The robot pilot is a new concept of a robot system that pilots a manned aircraft,thereby forming a new type of unmanned aircraft system(UAS)that makes full use of the platform maturity,load capacity,and airworthiness ...The robot pilot is a new concept of a robot system that pilots a manned aircraft,thereby forming a new type of unmanned aircraft system(UAS)that makes full use of the platform maturity,load capacity,and airworthiness of existing manned aircraft while greatly expanding the operation and application fields of UASs.In this research,the implementation and advantages of the robot pilot concept are discussed in detail,and a helicopter robot pilot is proposed to fly manned helicopters.The robot manipulators are designed according to the handling characteristics of the helicopter-controlling mechanism.Based on a kinematic analysis of the robot manipulators,a direct-driving method is established for the robot flight controller to reduce the time delay and control error of the robot servo process.A supporting ground station is built to realize different flight modes and the functional integration of the robot pilot.Finally,a prototype of the helicopter robot pilot is processed and installed in a helicopter to carry out flight tests.The test results show that the robot pilot can independently fly the helicopter to realize forward flight,backward flight,side flight,and turning flight,which verifies the effectiveness of the helicopter robot pilot.展开更多
In this letter, a piezoaeroelastic energy harvester based on an airfoil with double plunge degrees of freedom is proposed to additionally take advantage of the vibrational energy of the airfoil pitch motion. An analyt...In this letter, a piezoaeroelastic energy harvester based on an airfoil with double plunge degrees of freedom is proposed to additionally take advantage of the vibrational energy of the airfoil pitch motion. An analytical model of the proposed energy harvesting system is built and compared with an equivalent model using the well-explored pitch-plunge configuration. The dynamic response and average power output of the harvester are numerically studied as the flow velocity exceeds the cut-in speed (flutter speed). It is found that the harvester with double-plunge configuration generates 4%-10% more power with varying flow velocities while reducing 670 of the cut-in speed than its counterpart.展开更多
The arresting process of carrier-based aircraft is widely recognized as a challenging task,characterized by the highest accident rate among all carrier-based aircraft operations.Dynamic simulation plays a crucial role...The arresting process of carrier-based aircraft is widely recognized as a challenging task,characterized by the highest accident rate among all carrier-based aircraft operations.Dynamic simulation plays a crucial role in assessing the intricate responses of the arresting process,favoring the design of carrier-based aircraft.An efficient and accurate rigid-flexible coupling model for analyzing the dynamic response of the arresting process is proposed.By combining the dynamic characteristics of airframe,landing gear,arresting hook and arresting gear system,the rigid-flexible coupling dynamic model is established to reflect the relative motion of the coupling parts and arresting load.The dynamic model is verified through simulations of landing gear landing drops and by comparing the arresting simulation results with corresponding data in the US military standard.Additionally,simulations of the arresting process under different off-center distance and aircraft yaw angle are conducted to obtain the dynamic response of the aircraft during the arresting process.The result indicates that the rigid-flexible coupling dynamic model proposed is effective for analyzing the arresting dynamics response of carrier-based aircraft.The axial force of the arresting cable on both sides of the hook engagement point,pitch and yaw angle of aircraft are inconsistent under yaw and off-center arresting.The analysis method and obtained results provide valuable references for assessing the dynamic responses of carrier-based aircraft during arresting process and offer valuable in-sights in the design of carrier-based aircraft.展开更多
“Ionic wind”generators are used as the main propulsion system in ion propulsion unmanned aerial vehicles(UAVs).Owing to the large size and poor stiffness of the electrode array in the propulsion system,the electrode...“Ionic wind”generators are used as the main propulsion system in ion propulsion unmanned aerial vehicles(UAVs).Owing to the large size and poor stiffness of the electrode array in the propulsion system,the electrode array is prone to deformation under the flight load.In this work,the thrust characteristics and static aeroelastic properties of“ionic wind”propulsion systems were analyzed in detail.The simulation model for an“ionic wind”propulsion system was established by coupling a two-dimensional gas discharge model with a gas dynamics model.The influences of electrode voltage,spacing,size,and shape on the performance of the propulsion system were investigated.The fluid-solid interaction method was used to solve static aeroelastic characteristics under deformation.The aerodynamic and thrust performances of the elastic state and the rigid state were compared.It was found that the operating voltage,the distance between two electrodes,and the emitter radius had greater impacts on the thrust of the propulsion system.The propulsion system had a small contribution to the lift but a large contribution to the drag.In the elastic state,the lift coefficient accounted for 12.2%,and the drag coefficient accounted for 25.8%.Under the action of the downwash airflow from the wing,the propulsion system formed an upward moment around the center of mass,which contributed greatly to the pitching moment derivative of the whole aircraft.In the elastic state,the pitching moment derivative accounted for 29.7%.After elastic deformation,the thrust action point moved upward by 28.7 mm.Hence,the no lift pitching moment is reduced by 0.104 N$m,and the pitching moment coefficient is reduced by 0.014,causing a great impact on the longitudinal trimming of the whole aircraft.展开更多
Morphing wings can improve aircraft performance during different flight phases.Recently research has focused on steady aerodynamic characteristics of the morphing wing with a flexible trailing-edge,and the unsteady ae...Morphing wings can improve aircraft performance during different flight phases.Recently research has focused on steady aerodynamic characteristics of the morphing wing with a flexible trailing-edge,and the unsteady aerodynamic and stall characteristics in the deflection process of the morphing wing are worthy further investigation.The effects of the angle of attack and deflection rate on aerodynamic characteristics were examined,and based on the aerodynamic characteristics of the morphing wing,a method was developed to delay stall by using the flexible periodic trailing-edge deflection.The numerical results show that the lift coefficients in the deflection process are smaller than those in the static situation at small angles of attack,and that the higher the deflection rate is,the smaller the lift coefficients will be.On the contrary,at large angles of attack,the lift coefficients are higher than those in the static case,and they become larger with the increase of the deflection rate.Further,the periodic deflection of the flexible trailing-edge with a small deflection amplitude and high deflection rate can increase lift coefficients at the critical stall angle.展开更多
Gliding is an important flight mode for insects because it saves energy during long distance flight without wing flapping. In this study, we investigated the influence of locust wing corrugation on the aerodynamic per...Gliding is an important flight mode for insects because it saves energy during long distance flight without wing flapping. In this study, we investigated the influence of locust wing corrugation on the aerodynamic performance in gliding mode at low Reynolds number. Numerical simulations using two-dimensional Navier-Stokes equations are applied to study the gliding flight, which reveals the interaction between forewing and hindwing. The lift of the corrugated airfoil in a locust wing decreases from the wing root to the tip. Simulation results show that the pressure drags on the forewing and hindwing increase with an increase in wing thickness; while the lift-drag ratio of the airfoil is marginally affected by the corrugation on the airfoil. Geometric parameters analysis of the locust wing is also carried out, which includes the corrugation height, the corrugation placement and the shapes of leading and trailing edges.展开更多
A three-wing Flapping Wing Rotor Micro Aerial Vehicle(FWR-MAV)which can perform controlled flight is introduced and an experimental study on this vehicle is presented.A mechanically driven flapping rotary mechanism is...A three-wing Flapping Wing Rotor Micro Aerial Vehicle(FWR-MAV)which can perform controlled flight is introduced and an experimental study on this vehicle is presented.A mechanically driven flapping rotary mechanism is designed to drive the three flapping wings and generate lift,and control mechanisms are designed to control the pose of the FWR-MAV.A flight control board for attitude control with robust onboard attitude estimation and a control algorithm is also developed to perform stable hovering flight and forward flight.A series of flight tests was conducted,with hovering flight and forward flight tests performed to optimize the control parameters and assess the performance of the FWR-MAV.The hovering flight test shows the ability of the FWR-MAV to counteract the moment generated by rotary motion and maintain the attitude of the FWR-MAV in space;the experiment of forward flight shows that the FWR-MAV can track the desired attitude.展开更多
The morphing wing can improve the flight performance during different phases.However,research has been subject to limitations in aerodynamic characteristics of the morphing wing with a flexible leading-edge.The comput...The morphing wing can improve the flight performance during different phases.However,research has been subject to limitations in aerodynamic characteristics of the morphing wing with a flexible leading-edge.The computational fluid dynamic method and dynamic mesh were used to simulate the continuous morphing of the flexible leading-edge.After comparing the steady aerodynamic characteristics of morphing and conventional wings,this study examined the unsteady aerodynamic characteristics of morphing wings with upward and downward deflections of the leading-edge at different frequencies.The numerical results show that for the steady aerodynamic,the leading-edge deflection mainly affects the stall characteristic.The downward deflection of the leading-edge increases the stall angle of attack and nose-down pitching moment.The results are opposite for the upward deflection.For the unsteady aerodynamic,at a small angle of attack,the transient lift coefficient of the upward deflection,growing with the increase of deflection frequency,is larger than that of the static case.The transient lift coefficient of the downward deflection,decreasing with the increase of deflection frequency,is smaller than that of the static case.However,at a large angle of attack,an opposite effect of deflection frequency on the transient lift coefficient was demonstrated.The transient lift coefficient is larger than that of the static case when the leading edge is in the nose-up stage,and lower than that of the static one in the nose-down stage.展开更多
To improve the survivability during an emergency situation, an algorithm for aircraft forced landing trajectory planning is proposed. The method integrates damaged aircraft modelling and trajectory planning into an op...To improve the survivability during an emergency situation, an algorithm for aircraft forced landing trajectory planning is proposed. The method integrates damaged aircraft modelling and trajectory planning into an optimal control framework, in order to deal with the complex aircraft flight dynamics, a solving strategy based on Gauss pseudospetral method (GPM) is presented. A 3-DOF nonlinear mass-point model taking into account the wind is developed to approximate the aircraft flight dynamics after loss of thrust. The solution minimizes the forced landing duration, with respect to the constraints that translate the changed dynamics, flight envelope limitation and operational safety requirements. The GPM is used to convert the trajectory planning problem to a nonlinear programming problem (NLP), which is solved by sequential quadratic programming algorithm. Simulation results show that the proposed algorithm can generate the minimum-time forced landing trajectory in event of engine-out with high efficiency and precision.展开更多
Design and implementation of an effective control mechanism is the key to enable the controlledflight of flapping wing rotor micro aerial vehicles(FWR-MAVs).In order to address this open challenge,in this paper,a trip...Design and implementation of an effective control mechanism is the key to enable the controlledflight of flapping wing rotor micro aerial vehicles(FWR-MAVs).In order to address this open challenge,in this paper,a triple-wing FWR-MAV with its particular control system is proposed.The corresponding experimental study of the vehicle is conducted.As a result,the triple-wing propulsion system demonstrates advantages in both lift generation and flight stability based on the force measurement.The control torques of the proposed FWR-MAV are generated by a particular slipflow rudder mechanism.The effectiveness of such a design combination has been validated experimentally.A series of flight tests are conducted,including sustained hovering and forward-backward maneuvering.To the best of our knowledge,such a design yields the world's first FWR-MAV capable of sustained controlled flight.展开更多
基金supported by the National Natural Science Foundation of China(11972059)。
文摘The robot pilot is a new concept of a robot system that pilots a manned aircraft,thereby forming a new type of unmanned aircraft system(UAS)that makes full use of the platform maturity,load capacity,and airworthiness of existing manned aircraft while greatly expanding the operation and application fields of UASs.In this research,the implementation and advantages of the robot pilot concept are discussed in detail,and a helicopter robot pilot is proposed to fly manned helicopters.The robot manipulators are designed according to the handling characteristics of the helicopter-controlling mechanism.Based on a kinematic analysis of the robot manipulators,a direct-driving method is established for the robot flight controller to reduce the time delay and control error of the robot servo process.A supporting ground station is built to realize different flight modes and the functional integration of the robot pilot.Finally,a prototype of the helicopter robot pilot is processed and installed in a helicopter to carry out flight tests.The test results show that the robot pilot can independently fly the helicopter to realize forward flight,backward flight,side flight,and turning flight,which verifies the effectiveness of the helicopter robot pilot.
基金Tsupported by the National Natural Science Foundation of China(11402014,11572023)the Royal Academy of Engineering for the project ‘‘Fast Nonlinear Aeroelastic Search for Loads Assessment’’(NCRP/1415/51)
文摘In this letter, a piezoaeroelastic energy harvester based on an airfoil with double plunge degrees of freedom is proposed to additionally take advantage of the vibrational energy of the airfoil pitch motion. An analytical model of the proposed energy harvesting system is built and compared with an equivalent model using the well-explored pitch-plunge configuration. The dynamic response and average power output of the harvester are numerically studied as the flow velocity exceeds the cut-in speed (flutter speed). It is found that the harvester with double-plunge configuration generates 4%-10% more power with varying flow velocities while reducing 670 of the cut-in speed than its counterpart.
基金This study was co-supported by the National Natural Science Foundation of China(No.T2288101)the National Key Research and Development Project,China(No.2020YFC1512500).
文摘The arresting process of carrier-based aircraft is widely recognized as a challenging task,characterized by the highest accident rate among all carrier-based aircraft operations.Dynamic simulation plays a crucial role in assessing the intricate responses of the arresting process,favoring the design of carrier-based aircraft.An efficient and accurate rigid-flexible coupling model for analyzing the dynamic response of the arresting process is proposed.By combining the dynamic characteristics of airframe,landing gear,arresting hook and arresting gear system,the rigid-flexible coupling dynamic model is established to reflect the relative motion of the coupling parts and arresting load.The dynamic model is verified through simulations of landing gear landing drops and by comparing the arresting simulation results with corresponding data in the US military standard.Additionally,simulations of the arresting process under different off-center distance and aircraft yaw angle are conducted to obtain the dynamic response of the aircraft during the arresting process.The result indicates that the rigid-flexible coupling dynamic model proposed is effective for analyzing the arresting dynamics response of carrier-based aircraft.The axial force of the arresting cable on both sides of the hook engagement point,pitch and yaw angle of aircraft are inconsistent under yaw and off-center arresting.The analysis method and obtained results provide valuable references for assessing the dynamic responses of carrier-based aircraft during arresting process and offer valuable in-sights in the design of carrier-based aircraft.
文摘“Ionic wind”generators are used as the main propulsion system in ion propulsion unmanned aerial vehicles(UAVs).Owing to the large size and poor stiffness of the electrode array in the propulsion system,the electrode array is prone to deformation under the flight load.In this work,the thrust characteristics and static aeroelastic properties of“ionic wind”propulsion systems were analyzed in detail.The simulation model for an“ionic wind”propulsion system was established by coupling a two-dimensional gas discharge model with a gas dynamics model.The influences of electrode voltage,spacing,size,and shape on the performance of the propulsion system were investigated.The fluid-solid interaction method was used to solve static aeroelastic characteristics under deformation.The aerodynamic and thrust performances of the elastic state and the rigid state were compared.It was found that the operating voltage,the distance between two electrodes,and the emitter radius had greater impacts on the thrust of the propulsion system.The propulsion system had a small contribution to the lift but a large contribution to the drag.In the elastic state,the lift coefficient accounted for 12.2%,and the drag coefficient accounted for 25.8%.Under the action of the downwash airflow from the wing,the propulsion system formed an upward moment around the center of mass,which contributed greatly to the pitching moment derivative of the whole aircraft.In the elastic state,the pitching moment derivative accounted for 29.7%.After elastic deformation,the thrust action point moved upward by 28.7 mm.Hence,the no lift pitching moment is reduced by 0.104 N$m,and the pitching moment coefficient is reduced by 0.014,causing a great impact on the longitudinal trimming of the whole aircraft.
基金supported by the National Natural Science Foundation of China(Nos.11402014 and 11572023).
文摘Morphing wings can improve aircraft performance during different flight phases.Recently research has focused on steady aerodynamic characteristics of the morphing wing with a flexible trailing-edge,and the unsteady aerodynamic and stall characteristics in the deflection process of the morphing wing are worthy further investigation.The effects of the angle of attack and deflection rate on aerodynamic characteristics were examined,and based on the aerodynamic characteristics of the morphing wing,a method was developed to delay stall by using the flexible periodic trailing-edge deflection.The numerical results show that the lift coefficients in the deflection process are smaller than those in the static situation at small angles of attack,and that the higher the deflection rate is,the smaller the lift coefficients will be.On the contrary,at large angles of attack,the lift coefficients are higher than those in the static case,and they become larger with the increase of the deflection rate.Further,the periodic deflection of the flexible trailing-edge with a small deflection amplitude and high deflection rate can increase lift coefficients at the critical stall angle.
基金Acknowledgment The authors would like to acknowledge the support of the National Natural Science Foundation of China (Nos. 11402014 and 11572023).
文摘Gliding is an important flight mode for insects because it saves energy during long distance flight without wing flapping. In this study, we investigated the influence of locust wing corrugation on the aerodynamic performance in gliding mode at low Reynolds number. Numerical simulations using two-dimensional Navier-Stokes equations are applied to study the gliding flight, which reveals the interaction between forewing and hindwing. The lift of the corrugated airfoil in a locust wing decreases from the wing root to the tip. Simulation results show that the pressure drags on the forewing and hindwing increase with an increase in wing thickness; while the lift-drag ratio of the airfoil is marginally affected by the corrugation on the airfoil. Geometric parameters analysis of the locust wing is also carried out, which includes the corrugation height, the corrugation placement and the shapes of leading and trailing edges.
基金supported by the National Natural Science Foundation of China(No.:11572023)。
文摘A three-wing Flapping Wing Rotor Micro Aerial Vehicle(FWR-MAV)which can perform controlled flight is introduced and an experimental study on this vehicle is presented.A mechanically driven flapping rotary mechanism is designed to drive the three flapping wings and generate lift,and control mechanisms are designed to control the pose of the FWR-MAV.A flight control board for attitude control with robust onboard attitude estimation and a control algorithm is also developed to perform stable hovering flight and forward flight.A series of flight tests was conducted,with hovering flight and forward flight tests performed to optimize the control parameters and assess the performance of the FWR-MAV.The hovering flight test shows the ability of the FWR-MAV to counteract the moment generated by rotary motion and maintain the attitude of the FWR-MAV in space;the experiment of forward flight shows that the FWR-MAV can track the desired attitude.
基金the Beijing Advanced Discipline Center for Unmanned Aircraft System。
文摘The morphing wing can improve the flight performance during different phases.However,research has been subject to limitations in aerodynamic characteristics of the morphing wing with a flexible leading-edge.The computational fluid dynamic method and dynamic mesh were used to simulate the continuous morphing of the flexible leading-edge.After comparing the steady aerodynamic characteristics of morphing and conventional wings,this study examined the unsteady aerodynamic characteristics of morphing wings with upward and downward deflections of the leading-edge at different frequencies.The numerical results show that for the steady aerodynamic,the leading-edge deflection mainly affects the stall characteristic.The downward deflection of the leading-edge increases the stall angle of attack and nose-down pitching moment.The results are opposite for the upward deflection.For the unsteady aerodynamic,at a small angle of attack,the transient lift coefficient of the upward deflection,growing with the increase of deflection frequency,is larger than that of the static case.The transient lift coefficient of the downward deflection,decreasing with the increase of deflection frequency,is smaller than that of the static case.However,at a large angle of attack,an opposite effect of deflection frequency on the transient lift coefficient was demonstrated.The transient lift coefficient is larger than that of the static case when the leading edge is in the nose-up stage,and lower than that of the static one in the nose-down stage.
基金supported by the National Key Basic Research Program of China(973 Program)(No.2011CB707002)
文摘To improve the survivability during an emergency situation, an algorithm for aircraft forced landing trajectory planning is proposed. The method integrates damaged aircraft modelling and trajectory planning into an optimal control framework, in order to deal with the complex aircraft flight dynamics, a solving strategy based on Gauss pseudospetral method (GPM) is presented. A 3-DOF nonlinear mass-point model taking into account the wind is developed to approximate the aircraft flight dynamics after loss of thrust. The solution minimizes the forced landing duration, with respect to the constraints that translate the changed dynamics, flight envelope limitation and operational safety requirements. The GPM is used to convert the trajectory planning problem to a nonlinear programming problem (NLP), which is solved by sequential quadratic programming algorithm. Simulation results show that the proposed algorithm can generate the minimum-time forced landing trajectory in event of engine-out with high efficiency and precision.
基金supported by the National Natural Science Foundation of China(No.11572023).
文摘Design and implementation of an effective control mechanism is the key to enable the controlledflight of flapping wing rotor micro aerial vehicles(FWR-MAVs).In order to address this open challenge,in this paper,a triple-wing FWR-MAV with its particular control system is proposed.The corresponding experimental study of the vehicle is conducted.As a result,the triple-wing propulsion system demonstrates advantages in both lift generation and flight stability based on the force measurement.The control torques of the proposed FWR-MAV are generated by a particular slipflow rudder mechanism.The effectiveness of such a design combination has been validated experimentally.A series of flight tests are conducted,including sustained hovering and forward-backward maneuvering.To the best of our knowledge,such a design yields the world's first FWR-MAV capable of sustained controlled flight.