Aiming at the complex tilting process of quad tilt-rotor(QTR)transition mode,this paper studies the manipulation strategy in transition mode to solve the problem of manipulation redundancy and coupling in transition m...Aiming at the complex tilting process of quad tilt-rotor(QTR)transition mode,this paper studies the manipulation strategy in transition mode to solve the problem of manipulation redundancy and coupling in transition mode of quad tilt rotor.The variations of the manipulation derivative are analyzed in the tilting process.Through the flight control simulation and flight test of the quad tilt-rotor,the validity of the control system and the rationality of the manipulation strategy are verified.展开更多
A morphing aircraft can adapt its configuration to suit different types of tasks,which is also an important requirement of Unmanned Aerial Vehicles(UAV).The successful development of an unmanned morphing aircraft invo...A morphing aircraft can adapt its configuration to suit different types of tasks,which is also an important requirement of Unmanned Aerial Vehicles(UAV).The successful development of an unmanned morphing aircraft involves three steps that determine its ability and intelligent:configuration design,dynamic modeling and flight control.This study conducts a comprehensive survey of morphing aircraft.First,the methods to design the configuration of a morphing aircraft are presented and analyzed.Then,the nonlinear dynamic characteristics and aerodynamic interference caused by a morphing wing are described.Subsequently,the dynamic modeling and flight control methods for solving the flight control problems are summarized with respect to these features.Finally,the general as well as special challenges ahead of the development of intelligent morphing aircraft are discussed.The findings can provide a theoretical and technical reference for designing future morphing aircraft or morphing-wing UAVs.展开更多
The composite leaf spring landing gear of an electric aircraft is optimized.With the strength and workability as constraints and the minimum structural weight as an objective,the two-stage optimization of the leaf spr...The composite leaf spring landing gear of an electric aircraft is optimized.With the strength and workability as constraints and the minimum structural weight as an objective,the two-stage optimization of the leaf spring landing gear with glass fiber unidirectional prepreg is carried out using a genetic algorithm,namely,the optimization of continuous thickness of layup,and the optimization of the layup sequence and discrete thickness.In the optimization process,the ground loads are calculated according to the structural stiffness of each chromosome,thus the stiffness constraints are relaxed,and the optimization results are compared with those using stiffness constraints.The static experiment verification reveals that the numerical simulation and experimental results are consistent,that is,the optimized leaf spring meets the strength requirements.The results show that the leaf spring landing gear based on two-stage optimization method achieves the objective of weight reduction.展开更多
The aerodynamic model of propeller,wing,fuselage and vertical tail are established for the tilt quad rotor(TQR)with partial tilt-wing,and then the flight dynamic model is established.Based on the six-degree-of-freedom...The aerodynamic model of propeller,wing,fuselage and vertical tail are established for the tilt quad rotor(TQR)with partial tilt-wing,and then the flight dynamic model is established.Based on the six-degree-of-freedom equation and the small disturbance linearization assumption,the trimming and stability of the tilt quad rotor with partial tilt-wing and the tilt quad rotor without tilt-wing are analyzed.The results show that in the hovering state,due to the existence of tilt-wing,the propeller wake reduces the downwash on the wing,thereby reducing the vertical weight gain of the aircraft.It is beneficial to increase the endurance time and improve the endurance performance.The transition corridor of the TQR with tilt-wing is narrower than that of the TQR without tilt-wing,but the transition corridor of TQR with tilt-wing still has a large space for design.Furthermore,the stability analysis shows that the Dutch roll damping ratio is larger,and in other modes the aircraft has a certain stability.The manipulation response analysis shows that in the transition mode the lateral-directional coupling is strong.展开更多
An unsteady load calculation method for the support configuration of a monopile-supported offshore wind turbine is developed based on the Fluent software platform.Firstly,the water wave is generated by imposing the in...An unsteady load calculation method for the support configuration of a monopile-supported offshore wind turbine is developed based on the Fluent software platform.Firstly,the water wave is generated by imposing the inlet boundary conditions according to the exact potential flow solution.Then the wave evolution is simulated by solving the unsteady incompressible Navier-Stokes(N-S)equations coupled with the volume of fluid method.For the small amplitude wave with reasonable wave parameters,the numerical wave result agrees well with that of the given wave model.Finally,a monopile support configuration is introduced and a CFD-based load calculation method is established to accurately calculate the unsteady load under the combined action of wave and wind.The computed unsteady wave load on a small-size monopile support located in the small amplitude wave flow coincides with that of the Morison formula.The load calculations are also performed on a large-size monopile support and a monopile-supported offshore wind turbine under the combined action of small amplitude wave and wind.展开更多
Due to the portability and anti-interference ability,vision-based shipborne aircraft automatic landing systems have attracted the attention of researchers.In this paper,a Monocular Camera and Laser Range Finder(MC-LRF...Due to the portability and anti-interference ability,vision-based shipborne aircraft automatic landing systems have attracted the attention of researchers.In this paper,a Monocular Camera and Laser Range Finder(MC-LRF)-based pose measurement system is designed for shipborne aircraft automatic landing.First,the system represents the target ship using a set of sparse landmarks,and a two-stage model is adopted to detect landmarks on the target ship.The rough 6D pose is measured by solving a Perspective-n-Point problem.Then,once the rough pose is measured,a region-based pose refinement is used to continuously track the 6D pose in the subsequent image sequences.To address the low accuracy of monocular pose measurement in the depth direction,the designed system adopts a laser range finder to obtain an accurate range value.The measured rough pose is iteratively optimized using the accurate range measurement.Experimental results on synthetic and real images show that the system achieves robust and precise pose measurement of the target ship during automatic landing.The measurement means error is within 0.4in rotation,and 0.2%in translation,meeting the requirements for automatic fixed-wing aircraft landing.展开更多
Reinforcement Learning(RL)algorithms enhance intelligence of air combat AutonomousManeuver Decision(AMD)policy,but they may underperform in target combat environmentswith disturbances.To enhance the robustness of the ...Reinforcement Learning(RL)algorithms enhance intelligence of air combat AutonomousManeuver Decision(AMD)policy,but they may underperform in target combat environmentswith disturbances.To enhance the robustness of the AMD strategy learned by RL,thisstudy proposes a Tube-based Robust RL(TRRL)method.First,this study introduces a tube todescribe reachable trajectories under disturbances,formulates a method for calculating tubes basedon sum-of-squares programming,and proposes the TRRL algorithm that enhances robustness byutilizing tube size as a quantitative indicator.Second,this study introduces offline techniques forregressing the tube size function and establishing a tube library before policy learning,aiming toeliminate complex online tube solving and reduce the computational burden during training.Furthermore,an analysis of the tube library demonstrates that the mitigated AMD strategy achievesgreater robustness,as smaller tube sizes correspond to more cautious actions.This finding highlightsthat TRRL enhances robustness by promoting a conservative policy.To effectively balanceaggressiveness and robustness,the proposed TRRL algorithm introduces a“laziness factor”as aweight of robustness.Finally,combat simulations in an environment with disturbances confirm thatthe AMD policy learned by the TRRL algorithm exhibits superior air combat performance comparedto selected robust RL baselines.展开更多
With the explosive development of aerospace science,the design of the new generation airliner at higher speeds is attracting more attentions.To achieve this goal,it is necessary to achieve accurate prediction of the a...With the explosive development of aerospace science,the design of the new generation airliner at higher speeds is attracting more attentions.To achieve this goal,it is necessary to achieve accurate prediction of the aerodynamic heating/force loads and successful reduction of drag and heat flux.As a remedy for the existing studies which are based upon the CFD and wind tunnel tests,this study presents a flight test for the drag and heat reduction spike technology.The principal goals of this flight test were to provide reference for verifying the accuracy of the prediction technology on ground and promote the development of the drag and heat reduction technology.By adopting the OS-X rocket,the TT-0 test vehicle designed by Shenyang Aircraft Design&Research Institute reached a maximum Mach number of 5.8 and a maximum altitude of 38 km.Hypersonic and supersonic pressure data by pressure scanning valves and heat fluxes by gauges at different locations were obtained successfully.Also,heat fluxes obtained by in-house CFD code are illustrated in comparison with the flight data.The results indicate that the numerical errors are large in most cases.More technologies,such as more CFD codes and more numerical procedures,should be adopted to conduct studies on this issue in the future.展开更多
Precise calculation of the trajectory of store separation is critical in assess-ing whether the store can be released safely.Store ejection is the initial stage of the releasing process and any uncertainty introduced ...Precise calculation of the trajectory of store separation is critical in assess-ing whether the store can be released safely.Store ejection is the initial stage of the releasing process and any uncertainty introduced at this stage will propagate through the whole trajectory.In this work,the impact of the uncertainties in ejector modeling on the simulation of a generic store separation is investigated by using a Monte-Carlo-based approach.To reduce the extremely large computation cost resulted from the direct use CFD in Monte Carlo simulation,the CFD solutions are represented by a time-dependent Kriging model,which is constructed at each time step by using the samples from the URANS simulations.The stochastic outputs,including the distri-bution of probability density function,expected value and 95%confidence interval of store separation trajectory,are obtained by the Monte Carlo simulations.The sensitiv-ity analysis is also carried out by using the Monte-Carlo-based method to determine the most significant variables in ejector modeling,which affect the output uncertainty.Our results show that ejector modeling is one of the main uncertainty sources of store separation simulation and the approximation in ejector modeling can cause a signifi-cant deviation,especially in the angular displacement.展开更多
基金supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘Aiming at the complex tilting process of quad tilt-rotor(QTR)transition mode,this paper studies the manipulation strategy in transition mode to solve the problem of manipulation redundancy and coupling in transition mode of quad tilt rotor.The variations of the manipulation derivative are analyzed in the tilting process.Through the flight control simulation and flight test of the quad tilt-rotor,the validity of the control system and the rationality of the manipulation strategy are verified.
基金supported by the National Key R&D Program of China(No.2018YFC0810102)the National Natural Science Foundation of China(Nos.91848203 and 91948202)+1 种基金the State Key Laboratory of Robotics(2020-Z02)Natural Science Foundation of Liao Ning Province of China(20180520014)。
文摘A morphing aircraft can adapt its configuration to suit different types of tasks,which is also an important requirement of Unmanned Aerial Vehicles(UAV).The successful development of an unmanned morphing aircraft involves three steps that determine its ability and intelligent:configuration design,dynamic modeling and flight control.This study conducts a comprehensive survey of morphing aircraft.First,the methods to design the configuration of a morphing aircraft are presented and analyzed.Then,the nonlinear dynamic characteristics and aerodynamic interference caused by a morphing wing are described.Subsequently,the dynamic modeling and flight control methods for solving the flight control problems are summarized with respect to these features.Finally,the general as well as special challenges ahead of the development of intelligent morphing aircraft are discussed.The findings can provide a theoretical and technical reference for designing future morphing aircraft or morphing-wing UAVs.
基金the Natural Science Foundation of Liaoning (No. 20180550824)。
文摘The composite leaf spring landing gear of an electric aircraft is optimized.With the strength and workability as constraints and the minimum structural weight as an objective,the two-stage optimization of the leaf spring landing gear with glass fiber unidirectional prepreg is carried out using a genetic algorithm,namely,the optimization of continuous thickness of layup,and the optimization of the layup sequence and discrete thickness.In the optimization process,the ground loads are calculated according to the structural stiffness of each chromosome,thus the stiffness constraints are relaxed,and the optimization results are compared with those using stiffness constraints.The static experiment verification reveals that the numerical simulation and experimental results are consistent,that is,the optimized leaf spring meets the strength requirements.The results show that the leaf spring landing gear based on two-stage optimization method achieves the objective of weight reduction.
基金supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
文摘The aerodynamic model of propeller,wing,fuselage and vertical tail are established for the tilt quad rotor(TQR)with partial tilt-wing,and then the flight dynamic model is established.Based on the six-degree-of-freedom equation and the small disturbance linearization assumption,the trimming and stability of the tilt quad rotor with partial tilt-wing and the tilt quad rotor without tilt-wing are analyzed.The results show that in the hovering state,due to the existence of tilt-wing,the propeller wake reduces the downwash on the wing,thereby reducing the vertical weight gain of the aircraft.It is beneficial to increase the endurance time and improve the endurance performance.The transition corridor of the TQR with tilt-wing is narrower than that of the TQR without tilt-wing,but the transition corridor of TQR with tilt-wing still has a large space for design.Furthermore,the stability analysis shows that the Dutch roll damping ratio is larger,and in other modes the aircraft has a certain stability.The manipulation response analysis shows that in the transition mode the lateral-directional coupling is strong.
基金supported partly by the National Basic Research Program of China("973"Program)(No.2014CB046200)the National Natural Science Foundation of China(No.11372135)the NUAA Fundamental Research Funds(No.NS2013005)
文摘An unsteady load calculation method for the support configuration of a monopile-supported offshore wind turbine is developed based on the Fluent software platform.Firstly,the water wave is generated by imposing the inlet boundary conditions according to the exact potential flow solution.Then the wave evolution is simulated by solving the unsteady incompressible Navier-Stokes(N-S)equations coupled with the volume of fluid method.For the small amplitude wave with reasonable wave parameters,the numerical wave result agrees well with that of the given wave model.Finally,a monopile support configuration is introduced and a CFD-based load calculation method is established to accurately calculate the unsteady load under the combined action of wave and wind.The computed unsteady wave load on a small-size monopile support located in the small amplitude wave flow coincides with that of the Morison formula.The load calculations are also performed on a large-size monopile support and a monopile-supported offshore wind turbine under the combined action of small amplitude wave and wind.
基金co-supported by the National Natural Science Foundation of China,China(No.12272404)the Postgraduate Research Innovation Project of Hunan Province of China,China(No.CX20210016).
文摘Due to the portability and anti-interference ability,vision-based shipborne aircraft automatic landing systems have attracted the attention of researchers.In this paper,a Monocular Camera and Laser Range Finder(MC-LRF)-based pose measurement system is designed for shipborne aircraft automatic landing.First,the system represents the target ship using a set of sparse landmarks,and a two-stage model is adopted to detect landmarks on the target ship.The rough 6D pose is measured by solving a Perspective-n-Point problem.Then,once the rough pose is measured,a region-based pose refinement is used to continuously track the 6D pose in the subsequent image sequences.To address the low accuracy of monocular pose measurement in the depth direction,the designed system adopts a laser range finder to obtain an accurate range value.The measured rough pose is iteratively optimized using the accurate range measurement.Experimental results on synthetic and real images show that the system achieves robust and precise pose measurement of the target ship during automatic landing.The measurement means error is within 0.4in rotation,and 0.2%in translation,meeting the requirements for automatic fixed-wing aircraft landing.
文摘Reinforcement Learning(RL)algorithms enhance intelligence of air combat AutonomousManeuver Decision(AMD)policy,but they may underperform in target combat environmentswith disturbances.To enhance the robustness of the AMD strategy learned by RL,thisstudy proposes a Tube-based Robust RL(TRRL)method.First,this study introduces a tube todescribe reachable trajectories under disturbances,formulates a method for calculating tubes basedon sum-of-squares programming,and proposes the TRRL algorithm that enhances robustness byutilizing tube size as a quantitative indicator.Second,this study introduces offline techniques forregressing the tube size function and establishing a tube library before policy learning,aiming toeliminate complex online tube solving and reduce the computational burden during training.Furthermore,an analysis of the tube library demonstrates that the mitigated AMD strategy achievesgreater robustness,as smaller tube sizes correspond to more cautious actions.This finding highlightsthat TRRL enhances robustness by promoting a conservative policy.To effectively balanceaggressiveness and robustness,the proposed TRRL algorithm introduces a“laziness factor”as aweight of robustness.Finally,combat simulations in an environment with disturbances confirm thatthe AMD policy learned by the TRRL algorithm exhibits superior air combat performance comparedto selected robust RL baselines.
基金co-supported by National Natural Science Foundation of China(Nos.11902265 and 11972308)Natural Science Foundation of Shaanxi Province of China(No.2019JQ-376)the Fundamental Research Funds for the Central Universities of China(Nos.G2018KY0304 and G2018KY0308)。
文摘With the explosive development of aerospace science,the design of the new generation airliner at higher speeds is attracting more attentions.To achieve this goal,it is necessary to achieve accurate prediction of the aerodynamic heating/force loads and successful reduction of drag and heat flux.As a remedy for the existing studies which are based upon the CFD and wind tunnel tests,this study presents a flight test for the drag and heat reduction spike technology.The principal goals of this flight test were to provide reference for verifying the accuracy of the prediction technology on ground and promote the development of the drag and heat reduction technology.By adopting the OS-X rocket,the TT-0 test vehicle designed by Shenyang Aircraft Design&Research Institute reached a maximum Mach number of 5.8 and a maximum altitude of 38 km.Hypersonic and supersonic pressure data by pressure scanning valves and heat fluxes by gauges at different locations were obtained successfully.Also,heat fluxes obtained by in-house CFD code are illustrated in comparison with the flight data.The results indicate that the numerical errors are large in most cases.More technologies,such as more CFD codes and more numerical procedures,should be adopted to conduct studies on this issue in the future.
基金The work was financially supported by National Numerical Windtunnel(Grant No.NNW2019ZT7-B31)This research was also supported in part by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Precise calculation of the trajectory of store separation is critical in assess-ing whether the store can be released safely.Store ejection is the initial stage of the releasing process and any uncertainty introduced at this stage will propagate through the whole trajectory.In this work,the impact of the uncertainties in ejector modeling on the simulation of a generic store separation is investigated by using a Monte-Carlo-based approach.To reduce the extremely large computation cost resulted from the direct use CFD in Monte Carlo simulation,the CFD solutions are represented by a time-dependent Kriging model,which is constructed at each time step by using the samples from the URANS simulations.The stochastic outputs,including the distri-bution of probability density function,expected value and 95%confidence interval of store separation trajectory,are obtained by the Monte Carlo simulations.The sensitiv-ity analysis is also carried out by using the Monte-Carlo-based method to determine the most significant variables in ejector modeling,which affect the output uncertainty.Our results show that ejector modeling is one of the main uncertainty sources of store separation simulation and the approximation in ejector modeling can cause a signifi-cant deviation,especially in the angular displacement.
