Identification of powered parafoil-vehicle dynamics from modelling and flight test data

摘要

During the final approach and landing phase of the X-38/Crew Return Vehicle, asteerable parafoil is used to maneuver and land at a targeted ground base underautonomous control. To simulate and verify performance of the onboard ParafoilGuidance, Navigation and Control system (PGNC), a commercial powered parafoil-vehicle, called the Buckeye consisting of a parafoil and vehicle two-body system likethe X-38/CRV was modified to accommodate the avionics and scale-downed parafoilfor aerodynamic similarity and a series of flight tests were conducted.Dynamic modelling and system identification results for the Buckeye are de-scribed in this dissertation. The vehicle dynamics are modelled as all 8 degrees-of-freedom system comprising 6 states for the parafoil and 2 states for the relative pitchand yaw motion of the vehicle with respect to the parafoil. Modal analysis for thelinearized model from the nonlinear model shows the number and order of dynamicmodes as well as the system is controllable and observable. For system identifica-tion, the overparameterized Observer/Kalman Filter Identification (OKID) methodis applied to identify a linear model of the Buckeye two-body system from the flightdata assuming that disturbances at a calm day are represented as periodic distur-bances. The identification results show that the overparameterized OKID works wellfor powered parafoil-vehicle two-body system identification under calm day condi-tions using flight data. For the data with possible discrete gusts the OKID showslimitation to identify a linearized model properly. Several sensor packages includingairdata and Inertial Measurement Unit are designed and installed for the parametersfor identification. The sensor packages successfully supply data of the parameters foridentification and suggest a feasible, low cost method for the parafoil-vehicle two-bodydynamic parameters.