Identification of Low Order Equivalent Transfer Function Model of Trex-700E Helicopter from Flight Test Data

Abstract

Due to its wide applications in different missions, identification of mathematical models of Unmanned Aerial Vehicles (UAVs) from flight test data becomes necessary for development of observers for states estimation, computer simulation, systems analysis, and in particular for autonomous flight control laws design. For an arbitrarily chosen aerial vehicle, Trex-700E a single-rotor unmanned helicopter, a Low Order Equivalent System (LOES) model in longitudinal and lateral channels is identified respectively by utilizing CIFER ® system identification techniques. The flight test data is obtained at MicroPilot Inc. site by implementing piloted frequency sweep cyclic and collective inputs. Firstly, this paper presents a spectrum analysis performed on the input excitation signals of the flight tests. Secondly, non-parametric frequency-response models for on-axis longitudinal and lateral responses are acquired. Finally, a second-order transfer function model is identified for the longitudinal and lateral response respectively. The results show that LOES model for shortperiod mode can effectively predict the UAV system’s relevant response. However, for lateral mode, the identified LOES model needs to be modified further with more flight test data.