Simulation-based System Engineering in the Virtual Satellite Project

Abstract

The development of complex space systems requires the collaboration of specialists in a variety of disciplines. The main challenge of the "concurrent engineering" approach is to keep a consistent view of the system and to organize the data exchange between the specialists appropriately. One way to achieve system model consistency is to use a shared SysML model. Each specialist accesses the model via a discipline-specific view. Unfortunately, SysML tools neither support the reuse of available system components or component assemblies, nor do they provide sufficient support for the data exchange among the different disciplines. To close this gap, the German Aerospace Center (DLR) in 2007 initiated the "Virtual Satellite" project. At the heart of the project a system component repository keeps SysML models of system components, together with related metainformation. This includes ports of the components and information from past space projects, such as parameterizations and configurations. In addition, complex models of entire spacecraft configurations can be stored in the repository. As a first step in the development of a new spacecraft model, the system engineer browses the repository in search of an existing SysML model that fits the intended configuration as closely as possible. Components can be deleted and others can be added as required. Each component model provides views for all engineering disciplines, with ports describing the discipline-specific input/output data. In a second step, for each engineering discipline the corresponding specialist uses a SysML tool to connect the open ports between components and thus completes the logical view of the system. Together with the SysML models and metadata, the repository contains static and dynamic simulation models for each component. Based on the SysML model of a complete space system, and using the simulation models of its components, an automatic transformation tool generates an executable simulation code which can be used to analyze the space system in mission scenarios. The dynamic simulation provided by the Virtual Satellite will be used to optimize the system design for new space missions at the DLR Concurrent Engineering Facility (CEF). The CEF closely follows the concept of ESA's Concurrent Design Facility (CDF). In a CEF session the team of specialists determines optimal system parameters for all disciplines. The set of all those parameters is represented by the Integrated Design Model (IDM) which is generated automatically from the Virtual Satellite system model. The Virtual Satellite approach will improve the system development process in two ways: By collecting system models and metadata of earlier design studies, the repository makes the knowledge collected in those studies available for all future missions. By applying dynamic simulation early in the development process to validate the given constraints, system discrepancies will be detected early, thus saving costs and time.