System Identification of Powered Parafoil-Vehicle from Flight Test Data

The X-38/Crew Return Vehicle, a lifting body reentry vehicle, has been developed as a lifeboat in case of emergency at the International Space Station. To simulate and verify the performance of the onboard Parafoil Guidance, Navigation and Control system, a commercial powered parafoil vehicle, known as Buckeye, was modified to accommodate the avionics and reduced-scale parafoil for aerodynamic similarity. Dynamic modeling and system identification results for the Buckeye are described in this paper. The vehicle dynamics are modeled as an eight degrees-offreedom system comprising the six states for the parafoil and two states for the relative pitch and yaw angles of the vehicle with respect to the parafoil. Controllability and observability analyses are done using the Parafoil Dynamic Simulator, a six degreesof- freedom nonlinear simulation code used prior to the actual flight tests. For system identification, the Observer/Kalman Filter Identification method is applied to reduce the flight test data, as well as simulated ones from the Parafoil Dynamic Simulator for small excitations. The identification results demonstrate that this approach works well for parafoil-vehicle system identification using flight data. 2003 by Gi-Bong Hur and John Valasek.

System Identification of Powered Parafoil-Vehicle from Flight Test Data Conference Paper