Maneuverability is a key factor to determine whether a helicopter could finish certain flight missions successfully or not. Inverse simulation is commonly used to calculate the pilot controls of a helicopter to comple...Maneuverability is a key factor to determine whether a helicopter could finish certain flight missions successfully or not. Inverse simulation is commonly used to calculate the pilot controls of a helicopter to complete a certain kind of maneuver flight and to assess its maneuverability.A general method for inverse simulation of maneuver flight for helicopters with the flight control system online is developed in this paper. A general mathematical describing function is established to provide mathematical descriptions of different kinds of maneuvers. A comprehensive control solver based on the optimal linear quadratic regulator theory is developed to calculate the pilot controls of different maneuvers. The coupling problem between pilot controls and flight control system outputs is well solved by taking the flight control system model into the control solver. Inverse simulation of three different kinds of maneuvers with different agility requirements defined in the ADS-33 E-PRF is implemented based on the developed method for a UH-60 helicopter. The results show that the method developed in this paper can solve the closed-loop inverse simulation problem of helicopter maneuver flight with high reliability as well as efficiency.展开更多
Aero-engine rotor systems installed in aircraft are considered to have a base motion.In this paper,a flexible asymmetric rotor system is modeled considering the nonlinear supports of ball bearings and Squeeze Film Dam...Aero-engine rotor systems installed in aircraft are considered to have a base motion.In this paper,a flexible asymmetric rotor system is modeled considering the nonlinear supports of ball bearings and Squeeze Film Dampers(SFDs),and the dynamic characteristics of the rotor system under maneuvering flight are systematically studied.Effects of the translational accelerative motions,the angular motions and the pitching flight with combined translational and angular motions on nonlinear dynamic behavior of the rotor system are investigated.The results show that,due to the nonlinear coupled effects among the rotor,ball bearings and SFDs,within the first bending resonance region,responses of the rotor show obvious nonlinear characteristics such as bistable phenomenon,amplitude jumping phenomenon and non-synchronous vibration.Translational acceleration motion of the aircraft leads to axis offset of the rotor system and thus results in the reduction and the final disappearance of the bistable rotating speed region.The pitching angular motion mainly affects rotational vibration of the rotor system,and thus further induces their transverse vibrations.For the pitching flight with combined translational and angular motions,a critical flight parameter is found to correspond to the conversion of two steady responses of the rotor system,in which one response displays small amplitude and synchronous vibration,and the other shows large amplitude and non-synchronous vibration.展开更多
Wing motion of a dragonfly in the maneuvering flight, which was measured by Wang et al. [1]was investigated. Equations of motion for a maneuvering flight of an insect were derived. These equations were applied for an...Wing motion of a dragonfly in the maneuvering flight, which was measured by Wang et al. [1]was investigated. Equations of motion for a maneuvering flight of an insect were derived. These equations were applied for analyzing the maneuvering flight. Inertial forces and moments acting on a body and wings were estimated by using these equations and the measured motions of the body and the wings. The results indicated the following characteristics of this flight: (1)The phase difference in flapping motion between the two fore wings and two hind wings, and the phase difference between the flapping motion and the feathering motion of the four wings are equal to those in a steady forward flight with the maximum efficiency. (2)The camber change and the feathering motion were mainly controlled by muscles at the wing bases.展开更多
Maneuvering flight substantially affects the dynamic behavior of rotors;particularly,such flight may cause rubbing between a rotor and stator,which is one of the most serious damages in aircraft engines.In this paper,...Maneuvering flight substantially affects the dynamic behavior of rotors;particularly,such flight may cause rubbing between a rotor and stator,which is one of the most serious damages in aircraft engines.In this paper,a nonlinear dynamic model for describing the dynamic characteristics of a rub-impact rotor system during maneuvering flight is established based on the Lagrange equations.Subsequently,numerical simulations employing the Newmark method are performed,delving into the detailed discussion of the influence of parameters such as rotational speed and maneuvering flight on the transient and steady-state responses of the rotor system.The effect mechanism of maneuver load and its coupling with rub impact is revealed.The results show that the impact response induced by maneuvering flight is more obvious in the subcritical state than in the supercritical state.The additional stiffness and damping are also induced;in particular,the additional damping has a coupling effect.Moreover,the rub impact imposes an additional constraint on the rotor system,thereby weakening the influence of the maneuver load and becoming the major factor that determines the dynamic behavior of the rotor system at high speeds.展开更多
In view of the engineering background that CK drone aircraft needs modification and upgrading to improve its maneuvering performance,numerical research and analysis of air inlet aerodynamic performance are carried out...In view of the engineering background that CK drone aircraft needs modification and upgrading to improve its maneuvering performance,numerical research and analysis of air inlet aerodynamic performance are carried out.Firstly,based on the introduction of the theoretical knowledge involved in aircraft maneuvering flight,parameters such as aircraft attitude and engine mass flow etc.required for the aerodynamic performance calculation of CK drone aircraft air inlet are determined.By analyzing the test data of WP6 engine inlet distortion simulation board,the typical indexes are extracted as the basis for evaluating the air inlet performance of CK drone aircraft.Then,the aerodynamic characteristics of the inlet of CK drone aircraft under different maneuvering conditions are numerically studied,and the total pressure recovery coefficient and pressure distortion index of the outlet section are obtained.Several conclusions and suggestions are formed after the study.When CK drone aircraft flies at positive angle of attack,the inlet has good aerodynamic characteristics,which can meet the requirements of engine intake during high maneuverable flight.In the flight of negative angle of attack,the total pressure loss and pressure distortion at the outlet section of air inlet increase sharply,which cannot guarantee the stable working of the engine.On the premise that the aircraft attitude is satisfied,CK drone aircraft can use three engine thrust states of"Rated","Modified rated"and"Maximum"for high maneuverable flight.展开更多
A discussion is devoted to the design of an adaptive flight control system of the armed helicopter using wavelet neural network method. Firstly, the control loop of the attitude angle is designed with a dynamic invers...A discussion is devoted to the design of an adaptive flight control system of the armed helicopter using wavelet neural network method. Firstly, the control loop of the attitude angle is designed with a dynamic inversion scheme in a quick loop and a slow loop. respectively. Then, in order to compensate the error caused by dynamic inversion, the adaptive flight control system of the armed helicopter using wavelet neural network method is put forward, so the BP wavelet neural network and the Lyapunov stable wavelet neural network are used to design the helicopter flight control system. Finally, the typical maneuver flight is simulated to demonstrate its validity and effectiveness. Result proves that the wavelet neural network has an engineering practical value and the effect of WNN is good.展开更多
In view of engineering application, it is practicable to decompose the aerodynamics into three components： the static aerodynamics, the aerodynamic increment due to steady rotations, and the aerodynamic increment due...In view of engineering application, it is practicable to decompose the aerodynamics into three components： the static aerodynamics, the aerodynamic increment due to steady rotations, and the aerodynamic increment due to unsteady separated and vortical flow. The first and the second components can be presented in conventional forms, while the third is described using a one-order differential equation and a radial-basis-function （RBF） network. For an aircraft configuration, the mathematical models of 6- component aerodynamic coefficients are set up from the wind tunnel test data of pitch, yaw, roll, and coupled yawroll large-amplitude oscillations. The flight dynamics of an aircraft is studied by the bifurcation analysis technique in the case of quasi-steady aerodynamics and unsteady aerodynam- ics, respectively. The results show that： （1） unsteady aerodynamics has no effect upon the existence of trim points, but affects their stability; （2） unsteady aerodynamics has great effects upon the existence, stability, and amplitudes of periodic solutions; and （3） unsteady aerodynamics changes the stable regions of trim points obviously. Furthermore, the dynamic responses of the aircraft to elevator deflections are inspected. It is shown that the unsteady aerodynamics is beneficial to dynamic stability for the present aircraft. Finally, the effects of unsteady aerodynamics on the post-stall maneuverability展开更多
The super-maneuver flight performance has a very high tactical value, and the development of this tactical value has great significance. A discussion is devoted to the study of intelligent control methods and technolo...The super-maneuver flight performance has a very high tactical value, and the development of this tactical value has great significance. A discussion is devoted to the study of intelligent control methods and technologies of real-time distributed 3-dimensional animation simulation for the super-maneuverable attack of new generational fighter in this paper. A flight control system of super-maneuver is reconstructed by adopting three layers BP neural networks of number 3, and the fire/flight coupler is designed by introducing a fuzzy control rule whose universe of discourse and gain are regulated adaptively on the line. Furthermore, a new method of real-time distributed 3-dimensional animation simulation is put forward, and a real-time distributed 3-dimensional animation simulation tool platform is constructed in this paper. The simulation result is lifelike, perceivable directly and useful.展开更多
The Dash Stop flight at the extreme condition is the primary interest of this study. This paper describes some research on the flight characteristics of helicopter in Dash Stop. A set of equations which govern the Das...The Dash Stop flight at the extreme condition is the primary interest of this study. This paper describes some research on the flight characteristics of helicopter in Dash Stop. A set of equations which govern the Dash Stop is developed. A method which determines the acceleration and deceleration is proposed. Formulas are then developed which relate the aircraft angular rates and attitudes to flight speed, angle of attack and acceleration or deceleration. Finally the DOLPHIN helicopter is taken as an example to calculate its acceleration/deceleration capability, pilot control and aircraft attitudes in space. It is found that the results are reasonable.展开更多
基金co-supported by the National Natural Science Foundation of China (No. 61503183)the Aeronautical Science Foundation of China (No. 2015ZA52002)
文摘Maneuverability is a key factor to determine whether a helicopter could finish certain flight missions successfully or not. Inverse simulation is commonly used to calculate the pilot controls of a helicopter to complete a certain kind of maneuver flight and to assess its maneuverability.A general method for inverse simulation of maneuver flight for helicopters with the flight control system online is developed in this paper. A general mathematical describing function is established to provide mathematical descriptions of different kinds of maneuvers. A comprehensive control solver based on the optimal linear quadratic regulator theory is developed to calculate the pilot controls of different maneuvers. The coupling problem between pilot controls and flight control system outputs is well solved by taking the flight control system model into the control solver. Inverse simulation of three different kinds of maneuvers with different agility requirements defined in the ADS-33 E-PRF is implemented based on the developed method for a UH-60 helicopter. The results show that the method developed in this paper can solve the closed-loop inverse simulation problem of helicopter maneuver flight with high reliability as well as efficiency.
基金the National Key Basic Research Program of China(No.2015CB057400)the National Natural Science Foundation of China(Nos.11672201 and 11872045)the Major Special Basic Research Projects for Aeroengines and Gas Turbines(No.2017-IV-0008-0045)。
文摘Aero-engine rotor systems installed in aircraft are considered to have a base motion.In this paper,a flexible asymmetric rotor system is modeled considering the nonlinear supports of ball bearings and Squeeze Film Dampers(SFDs),and the dynamic characteristics of the rotor system under maneuvering flight are systematically studied.Effects of the translational accelerative motions,the angular motions and the pitching flight with combined translational and angular motions on nonlinear dynamic behavior of the rotor system are investigated.The results show that,due to the nonlinear coupled effects among the rotor,ball bearings and SFDs,within the first bending resonance region,responses of the rotor show obvious nonlinear characteristics such as bistable phenomenon,amplitude jumping phenomenon and non-synchronous vibration.Translational acceleration motion of the aircraft leads to axis offset of the rotor system and thus results in the reduction and the final disappearance of the bistable rotating speed region.The pitching angular motion mainly affects rotational vibration of the rotor system,and thus further induces their transverse vibrations.For the pitching flight with combined translational and angular motions,a critical flight parameter is found to correspond to the conversion of two steady responses of the rotor system,in which one response displays small amplitude and synchronous vibration,and the other shows large amplitude and non-synchronous vibration.
文摘Wing motion of a dragonfly in the maneuvering flight, which was measured by Wang et al. [1]was investigated. Equations of motion for a maneuvering flight of an insect were derived. These equations were applied for analyzing the maneuvering flight. Inertial forces and moments acting on a body and wings were estimated by using these equations and the measured motions of the body and the wings. The results indicated the following characteristics of this flight: (1)The phase difference in flapping motion between the two fore wings and two hind wings, and the phase difference between the flapping motion and the feathering motion of the four wings are equal to those in a steady forward flight with the maximum efficiency. (2)The camber change and the feathering motion were mainly controlled by muscles at the wing bases.
基金supported by the National Natural Science Foundation of China(No.12202229)the Science Center for Gas Turbine Project,China(No.P2022-B-III-002-001)the Scientific Research Projects of Tianjin Education Commission,China(Nos.2020KJ018,2020KJ060).
文摘Maneuvering flight substantially affects the dynamic behavior of rotors;particularly,such flight may cause rubbing between a rotor and stator,which is one of the most serious damages in aircraft engines.In this paper,a nonlinear dynamic model for describing the dynamic characteristics of a rub-impact rotor system during maneuvering flight is established based on the Lagrange equations.Subsequently,numerical simulations employing the Newmark method are performed,delving into the detailed discussion of the influence of parameters such as rotational speed and maneuvering flight on the transient and steady-state responses of the rotor system.The effect mechanism of maneuver load and its coupling with rub impact is revealed.The results show that the impact response induced by maneuvering flight is more obvious in the subcritical state than in the supercritical state.The additional stiffness and damping are also induced;in particular,the additional damping has a coupling effect.Moreover,the rub impact imposes an additional constraint on the rotor system,thereby weakening the influence of the maneuver load and becoming the major factor that determines the dynamic behavior of the rotor system at high speeds.
基金supported by the Fundamental Research Funds for the Central Universities(No.56XCA2004806)。
文摘In view of the engineering background that CK drone aircraft needs modification and upgrading to improve its maneuvering performance,numerical research and analysis of air inlet aerodynamic performance are carried out.Firstly,based on the introduction of the theoretical knowledge involved in aircraft maneuvering flight,parameters such as aircraft attitude and engine mass flow etc.required for the aerodynamic performance calculation of CK drone aircraft air inlet are determined.By analyzing the test data of WP6 engine inlet distortion simulation board,the typical indexes are extracted as the basis for evaluating the air inlet performance of CK drone aircraft.Then,the aerodynamic characteristics of the inlet of CK drone aircraft under different maneuvering conditions are numerically studied,and the total pressure recovery coefficient and pressure distortion index of the outlet section are obtained.Several conclusions and suggestions are formed after the study.When CK drone aircraft flies at positive angle of attack,the inlet has good aerodynamic characteristics,which can meet the requirements of engine intake during high maneuverable flight.In the flight of negative angle of attack,the total pressure loss and pressure distortion at the outlet section of air inlet increase sharply,which cannot guarantee the stable working of the engine.On the premise that the aircraft attitude is satisfied,CK drone aircraft can use three engine thrust states of"Rated","Modified rated"and"Maximum"for high maneuverable flight.
文摘A discussion is devoted to the design of an adaptive flight control system of the armed helicopter using wavelet neural network method. Firstly, the control loop of the attitude angle is designed with a dynamic inversion scheme in a quick loop and a slow loop. respectively. Then, in order to compensate the error caused by dynamic inversion, the adaptive flight control system of the armed helicopter using wavelet neural network method is put forward, so the BP wavelet neural network and the Lyapunov stable wavelet neural network are used to design the helicopter flight control system. Finally, the typical maneuver flight is simulated to demonstrate its validity and effectiveness. Result proves that the wavelet neural network has an engineering practical value and the effect of WNN is good.
文摘In view of engineering application, it is practicable to decompose the aerodynamics into three components： the static aerodynamics, the aerodynamic increment due to steady rotations, and the aerodynamic increment due to unsteady separated and vortical flow. The first and the second components can be presented in conventional forms, while the third is described using a one-order differential equation and a radial-basis-function （RBF） network. For an aircraft configuration, the mathematical models of 6- component aerodynamic coefficients are set up from the wind tunnel test data of pitch, yaw, roll, and coupled yawroll large-amplitude oscillations. The flight dynamics of an aircraft is studied by the bifurcation analysis technique in the case of quasi-steady aerodynamics and unsteady aerodynam- ics, respectively. The results show that： （1） unsteady aerodynamics has no effect upon the existence of trim points, but affects their stability; （2） unsteady aerodynamics has great effects upon the existence, stability, and amplitudes of periodic solutions; and （3） unsteady aerodynamics changes the stable regions of trim points obviously. Furthermore, the dynamic responses of the aircraft to elevator deflections are inspected. It is shown that the unsteady aerodynamics is beneficial to dynamic stability for the present aircraft. Finally, the effects of unsteady aerodynamics on the post-stall maneuverability
文摘The super-maneuver flight performance has a very high tactical value, and the development of this tactical value has great significance. A discussion is devoted to the study of intelligent control methods and technologies of real-time distributed 3-dimensional animation simulation for the super-maneuverable attack of new generational fighter in this paper. A flight control system of super-maneuver is reconstructed by adopting three layers BP neural networks of number 3, and the fire/flight coupler is designed by introducing a fuzzy control rule whose universe of discourse and gain are regulated adaptively on the line. Furthermore, a new method of real-time distributed 3-dimensional animation simulation is put forward, and a real-time distributed 3-dimensional animation simulation tool platform is constructed in this paper. The simulation result is lifelike, perceivable directly and useful.
文摘The Dash Stop flight at the extreme condition is the primary interest of this study. This paper describes some research on the flight characteristics of helicopter in Dash Stop. A set of equations which govern the Dash Stop is developed. A method which determines the acceleration and deceleration is proposed. Formulas are then developed which relate the aircraft angular rates and attitudes to flight speed, angle of attack and acceleration or deceleration. Finally the DOLPHIN helicopter is taken as an example to calculate its acceleration/deceleration capability, pilot control and aircraft attitudes in space. It is found that the results are reasonable.
