Abstract
The airspeed is an important feedback signal for flight control, and its measurement accuracy is related to the safety of aircraft, especially for hybrid vertical takeoff and landing (VTOL) unmanned aerial vehicles (UAV) in the transition phase. However, offline calibration of the pitot tube cannot fully simulate the situation in real cases, and this is why online calibration after installation is necessary. In addition, the environmental wind field creates a high risk for the conversion flight of a hybrid UAV, thus real-time wind field measurement of the flight field has great significance for the flight path planning of the conversion process. In this article, an innovative method for online calibration of pitot tube and wind field estimation is proposed. After establishing the extended Kalman filter (EKF) for estimation, an analysis method is proposed to analyze the observability of EKF under different flight strategies. Then, the hovering flight is selected as the experimental flight trajectory. The laboratory computer simulation and flight experiment results validate the theory and prove that the proposed method could re-calibrate the scale factor of the pitot tube and estimate the wind field.
Highlights
During recent decades, unmanned aerial vehicles (UAVs) have been increasingly used in civil and military applications which include search and rescue operations [1], area mapping [2], weather monitoring [3], and agricultural operations [4]
As the hybrid vertical takeoff and landing (VTOL) is a fusion of fixed-wing UAV and rotorcraft UAV, the conversion process of two flight modes is accompanied by changes in the actuators and control law, and the control accuracy at this stage directly affects the safety of the hybrid VTOL [10,11]
The measurements from an integrated navigation system and pitot tube are used, and a method based on an extended Kalman filter (EKF) for online calibration of airspeed tube and measurement of wind field is proposed
Summary
During recent decades, unmanned aerial vehicles (UAVs) have been increasingly used in civil and military applications which include search and rescue operations [1], area mapping [2], weather monitoring [3], and agricultural operations [4]. As the hybrid VTOL is a fusion of fixed-wing UAV and rotorcraft UAV, the conversion process of two flight modes is accompanied by changes in the actuators and control law, and the control accuracy at this stage directly affects the safety of the hybrid VTOL [10,11] At this phase, the switching criterion of two different control strategies depends on the change of airspeed. The measurements from an integrated navigation system and pitot tube are used, and a method based on an extended Kalman filter (EKF) for online calibration of airspeed tube and measurement of wind field is proposed.
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