Reconfigurable Hardware-in-the-Loop Test Bench for the SHEFEX2 Hybrid Navigation System Experiment

Abstract

The Hybrid Navigation System is being developed to achieve the required attitude accuracy and calculate a navigation solution for the SHEFEX2 mission, which will be launched in February 2012 from And\o ya Rocket Range in Norway by the German Aerospace Center (Deutsches-Zentrum f{\"{u}}r Luft- und Raumfahrt, DLR). This system fuses data from an IMU, GPS receiver, and star tracker using the extended Kalman filter. For testing it needs a realistic software- and hardware-in-the-loop test bench that can simulate the expected flight conditions and test the system. The hardware test bench requirements include: real-time simulation progression, accurate synchronization of all components, and providing stimulation inputs for the GPS receiver, star tracker and gyro instruments (inside the IMU) representative of the expected flight profile. Another key requirement is that the test bench must be easily reconfigurable by swapping real and modeled instruments. This allows the system to be tested with variable levels of complexity, which decreases debugging time by allowing the user to separate or remove the problem points by simply swapping cables. The developed software-in-the-loop simulation consists of the navigation flight code wrapped in a Simulink s-function and fed by several high-fidelity Matlab/Simulink models which simulate the rocket dynamics and system sensors. The hardware-in-the-loop test bench runs the models from the software simulation on a dSPACE real-time simulator, which feeds the modeled sensor outputs to the hybrid navigation system's navigation computer. With the help of a Spirent GSS7700 GPS signal generator, a Jenoptik Optical Sky field Simulator, and an Acutronic 3-axis rotation table all synchronized to the dSPACE simulation, the modeled sensors can be replaced with real sensors fed with stimulated input. Navigation results from the hardware test bench are compared with results from the software-in-the-loop simulation to ensure that the hardware-in-the-loop simulation is working correctly.