Radiometer is a light-induced propulsive device in the rarefied gas environment,which holds great potential for next-gen near-space flight.However,its practical applications are hindered by the weak propulsion forces ...Radiometer is a light-induced propulsive device in the rarefied gas environment,which holds great potential for next-gen near-space flight.However,its practical applications are hindered by the weak propulsion forces produced on the conventional radiometer vanes.Herein,this crossdisciplinary study develops novel radiometer vanes with graphene aerogel coatings,which for the first time realize an order of magnitude enhancement in radiometric propulsion.The improvement is manifested as up to 29.7 times faster rotation speed at a low pressure of 0.2 Pa,13.8 times faster at the pressure(1.5 Pa)with maximum speeds,and 4 orders of magnitude broader operating pressure range(10^(-4)-10~2 Pa).Direct simulation Monte Carlo calculations reveal that the outstanding performance is ascribed to the improved temperature difference and gas-solid momentum transfer efficiency tailored by surface porous microstructures.Moreover,we demonstrate a stable and longterm levitation with the graphene aerogel-coated model in both 1 sun irradiation and a rarefied gas environment.展开更多
To establish the optimal reference trajectory for a near-space vehicle under free terminal time,a time-optimal model predictive static programming method is proposed with adaptive fish swarm optimization.First,the mod...To establish the optimal reference trajectory for a near-space vehicle under free terminal time,a time-optimal model predictive static programming method is proposed with adaptive fish swarm optimization.First,the model predictive static programming method is developed by incorporating neighboring terms and trust region,enabling rapid generation of precise optimal solutions.Next,an adaptive fish swarm optimization technique is employed to identify a sub-optimal solution,while a momentum gradient descent method with learning rate decay ensures the convergence to the global optimal solution.To validate the feasibility and accuracy of the proposed method,a near-space vehicle example is analyzed and simulated during its glide phase.The simulation results demonstrate that the proposed method aligns with theoretical derivations and outperforms existing methods in terms of convergence speed and accuracy.Therefore,the proposed method offers significant practical value for solving the fast trajectory optimization problem in near-space vehicle applications.展开更多
A novel nonlinear adaptive control method is presented for a near-space hypersonic vehicle （NHV） in the presence of strong uncertainties and disturbances. The control law consists of the optimal generalized predicti...A novel nonlinear adaptive control method is presented for a near-space hypersonic vehicle （NHV） in the presence of strong uncertainties and disturbances. The control law consists of the optimal generalized predictive controller （OGPC） and the functional link network （FLN） direct adaptive law. OGPC is a continuous-time nonlinear predictive control law. The FLN adaptive law is used to offset the unknown uncertainties and disturbances in a flight through the online learning. The learning process does not need any offline training phase. The stability analyses of the NHV close-loop system are provided and it is proved that the system error and the weight learning error are uniformly ultimately hounded. Simulation results show the satisfactory performance of the con- troller for the attitude tracking.展开更多
The design of optimal guidance law for intercepting a near-space hypersonic maneuvering target with bounded inputs is considered. Firstly, a maneuvering model for near-space hypersonic aircraft is given. Then, the air...The design of optimal guidance law for intercepting a near-space hypersonic maneuvering target with bounded inputs is considered. Firstly, a maneuvering model for near-space hypersonic aircraft is given. Then, the aircraft acceleration prediction can be obtained using this model with two neural networks. By using the target acceleration prediction, which is taken into account when calculating the Zero Effort Miss(ZEM), an optimal sliding-mode guidance law is proposed to fulfill the guidance task. An adaptive sliding-mode switch term is designed to deal with actuator saturation and prediction errors. Finally, numerical simulations show that the proposed guidance law can reduce the energy consumption and the terminal acceleration command of the interceptor effectively.展开更多
The control law design for a near-space hypersonic vehicle(NHV)is highly challenging due to its inherent nonlinearity,plant uncertainties and sensitivity to disturbances.This paper presents a novel functional link net...The control law design for a near-space hypersonic vehicle(NHV)is highly challenging due to its inherent nonlinearity,plant uncertainties and sensitivity to disturbances.This paper presents a novel functional link network(FLN)control method for an NHV with dynamical thrust and parameter uncertainties.The approach devises a new partially-feedback-functional-link-network(PFFLN)adaptive law and combines it with the nonlinear generalized predictive control(NGPC)algorithm.The PFFLN is employed for approximating uncertainties in flight.Its weights are online tuned based on Lyapunov stability theorem for the first time.The learning process does not need any offline training phase.Additionally,a robust controller with an adaptive gain is designed to offset the approximation error.Finally,simulation results show a satisfactory performance for the NHV attitude tracking,and also illustrate the controller's robustness.展开更多
Near-space airship is a frontier and hotspot in current military research and development,and the near-space composite propeller is the key technology for its development.In order to obtain higher aerodynamic efficien...Near-space airship is a frontier and hotspot in current military research and development,and the near-space composite propeller is the key technology for its development.In order to obtain higher aerodynamic efficiency at an altitude of 22 km,a certain near-space composite propeller is designed as a long and slender aerodynamic shape with a 10 m diameter,which brings many challenges to the composite structure design.The initial design is obtained by the composite structure variable stiffness design method using based on fixed region division blending model.However,it weighs 23.142 kg,exceeding the required 20 kg.In order to meet the structural design requirements of the propeller,a variable stiffness design method using the adaptive region division blending model is proposed in this paper.Compared with the methods using the fixed region division blending model,this method optimizes region division,stacking thickness and stacking sequence in a single level,considering the coupling effect among them.Through a more refined region division,this method can provide a more optimal design for composite tapered structures.Additionally,to improve the efficiency of optimization subjected to manufacturing constraints,a hierarchical penalty function is proposed to quickly filter out the solutions that do not meet manufacturing constraints.The above methods combined with a Genetic Algorithm(GA)using specific encoding are adopted to optimize the near-space composite propeller.The optimal design of the structure weighs 18.831 kg,with all manufacturing constraints and all structural response constraints being satisfied.Compared with the initial design,the optimal design has a more refined region division,and achieves a weight reduction of 18.6%.This demonstrates that a refined region division can significantly improve the mechanical performance of the composite tapered structure.展开更多
It is an important scientific research activity in China to carry out near-space exploration and scientific experiments via aerospace carriers.Early near-space exploration projects mainly used aircraft,balloons,soundi...It is an important scientific research activity in China to carry out near-space exploration and scientific experiments via aerospace carriers.Early near-space exploration projects mainly used aircraft,balloons,sounding rockets and Earth satellites to carry out space environment exploration.With the development of China’s space science and technology,microgravity science has become a frontier science that has developed rapidly in the past 20 years.With the continuous progress of national space science and technology,the demand for near-space exploration and scientific experiments is increasing year by year.In the next 2 to 3 years,many advanced science activities and the associated technologies need to conduct corresponding experimental research work.This paper mainly analyzes the significance of scientific research and the ways to realize near-space exploration at home and abroad,and analyzes the directions and innovations that can be carried out in the future.展开更多
At present,near-space aerostats lack lateral flight control capabilities and can only perform long-range detour flights by adjusting flight altitude and utilizing existing wind field conditions.Their flight trajectori...At present,near-space aerostats lack lateral flight control capabilities and can only perform long-range detour flights by adjusting flight altitude and utilizing existing wind field conditions.Their flight trajectories and station-keeping radii are difficult to regulate,which greatly restricts their application prospects.In this paper,a technical scheme for a low-power near-space aerostat is proposed.A novel lateral propulsion system and thrust vector control system are designed,significantly improving the trajectory planning and station-keeping capabilities of the aerostat.This paper introduced the system composition,working principle,and flight control strategies of the new aerostat.Computational fluid dynamics simulations were conducted to analyze propeller aerodynamic performance under various operating conditions.The propeller aerodynamic performance under various operating conditions was analyzed,and the impact of rotational speed on propeller thrust,torque,and power consumption was investigated.A dynamics model was established and integrated with historical wind field data to simulate trajectories the trajectory simulation results of the aerostat under different control strategies were obtained.Simulation results demonstrated that the low-power lateral propulsion system can effectively improve the station-keeping capability and trajectory planning capability of the aerostat.展开更多
Near-space hypersonic unmanned aircrafts(NHUA)encounter significant aerodynamic heating effects when flying at high velocities in extreme conditions.This leads to the generation of extremely high temperatures,reaching...Near-space hypersonic unmanned aircrafts(NHUA)encounter significant aerodynamic heating effects when flying at high velocities in extreme conditions.This leads to the generation of extremely high temperatures,reaching several thousand degrees,posing a substantial risk to the safety of NHUA.Accurate and rapid prediction of the aerothermodynamic environment is crucial for the thermal protection of NHUA.Conventional approaches exhibit some limitations,including the need for extensive pre-processing,long calculation time,inadequate precision,and reliance on expert knowledge,making them ill-suited for online intelligent prediction.This study proposes a novel“flying state-pressure and heat flux-temperature”data-driven prediction theoretical framework,considering both efficiency and accuracy.Our approach entails a prediction model for high-dimensional pressure and heat flux fields,employing principal component analysis(PCA)and multi-layer perceptron(MLP)models.A temperature time series model is also constructed using recurrent neural networks(RNN).The experimental results suggest that the prediction error falls within a narrow margin of approximately 5%.It takes around 0.1 seconds to forecast a high-dimensional field and 1 second to predict the temperature time series,which satisfies both speed and accuracy requirements.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51902009 and 12272028)the Fundamental Research Funds for the Central Universities,“Zhuoyue 100”Talent Program,China。
文摘Radiometer is a light-induced propulsive device in the rarefied gas environment,which holds great potential for next-gen near-space flight.However,its practical applications are hindered by the weak propulsion forces produced on the conventional radiometer vanes.Herein,this crossdisciplinary study develops novel radiometer vanes with graphene aerogel coatings,which for the first time realize an order of magnitude enhancement in radiometric propulsion.The improvement is manifested as up to 29.7 times faster rotation speed at a low pressure of 0.2 Pa,13.8 times faster at the pressure(1.5 Pa)with maximum speeds,and 4 orders of magnitude broader operating pressure range(10^(-4)-10~2 Pa).Direct simulation Monte Carlo calculations reveal that the outstanding performance is ascribed to the improved temperature difference and gas-solid momentum transfer efficiency tailored by surface porous microstructures.Moreover,we demonstrate a stable and longterm levitation with the graphene aerogel-coated model in both 1 sun irradiation and a rarefied gas environment.
基金supported by the National Science Foundation for Distinguished Young Scholars of China(No.52425212)National Key Research and Development Program of China(No.2021YFA0717100)National Natural Science Foundation of China(Nos.12072270,U2013206,and 52442214).
文摘To establish the optimal reference trajectory for a near-space vehicle under free terminal time,a time-optimal model predictive static programming method is proposed with adaptive fish swarm optimization.First,the model predictive static programming method is developed by incorporating neighboring terms and trust region,enabling rapid generation of precise optimal solutions.Next,an adaptive fish swarm optimization technique is employed to identify a sub-optimal solution,while a momentum gradient descent method with learning rate decay ensures the convergence to the global optimal solution.To validate the feasibility and accuracy of the proposed method,a near-space vehicle example is analyzed and simulated during its glide phase.The simulation results demonstrate that the proposed method aligns with theoretical derivations and outperforms existing methods in terms of convergence speed and accuracy.Therefore,the proposed method offers significant practical value for solving the fast trajectory optimization problem in near-space vehicle applications.
基金Supported by the National Nature Science Foundation of China (90716028)~~
文摘A novel nonlinear adaptive control method is presented for a near-space hypersonic vehicle （NHV） in the presence of strong uncertainties and disturbances. The control law consists of the optimal generalized predictive controller （OGPC） and the functional link network （FLN） direct adaptive law. OGPC is a continuous-time nonlinear predictive control law. The FLN adaptive law is used to offset the unknown uncertainties and disturbances in a flight through the online learning. The learning process does not need any offline training phase. The stability analyses of the NHV close-loop system are provided and it is proved that the system error and the weight learning error are uniformly ultimately hounded. Simulation results show the satisfactory performance of the con- troller for the attitude tracking.
基金supported by the National Natural Science Foundation of China(No.61773142)。
文摘The design of optimal guidance law for intercepting a near-space hypersonic maneuvering target with bounded inputs is considered. Firstly, a maneuvering model for near-space hypersonic aircraft is given. Then, the aircraft acceleration prediction can be obtained using this model with two neural networks. By using the target acceleration prediction, which is taken into account when calculating the Zero Effort Miss(ZEM), an optimal sliding-mode guidance law is proposed to fulfill the guidance task. An adaptive sliding-mode switch term is designed to deal with actuator saturation and prediction errors. Finally, numerical simulations show that the proposed guidance law can reduce the energy consumption and the terminal acceleration command of the interceptor effectively.
基金supported by the National Natural Science Foundation of China(9071602860974106)
文摘The control law design for a near-space hypersonic vehicle(NHV)is highly challenging due to its inherent nonlinearity,plant uncertainties and sensitivity to disturbances.This paper presents a novel functional link network(FLN)control method for an NHV with dynamical thrust and parameter uncertainties.The approach devises a new partially-feedback-functional-link-network(PFFLN)adaptive law and combines it with the nonlinear generalized predictive control(NGPC)algorithm.The PFFLN is employed for approximating uncertainties in flight.Its weights are online tuned based on Lyapunov stability theorem for the first time.The learning process does not need any offline training phase.Additionally,a robust controller with an adaptive gain is designed to offset the approximation error.Finally,simulation results show a satisfactory performance for the NHV attitude tracking,and also illustrate the controller's robustness.
基金This study was co-supported by stable funding from the National Key Laboratory of Aerofoil and Grille Aerodynamics,China.
文摘Near-space airship is a frontier and hotspot in current military research and development,and the near-space composite propeller is the key technology for its development.In order to obtain higher aerodynamic efficiency at an altitude of 22 km,a certain near-space composite propeller is designed as a long and slender aerodynamic shape with a 10 m diameter,which brings many challenges to the composite structure design.The initial design is obtained by the composite structure variable stiffness design method using based on fixed region division blending model.However,it weighs 23.142 kg,exceeding the required 20 kg.In order to meet the structural design requirements of the propeller,a variable stiffness design method using the adaptive region division blending model is proposed in this paper.Compared with the methods using the fixed region division blending model,this method optimizes region division,stacking thickness and stacking sequence in a single level,considering the coupling effect among them.Through a more refined region division,this method can provide a more optimal design for composite tapered structures.Additionally,to improve the efficiency of optimization subjected to manufacturing constraints,a hierarchical penalty function is proposed to quickly filter out the solutions that do not meet manufacturing constraints.The above methods combined with a Genetic Algorithm(GA)using specific encoding are adopted to optimize the near-space composite propeller.The optimal design of the structure weighs 18.831 kg,with all manufacturing constraints and all structural response constraints being satisfied.Compared with the initial design,the optimal design has a more refined region division,and achieves a weight reduction of 18.6%.This demonstrates that a refined region division can significantly improve the mechanical performance of the composite tapered structure.
文摘It is an important scientific research activity in China to carry out near-space exploration and scientific experiments via aerospace carriers.Early near-space exploration projects mainly used aircraft,balloons,sounding rockets and Earth satellites to carry out space environment exploration.With the development of China’s space science and technology,microgravity science has become a frontier science that has developed rapidly in the past 20 years.With the continuous progress of national space science and technology,the demand for near-space exploration and scientific experiments is increasing year by year.In the next 2 to 3 years,many advanced science activities and the associated technologies need to conduct corresponding experimental research work.This paper mainly analyzes the significance of scientific research and the ways to realize near-space exploration at home and abroad,and analyzes the directions and innovations that can be carried out in the future.
基金supported by the National Natural Science Foundation of China(Grant No:12572399)Hainan Provincial Natural Science Foundation of China(Grant No:523MS115)the National Key Research and Development Program of China(Grant No:2022YFB390180502,2022YFB3901805).
文摘At present,near-space aerostats lack lateral flight control capabilities and can only perform long-range detour flights by adjusting flight altitude and utilizing existing wind field conditions.Their flight trajectories and station-keeping radii are difficult to regulate,which greatly restricts their application prospects.In this paper,a technical scheme for a low-power near-space aerostat is proposed.A novel lateral propulsion system and thrust vector control system are designed,significantly improving the trajectory planning and station-keeping capabilities of the aerostat.This paper introduced the system composition,working principle,and flight control strategies of the new aerostat.Computational fluid dynamics simulations were conducted to analyze propeller aerodynamic performance under various operating conditions.The propeller aerodynamic performance under various operating conditions was analyzed,and the impact of rotational speed on propeller thrust,torque,and power consumption was investigated.A dynamics model was established and integrated with historical wind field data to simulate trajectories the trajectory simulation results of the aerostat under different control strategies were obtained.Simulation results demonstrated that the low-power lateral propulsion system can effectively improve the station-keeping capability and trajectory planning capability of the aerostat.
基金supported by the National Natural Science Foundation of China(No.72301153).
文摘Near-space hypersonic unmanned aircrafts(NHUA)encounter significant aerodynamic heating effects when flying at high velocities in extreme conditions.This leads to the generation of extremely high temperatures,reaching several thousand degrees,posing a substantial risk to the safety of NHUA.Accurate and rapid prediction of the aerothermodynamic environment is crucial for the thermal protection of NHUA.Conventional approaches exhibit some limitations,including the need for extensive pre-processing,long calculation time,inadequate precision,and reliance on expert knowledge,making them ill-suited for online intelligent prediction.This study proposes a novel“flying state-pressure and heat flux-temperature”data-driven prediction theoretical framework,considering both efficiency and accuracy.Our approach entails a prediction model for high-dimensional pressure and heat flux fields,employing principal component analysis(PCA)and multi-layer perceptron(MLP)models.A temperature time series model is also constructed using recurrent neural networks(RNN).The experimental results suggest that the prediction error falls within a narrow margin of approximately 5%.It takes around 0.1 seconds to forecast a high-dimensional field and 1 second to predict the temperature time series,which satisfies both speed and accuracy requirements.
