACE system (see [1], [2]). However, it is not limited to the algorithm design, but also heavily using those elements, supporting model based design, automatic report generation, requirement tracing between software and specifications and automated verification, including real-time processor performance profiling. Mathworks' GNC and SW tool-chain has been augmented to physical modelling approaches, namely Modelica and EcosimPro (beside Mathworks' own SimMechanics). The particular strength of the physical modelling is the injection of failure cases directly at the physical level. This allows for designing and testing advanced failure recovery elements of the flight software. The algorithms, developed in the USACDF framework, can be run in a TASTE/RASTA/LEON environment (see [3]) via autocoding. The plant dynamics is realized on a dSPACE system connecting to RASTA via Ethernet communication. The transfer from a PC based functional engineering simulator (FES) to a LEON/dSPACE closed loop configuration can be achieved quickly and nearly automatically. The paper is organized as follows: The next section will place the USACDF approach into an overall context by discussing contributions found in the literature. Next, the limitations and constrains of the current way to develop flight control for space application are discussed. The following sections will then highlight the USACDF design suite features and explain how they answer to the needs and how they extent the domain of applicability. The last section discusses the benchmark problem, which was used to test the framework and to carry out algorithm design for some particular uppers attitude control problems.