Original Date: 09/14/1998
Revision Date: 01/18/2007
Best Practice : Six Degrees of Freedom Simulation Development Process
Raytheon Missile Systems Company (RMSC) built a Six Degrees of Freedom (6DOF) model that simulates the prelaunch and flight operations of a missile, including atmospheric conditions and global positioning/satellite communication systems. The 6DOF model accomplishes this feat by using mathematical computer representations of missile subsystems; mass property databases; simulations of atmospheric conditions; global positioning/satellite communication systems information; and other missile flight hardware and software. RMSC has simulated various missile subsystems by creating inertial sensor, propulsion, actuator, and non-linear aero/hydro models. These subsystems handle missile guidance, navigation, control, and flight performance.
RMSC accomplishes 6DOF simulations by developing two modeling categories. The first is by creating all software non-real-time simulations for statistical analysis of navigation system and flight performance (e.g., covariance analysis, Monte Carlo simulations). The second is by using real-time, hardware-in-the-loop simulations complete with sensor representation and flight visualization capabilities. In the early stages of development, RMSC implements a progressive configuration control practice to facilitate creativity in a less-structured environment. As the simulation model matures, the company switches to a more formal configuration control for hardware and software.
RMSC’s software development work led to the Software Engineering Practices and Procedures (SEPP) for simulation software development, which uses ISO-12207 (Software Life Cycle Processes) as a guide for best commercial practice. SEPP identifies and defines various software development items such as project management organization, responsibilities, resources, and metrics; software development process and associated milestones; software engineering environment and programming standards/practices; and software configuration management and software quality assurance policies and practices.
Using the software development items along with contract requirements allow RMSC to yield a controlled software development process with predictable, manageable results. Although it currently measures the effectiveness of software development improvements in qualitative terms, RMSC noted benefits in other areas: software build/version control; completeness of problem assessment and corrective action implementations; common models for use by hardware and software simulations where possible; and internal and external task coordinations.
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