The wind disturbance rejection capability of a quadrotor fixed-wing hybrid unmanned aerial vehicle (QFHUAV) in the quadrotor mode is an important factor restricting its large-scale applications. In this paper, based on static equilibrium analysis of the quadrotor mode of a QFHUAV with a wind disturbance, a method for analyzing and evaluating the wind disturbance rejection capability of the QFHUAV in the quadrotor mode is presented. The six degrees-of-freedom (6-DOF) static equilibrium equations of the QFHUAV are established in headwind and crosswind situations. The maximum wind velocity that satisfies the equilibrium equations under the constraints of the maximum thrust and torque of the quadrotor propulsion system is used to determine the wind disturbance rejection capability of the QFHUAV in the quadrotor mode. A QFHUAV with a twin-boom is used as an example to analyze and evaluate its wind disturbance rejection capability in the quadrotor mode. The configuration parameters, quadrotor propulsion system parameters, and aerodynamic parameters affecting the wind disturbance rejection capability of the QFHUAV in the quadrotor mode are presented, discussed, and explained. The yawing moment from the wind disturbance is the main factor threatening the safe flight of the QFHUAV in the quadrotor mode. The rotor disk angle, the maximum thrust of the quadrotor propulsion system, and the moment arms of the components of the quadrotor propulsion system thrust are the main factors affecting the wind disturbance rejection capability of the QFHUAV in the quadrotor mode. Increasing these parameter values is an effective approach to improve the wind disturbance rejection capability of the QFHUAV in the quadrotor mode. From the perspective of wind disturbance rejection capability, tailless and X-type layouts are better choices for QFHUAVs. The correctness of results obtained by the proposed method is verified by two flight test schemes. KeywordsWind disturbance rejection capability, quadrotor fixed-wing hybrid unmanned aerial vehicle (QFHUAV), analyze and evaluate, quadrotor mode, maximum wind velocity, factors, improvement approaches
Quad-Plane UAV(quadrotor fixed-wing hybrid vertical take-off and landing Unmanned Aerial Vehicle) is vulnerable to wind disturbance in quadrotor mode, and the performance of the electric quadrotor system directly affects its wind disturbance rejection performance. To study and optimize the wind disturbance rejection performance of the electric quadrotor system of Quad-Plane precisely and efficiently, a dynamic electric quadrotor simulation system integrating high-precision submodels of electric quadrotor system components is required. However, there are few papers on this kind of simulation system. This paper proposed a simulation system with both high computational efficiency and precision, and it can be used in optimization and flight simulation of Quad-Plane. The simulation system includes submodels of rotor, brushless direct current (BLDC) motor, electronic speed controller (ESC), and Li-ion Polymer battery. The surrogate-based rotor model is established to calculate the aerodynamic performance of the rotor in oblique flow. The BLDC motor performance calculation model considering inductance is presented and the power loss of the ESC is considered. The discharge characteristics of the battery are modeled considering the rate capacity effect. All submodels are validated and the simulation results show good agreements with test data. A flight test of Quad-Plane in quadrotor mode is conducted to validate the integrated dynamic simulation system. The results show that the simulation system has the advantages of high computational efficiency and precision. Based on the simulation system, the influence of the electric quadrotor system parameters on the performance of the electric quadrotor system, and furthermore on the wind disturbance rejection performance of the Quad-Plane are found, the conclusions are helpful to the selection and optimization of the electric quadrotor system components.
Hybrid Foil Magnetic Bearings (HFMBs) are a promising bearing technology for high-speed, oil-free turbomachinery that structurally embeds a gas foil bearing (GFB) into the inner diameter of an active magnetic bearing (AMB). The flexible foil structure provides sufficient support stiffness for the rotor, while closed-loop control allows real-time adjustment of the dynamic performance of the bearing. In this paper, the static and dynamic performance of the HFMB is measured experimentally. The effect of the control gain on the static and dynamic performance of the HFMB is highlighted. The proportional gain increases the stiffness but weakens the stability of the system, while the differential gain increases the damping but unexpectedly increases the stiffness. The static and dynamic performance of the HFMB is compared with that of the GFB. At low excitation frequencies, the stability of the GFB is higher than that of the HFMB, while as the excitation frequency is increased, the stability of the HFMB exceeds that of the GFB.
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