During the process of aircraft design, the mathematical model of pilot control behavior characteristics is always used to predict aircraft flying qualities （FQ）. This is one of the important methods to avoid pilot-a...During the process of aircraft design, the mathematical model of pilot control behavior characteristics is always used to predict aircraft flying qualities （FQ）. This is one of the important methods to avoid pilot-aircraft adverse coupling. In order to study the FQ criterion based on closed-loop pilot-aircraft systems, first, an experimental database is built, which includes 40 aircraft dynamics configurations and the corresponding flight simulation results. Second, the mathematical pilot models with a set of different aircraft configurations are obtained by this experimental database. Then, two FQ criteria, Neal-Smith criterion and Moscow Aviation Institute （MAI） criterion, are analyzed. And the relationship between the FQ level evaluated by actual pilot and the parameters of closed-loop pilot-aircraft systems is studied. Finally, an improved criterion of aircraft FQ is built based on the above two criteria. This new criterion is further used to predict FQ for four new aircraft dynamics configurations, and the prediction results verify its accuracy and practicability.展开更多
Unmanned Aircraft Systems(UASs) have advanced technologically and surged exponentially over recent years. Currently, due to safety concerns, most civil operations of UAS are conducted in low-level uncontrolled area or...Unmanned Aircraft Systems(UASs) have advanced technologically and surged exponentially over recent years. Currently, due to safety concerns, most civil operations of UAS are conducted in low-level uncontrolled area or in segregated controlled airspace. As the industry progresses, both operational and technological capabilities have matured to the point where UASs are expected to gain greater freedom of access to both controlled and uncontrolled airspace. Extensive technical and regulatory surveys have been conducted to enable the expanded operations. However, most surveys are derived from the perspective of UAS own operating mechanism and barely consider interactions of their non-segregated activities with the Air Traffic Management(ATM) system. Hence, to fill the gap, this paper presents a survey conducted from the perspective of Air Navigation Service Provider(ANSP), which serves to accommodate these new entrants to the overall national airspace while continuing flight safety and efficiency. The primary objectives of this paper are to:(A) describe what typical ANSP-supplied UAS Traffic Management(UTM) architecture is required to facilitate all types of civil UAS operations;(B) identify three major ANSP considerations on how UAS can be accommodated safely in civil airspace;(C) outline future directions and challenges related with UAS operations for the ANSP.展开更多
In this paper,we investigate the peaking issue of extended state observers and the anti-disturbance control problem of tethered aircraft systems subject to the unstable flight of the main aircraft,airflow disturbances...In this paper,we investigate the peaking issue of extended state observers and the anti-disturbance control problem of tethered aircraft systems subject to the unstable flight of the main aircraft,airflow disturbances and deferred output constraints.Independent of exact initial values,a modified extended state observer is constructed from a shifting function such that not only the peaking issue inherently in the observer is circumvented completely but also the accurate estimation of the lumped disturbance is guaranteed.Meanwhile,to deal with deferred output constraints,an improved output constrained controller is employed by integrating the shifting function into the barrier Lyapunov function.Then,by combining the modified observer and the improved controller,an anti-disturbance control scheme is presented,which ensures that the outputs with any bounded initial conditions satisfy the constraints after a pre-specified finite time,and the tethered aircraft tracks the desired trajectory accurately.Finally,both a theoretical proof and simulation results verify the effectiveness of the proposed control scheme.展开更多
An Unmanned Aircraft System （UAS） is an aircraft or ground station that can be either remote controlled manually or is capable of flying autonomously under the guidance of pre-programmed Global Positioning System （...An Unmanned Aircraft System （UAS） is an aircraft or ground station that can be either remote controlled manually or is capable of flying autonomously under the guidance of pre-programmed Global Positioning System （GPS） waypoint flight plans or more complex onboard intelligent systems. The UAS aircrafts have recently found extensive applications in military reconnaissance and surveillance, homeland security, precision agriculture, fire monitoring and analysis, and other different kinds of aids needed in disasters. Through surveillance videos captured by a UAS digital imaging payload over the interest areas, the corresponding UAS missions can be conducted. In this paper, the authors present an effective method to detect and extract architectural buildings under rural environment from UAS video sequences. The SIFT points are chosen as image features. The planar homography is adopted as the motion model between different image frames. The proposed algorithm is tested on real UAS video data.展开更多
An aircraft tractor plays a significant role as a kind of important marine transport and support equipment. It＇s necessary to study its controlling and manoeuvring stability to improve operation efficiency. A virtual...An aircraft tractor plays a significant role as a kind of important marine transport and support equipment. It＇s necessary to study its controlling and manoeuvring stability to improve operation efficiency. A virtual prototyping model of the tractor-aircraft system based on Lagrange＇s equation of the first kind with Lagrange mutipliers was established in this paper, According to the towing characteristics, a path-tracking controller using fuzzy logic theory was designed. Direction control herein was carried out through a compensatory tracking approach. Interactive co-simulation was performed to validate the path-tracking behavior in closed-loop, Simulation results indicated that the tractor followed the reference courses precisely on a flat ground.展开更多
The technology of electric propulsion aircraft(EPA)represents an important direction and an advanced stage in the development of aviation electrification.It is a key pathway for green development in aviation industry ...The technology of electric propulsion aircraft(EPA)represents an important direction and an advanced stage in the development of aviation electrification.It is a key pathway for green development in aviation industry and can significantly enhance the energy efficiency of aircraft propulsion system.Electric motor is the most critical electromechanical energy conversion component in an aircraft electric propulsion system(EPS).High-performance electric motors,power electronic converters and EPS control form the foundation of the EPA.This paper provides an overview of the characteristics of electric motors for EPA,analyzes the inverter topologies of EPSs,and reviews ongoing EPA projects.The article highlights the latest advancements in three types of motors:superconducting motors(SCMs),permanent magnet synchronous motors(PMSMs),and induction motors(IMs).It summarizes the control system architectures of current EPA initiatives and,building on this foundation,proposes future research directions for EPSs.These include cutting-edge areas such as high-performance motors and advanced manufacturing technologies,Ga N-or Si C-based inverter integration and innovation,electric propulsion control systems,and optimization of wiring systems.展开更多
In view of the deficiencies in aspects such as failure rate requirements and analysis assumptions of advisory circular,this paper investigates the sources of high safety requirements,and the top-down design method for...In view of the deficiencies in aspects such as failure rate requirements and analysis assumptions of advisory circular,this paper investigates the sources of high safety requirements,and the top-down design method for the flight control system life cycle.Correspondingly,measures are proposed,including enhancing the safety target value to 10^(−10)per flight hour and implementing development assurance.In view of the shortcomings of mainstream aircraft flight control systems,such as weak backup capability and complex fault reconfiguration logic,improvements have been made to the system’s operating modes,control channel allocation,and common mode failure mitigation schemes based on the existing flight control architecture.The flight control design trends and philosophies have been analyzed.A flight control system architecture scheme is proposed,which includes three operating modes and multi-level voters/monitors,three main control channels,and a backup system independent of the main control system,which has been confirmed through functional modeling simulations.The proposed method plays an important role in the architecture design of safety-critical flight control system.展开更多
The variation of the nonlinear contact stiffness induced by the elastic wheel-holding effect between the aircraft and tractor has an important effect on the vibration characteristics of an airfield towbarless traction...The variation of the nonlinear contact stiffness induced by the elastic wheel-holding effect between the aircraft and tractor has an important effect on the vibration characteristics of an airfield towbarless traction system,making it essential for ensuring the safety of this emerging towing-out mode.In this paper,the frequency evolutionary tendency of the traction system is studied and obtained considering the variation of nonlinear contact stiffness for the first time.A novel modal analysis method,based on a derived nonlinear contact relationship,is proposed to investigate the vibration characteristics for mechanical system.Frequency veering and mode exchange phenomena in the low-order modes are observed due to the variation of nonlinear contact stiffness.These findings are further validated by the experimental results of a scaled-down model.In addition,it is also found that the veering critical point will be shifted with the external loads.The study provides valuable insights into the vibration characteristics and frequency veering behavior of similar mechanism-based systems,such as towbarless traction system,and has important implications for improving their design and operational performance.展开更多
To obtain the certificate of airworthiness,it is essential to conduct a full-scale aircraft static test.During such test,accurate and comprehensive wing deformation measurement is crucial for assessing its strength,st...To obtain the certificate of airworthiness,it is essential to conduct a full-scale aircraft static test.During such test,accurate and comprehensive wing deformation measurement is crucial for assessing its strength,stiffness,and bearing capability.This paper proposes a novel and cost-effective videogrammetric method using multi-camera system to achieve the non-contact,highprecision,and 3D measurement of overall static deformation for the large-scale wing structure.To overcome the difficulties of making,carrying,and employing the large 2D or 3D target for calibrating the cameras with large field of view,a flexible stereo cameras calibration method combining 1D target and epipolar geometry is proposed.The global calibration method,aided by a total station,is employed to unify the 3D data obtained from various binocular subsystems.A series of static load tests using a 10-meter-long large-scale wing have been conducted to validate the proposed system and methods.Furthermore,the proposed method was applied to the practical wing deformation measurement of both wings with a wingspan of 33.6 m in the full-size civil aircraft static test.The overall 3D profile and displacement data of the tested wing under various loads can be accurately obtained.The maximum error of distance and displacement measurement is less than 4.5 mm within the measurement range of 35 m in all load cases.These results demonstrate that the proposed method achieves effective,high-accuracy,on-site,and visualized wing deformation measurement,making it a promising approach for full-scale aircraft wing static test.展开更多
This paper presents a thermophysical study approach for a pure environmental control system(ECS),incorporating the geometric dimensions of heat exchangers,ram air duct,and air cycle machine(ACM)blades of the Sabreline...This paper presents a thermophysical study approach for a pure environmental control system(ECS),incorporating the geometric dimensions of heat exchangers,ram air duct,and air cycle machine(ACM)blades of the Sabreliner’s environmental control system.Real flight scenarios are simulated by considering flight input variables such as altitude,aircraft speed,compression ratio of the air cycle machine,and the mass flow rate of bleed air.The study evaluates the coefficient of performance(COP)of the environmental control system,the heat exchanger efficiencies,and the work distribution of the air cycle machine based on five flight scenarios,with a particular focus on considering the effects of humidity on environmental control system performance.The results demonstrate that at cruising altitude(11,000 m),air humidity conditions allow an increase in the COP of around 9.28%compared to dry conditions.Conversely,on land,humidity conditions reduce the performance by 4.26%compared to dry conditions.It was also found that the effects of humidity at high aircraft speeds become negligible.In general terms,the humidity conditions in the air proved to have positive effects on the environmental control system’s performance but negative effects on the heat exchanger efficiencies,reducing them by 0.22%.Additionally,land conditions reflect significant improvements in performance when the compression ratio of the air cycle machine is varied.Furthermore,in the work distribution of the air cycle machine,humidity conditions were demonstrated to consume 2.91%less work fromthe turbine compared to dry conditions.展开更多
The aircraft braking system is critical to ensure the safe take-off and landing of the aircraft.However,the braking system is often exposed to high temperatures and strong vibration working environments,which makes th...The aircraft braking system is critical to ensure the safe take-off and landing of the aircraft.However,the braking system is often exposed to high temperatures and strong vibration working environments,which makes the sensor prone to failure.Sensor failure has the potential to compromise aircraft safety.In order to improve the safety of the aircraft braking system,a fault detection and fault-tolerant control(FDFTC)strategy for the aircraft brake pressure sensor is designed.Firstly,a model based on a bidirectional long short-term memory(Bi-LSTM)network is constructed to estimate the brake pressure.Then,the residual sequence is obtained by comparing the measured pressure with the estimated pressure.On this basis,the improved sequential probability ratio test(SPRT)method based on mathematical statistics is applied to analyze the residual sequence to detect the fault.Finally,simulation and hardware-in-the-loop(HIL)testing results indicate that the proposed FDFTC strategy can detect sensor faults in time and efficiently complete braking when faults occur.Hence,the proposed FDFTC strategy can effectively deal with the faults of the aircraft brake pressure sensor,which is of great significance to improve the reliability and safety of the aircraft.展开更多
Aircraft assembly is characterized by stringent precedence constraints,limited resource availability,spatial restrictions,and a high degree of manual intervention.These factors lead to considerable variability in oper...Aircraft assembly is characterized by stringent precedence constraints,limited resource availability,spatial restrictions,and a high degree of manual intervention.These factors lead to considerable variability in operator workloads and significantly increase the complexity of scheduling.To address this challenge,this study investigates the Aircraft Pulsating Assembly Line Scheduling Problem(APALSP)under skilled operator allocation,with the objective of minimizing assembly completion time.A mathematical model considering skilled operator allocation is developed,and a Q-Learning improved Particle Swarm Optimization algorithm(QLPSO)is proposed.In the algorithm design,a reverse scheduling strategy is adopted to effectively manage large-scale precedence constraints.Moreover,a reverse sequence encoding method is introduced to generate operation sequences,while a time decoding mechanism is employed to determine completion times.The problem is further reformulated as a Markov Decision Process(MDP)with explicitly defined state and action spaces.Within QLPSO,the Q-learning mechanism adaptively adjusts inertia weights and learning factors,thereby achieving a balance between exploration capability and convergence performance.To validate the effectiveness of the proposed approach,extensive computational experiments are conducted on benchmark instances of different scales,including small,medium,large,and ultra-large cases.The results demonstrate that QLPSO consistently delivers stable and high-quality solutions across all scenarios.In ultra-large-scale instances,it improves the best solution by 25.2%compared with the Genetic Algorithm(GA)and enhances the average solution by 16.9%over the Q-learning algorithm,showing clear advantages over the comparative methods.These findings not only confirm the effectiveness of the proposed algorithm but also provide valuable theoretical references and practical guidance for the intelligent scheduling optimization of aircraft pulsating assembly lines.展开更多
A tilt rotor is an aircraft of a special kind, which possesses the characteristics of a helicopter and a fixed-wing airplane. However, there are a great number of important technical problems waiting for settlements. ...A tilt rotor is an aircraft of a special kind, which possesses the characteristics of a helicopter and a fixed-wing airplane. However, there are a great number of important technical problems waiting for settlements. Of them, the flight control system might be a critical one. This article presents the progresses of the research work on the design of flight control system at Nanjing University of Aeronautics and Astronautics (NUAA). The flight control law of the tilt rotor aircraft is designed with the help ...展开更多
As a matured technique used in many fields,the distributed computer system is still a new management method for the aeronautical electrical power distribution system in our country. In this paper, a novel aircraft ele...As a matured technique used in many fields,the distributed computer system is still a new management method for the aeronautical electrical power distribution system in our country. In this paper, a novel aircraft electrical power distribution system based on the distributed computer system is proposed. The principles, features and structure of the aircraft electrical power distribution system and the distributed computer system named electrical load management system (ELMS) are studied. The ELMS composed of four electrical load management centers (ELMCs) and two power source processors (PSPs) operates in the 1553B buses. Principles of the ELMCs and the PSPs are introduced. With the application of the distributed computer system, the aircraft electrical power distribution system is simple, adaptable and flexible.展开更多
The computer numerical control（CNC） system is suited to control varied types of flexible fixtures in aircraft component manufacturing and assembly. The mechanisms and control requirements of flexible fixtures are pr...The computer numerical control（CNC） system is suited to control varied types of flexible fixtures in aircraft component manufacturing and assembly. The mechanisms and control requirements of flexible fixtures are presented and analyzed. The hardware and software architecture and implementation of CNC system are pro- posed. The flexible fixture mechanism is described using configuration parameters. According to the parameters, the CNC system automatically generates the control feature and the human machine interface （HMI） operation function. The CNC system is implemented in a flexible fixture for skin-strlnger assembly, and results show the effectiveness of the system.展开更多
An optimal design method for an aircraft low-power thermoelectric refrigeration system（TRS）is proposed using an existing experimental model as the research platform under given aircraft flight conditions.The variati...An optimal design method for an aircraft low-power thermoelectric refrigeration system（TRS）is proposed using an existing experimental model as the research platform under given aircraft flight conditions.The variation curves of the cooling capacities and the refrigeration coefficients of the system running at three flight altitudes are investigated.The performance of the system is evaluated by the minimum-entropy-generation method and the performance penalty is also calculated.The power variation curves of the cooling system are obtained by an electric power experiment.The peak values of these curves are less than the maximal electric power supply of airborne equipment,proving that the use of the low-power TRS for airborne equipment is feasible.The COP,cooling capacity and entropy generation of the system are relative to the flight altitude and the current of the TRS.Through the analyses of these data,the optimal values of the COP are obtained,and the optimization measures are proposed to maximize the use of the advantages of the TRS.展开更多
The use of unmanned aircraft systems(UAS)for critical public service missions by public organizations,local governments,and social users is expanding.Robust radio transmission by unmanned aerial vehicles(UAVs)is indis...The use of unmanned aircraft systems(UAS)for critical public service missions by public organizations,local governments,and social users is expanding.Robust radio transmission by unmanned aerial vehicles(UAVs)is indispensable in these applications.One of the standards suitable for UAV wireless communications is local 5G.However,to introduce local 5G into a UAS,several problems specific to UASes must be solved.Challenges include the deterioration of the signal-to-noise ratio due to topography and obstacles,the uncertainty of the communication environment due to the movement of multiple UAVs,and the limitation of the frequency bandwidth.To address these problems and to introduce local 5G into the UAS,we propose a novel communication scheduling method.The method incorporates transmission modes with diversity.Our evaluations shows that total data volumes increase by 1.9~3 times with the proposed scheduling method compared with transmission without diversity or efficient scheduling.展开更多
The evaluation system of aircraft noise and environment noise should be integrated, because aircraft noise belongs to environment noise. At the same time, there should be some difference in the evaluation system of ai...The evaluation system of aircraft noise and environment noise should be integrated, because aircraft noise belongs to environment noise. At the same time, there should be some difference in the evaluation system of aircraft noise. For solving this contradiction, this article puts forward a new evaluation system of aircraft noise. This new system unifies the evaluation of aircraft noise and other environment noise effectively, and adds a new evaluation index single event noise exposure level. The system not only considers the characteristics of aircraft noise, which is different from other traffic noise, but also adds aircraft noise to other traffic noise, which can reflect sound environment around airport really. This system has practical worthiness and theory significance.展开更多
Unmanned agricultural aircraft system(UAAS)hasbeen widely employed as a low-cost and reliable method to apply agrochemicals to small agricultural fields in China.The performance of battery-poweredmultirotor UAAS has a...Unmanned agricultural aircraft system(UAAS)hasbeen widely employed as a low-cost and reliable method to apply agrochemicals to small agricultural fields in China.The performance of battery-poweredmultirotor UAAS has attracted considerable attention from manufacturers and researchers.The objective of this research was to design a UAAS equippingwith a data acquisition system,to characterize its chemical application performance based on droplet deposition data and optimize the operating parameters.Each test was repeated three times to assess the reliability of the spraying system.Various flight parameters were also evaluated.The optimal spray pressure for the XR8001 and XR8002(TeeJet,Wheaton,IL,USA)nozzles was found to be 300 kPa,and the latter nozzle had a higher droplet deposition rate and spray volume.Spray volume was not significantly affected by the flight speed or droplet density and was negatively correlated with the nozzle pressure.The results of this study provide a basis for improving the efficiency of UAAS chemicalapplication systems in terms of large-scale application.展开更多
Prognostics and Health Management(PHM) has become a very important tool in modern commercial aircraft. Considering limited built-in sensing devices on the legacy aircraft model,one of the challenges for airborne syste...Prognostics and Health Management(PHM) has become a very important tool in modern commercial aircraft. Considering limited built-in sensing devices on the legacy aircraft model,one of the challenges for airborne system health monitoring is to find an appropriate health indicator that is highly related to the actual degradation state of the system. This paper proposed a novel health indicator extraction method based on the available sensor parameters for the health monitoring of Air Conditioning System(ACS) of a legacy commercial aircraft model. Firstly, a specific Airplane Condition Monitoring System(ACMS) report for ACS health monitoring is defined. Then a non-parametric modeling technique is adopted to calculate the health indicator based on the raw ACMS report data. The proposed method is validated on a single-aisle commercial aircraft widely used for short and medium-haul routes, using more than 6000 ACMS reports collected from a fleet of aircraft during one year. The case study result shows that the proposed health indicator can effectively characterize the degradation state of the ACS, which can provide valuable information for proactive maintenance plan in advance.展开更多
基金Aeronautical Science Foundation of China (2006ZA51004)Fanzhou Foundation of China(20100506)
文摘During the process of aircraft design, the mathematical model of pilot control behavior characteristics is always used to predict aircraft flying qualities （FQ）. This is one of the important methods to avoid pilot-aircraft adverse coupling. In order to study the FQ criterion based on closed-loop pilot-aircraft systems, first, an experimental database is built, which includes 40 aircraft dynamics configurations and the corresponding flight simulation results. Second, the mathematical pilot models with a set of different aircraft configurations are obtained by this experimental database. Then, two FQ criteria, Neal-Smith criterion and Moscow Aviation Institute （MAI） criterion, are analyzed. And the relationship between the FQ level evaluated by actual pilot and the parameters of closed-loop pilot-aircraft systems is studied. Finally, an improved criterion of aircraft FQ is built based on the above two criteria. This new criterion is further used to predict FQ for four new aircraft dynamics configurations, and the prediction results verify its accuracy and practicability.
基金co-supported by the Outstanding Youth Fund of the National Natural Science Foundation of China (No. 61822102)the MIIT Technological Base Program (No. JSZL2016601B003)the National Key Research and Development Program (No. 2018YFB0505105)。
文摘Unmanned Aircraft Systems(UASs) have advanced technologically and surged exponentially over recent years. Currently, due to safety concerns, most civil operations of UAS are conducted in low-level uncontrolled area or in segregated controlled airspace. As the industry progresses, both operational and technological capabilities have matured to the point where UASs are expected to gain greater freedom of access to both controlled and uncontrolled airspace. Extensive technical and regulatory surveys have been conducted to enable the expanded operations. However, most surveys are derived from the perspective of UAS own operating mechanism and barely consider interactions of their non-segregated activities with the Air Traffic Management(ATM) system. Hence, to fill the gap, this paper presents a survey conducted from the perspective of Air Navigation Service Provider(ANSP), which serves to accommodate these new entrants to the overall national airspace while continuing flight safety and efficiency. The primary objectives of this paper are to:(A) describe what typical ANSP-supplied UAS Traffic Management(UTM) architecture is required to facilitate all types of civil UAS operations;(B) identify three major ANSP considerations on how UAS can be accommodated safely in civil airspace;(C) outline future directions and challenges related with UAS operations for the ANSP.
基金supported by the National Natural Science Foundation of China(61725303,91848205)。
文摘In this paper,we investigate the peaking issue of extended state observers and the anti-disturbance control problem of tethered aircraft systems subject to the unstable flight of the main aircraft,airflow disturbances and deferred output constraints.Independent of exact initial values,a modified extended state observer is constructed from a shifting function such that not only the peaking issue inherently in the observer is circumvented completely but also the accurate estimation of the lumped disturbance is guaranteed.Meanwhile,to deal with deferred output constraints,an improved output constrained controller is employed by integrating the shifting function into the barrier Lyapunov function.Then,by combining the modified observer and the improved controller,an anti-disturbance control scheme is presented,which ensures that the outputs with any bounded initial conditions satisfy the constraints after a pre-specified finite time,and the tethered aircraft tracks the desired trajectory accurately.Finally,both a theoretical proof and simulation results verify the effectiveness of the proposed control scheme.
文摘An Unmanned Aircraft System （UAS） is an aircraft or ground station that can be either remote controlled manually or is capable of flying autonomously under the guidance of pre-programmed Global Positioning System （GPS） waypoint flight plans or more complex onboard intelligent systems. The UAS aircrafts have recently found extensive applications in military reconnaissance and surveillance, homeland security, precision agriculture, fire monitoring and analysis, and other different kinds of aids needed in disasters. Through surveillance videos captured by a UAS digital imaging payload over the interest areas, the corresponding UAS missions can be conducted. In this paper, the authors present an effective method to detect and extract architectural buildings under rural environment from UAS video sequences. The SIFT points are chosen as image features. The planar homography is adopted as the motion model between different image frames. The proposed algorithm is tested on real UAS video data.
基金Harbin Technological Innovation Research Fund(NO:2012RFXXG039)
文摘An aircraft tractor plays a significant role as a kind of important marine transport and support equipment. It＇s necessary to study its controlling and manoeuvring stability to improve operation efficiency. A virtual prototyping model of the tractor-aircraft system based on Lagrange＇s equation of the first kind with Lagrange mutipliers was established in this paper, According to the towing characteristics, a path-tracking controller using fuzzy logic theory was designed. Direction control herein was carried out through a compensatory tracking approach. Interactive co-simulation was performed to validate the path-tracking behavior in closed-loop, Simulation results indicated that the tractor followed the reference courses precisely on a flat ground.
基金supported by the National Nature Science Foundation of China(Grant No.52302507)。
文摘The technology of electric propulsion aircraft(EPA)represents an important direction and an advanced stage in the development of aviation electrification.It is a key pathway for green development in aviation industry and can significantly enhance the energy efficiency of aircraft propulsion system.Electric motor is the most critical electromechanical energy conversion component in an aircraft electric propulsion system(EPS).High-performance electric motors,power electronic converters and EPS control form the foundation of the EPA.This paper provides an overview of the characteristics of electric motors for EPA,analyzes the inverter topologies of EPSs,and reviews ongoing EPA projects.The article highlights the latest advancements in three types of motors:superconducting motors(SCMs),permanent magnet synchronous motors(PMSMs),and induction motors(IMs).It summarizes the control system architectures of current EPA initiatives and,building on this foundation,proposes future research directions for EPSs.These include cutting-edge areas such as high-performance motors and advanced manufacturing technologies,Ga N-or Si C-based inverter integration and innovation,electric propulsion control systems,and optimization of wiring systems.
文摘In view of the deficiencies in aspects such as failure rate requirements and analysis assumptions of advisory circular,this paper investigates the sources of high safety requirements,and the top-down design method for the flight control system life cycle.Correspondingly,measures are proposed,including enhancing the safety target value to 10^(−10)per flight hour and implementing development assurance.In view of the shortcomings of mainstream aircraft flight control systems,such as weak backup capability and complex fault reconfiguration logic,improvements have been made to the system’s operating modes,control channel allocation,and common mode failure mitigation schemes based on the existing flight control architecture.The flight control design trends and philosophies have been analyzed.A flight control system architecture scheme is proposed,which includes three operating modes and multi-level voters/monitors,three main control channels,and a backup system independent of the main control system,which has been confirmed through functional modeling simulations.The proposed method plays an important role in the architecture design of safety-critical flight control system.
基金co-supported by the Key Projects of the Civil Aviation Joint Fund of the National Natural Science Foundation of China(No.U2033208)。
文摘The variation of the nonlinear contact stiffness induced by the elastic wheel-holding effect between the aircraft and tractor has an important effect on the vibration characteristics of an airfield towbarless traction system,making it essential for ensuring the safety of this emerging towing-out mode.In this paper,the frequency evolutionary tendency of the traction system is studied and obtained considering the variation of nonlinear contact stiffness for the first time.A novel modal analysis method,based on a derived nonlinear contact relationship,is proposed to investigate the vibration characteristics for mechanical system.Frequency veering and mode exchange phenomena in the low-order modes are observed due to the variation of nonlinear contact stiffness.These findings are further validated by the experimental results of a scaled-down model.In addition,it is also found that the veering critical point will be shifted with the external loads.The study provides valuable insights into the vibration characteristics and frequency veering behavior of similar mechanism-based systems,such as towbarless traction system,and has important implications for improving their design and operational performance.
文摘To obtain the certificate of airworthiness,it is essential to conduct a full-scale aircraft static test.During such test,accurate and comprehensive wing deformation measurement is crucial for assessing its strength,stiffness,and bearing capability.This paper proposes a novel and cost-effective videogrammetric method using multi-camera system to achieve the non-contact,highprecision,and 3D measurement of overall static deformation for the large-scale wing structure.To overcome the difficulties of making,carrying,and employing the large 2D or 3D target for calibrating the cameras with large field of view,a flexible stereo cameras calibration method combining 1D target and epipolar geometry is proposed.The global calibration method,aided by a total station,is employed to unify the 3D data obtained from various binocular subsystems.A series of static load tests using a 10-meter-long large-scale wing have been conducted to validate the proposed system and methods.Furthermore,the proposed method was applied to the practical wing deformation measurement of both wings with a wingspan of 33.6 m in the full-size civil aircraft static test.The overall 3D profile and displacement data of the tested wing under various loads can be accurately obtained.The maximum error of distance and displacement measurement is less than 4.5 mm within the measurement range of 35 m in all load cases.These results demonstrate that the proposed method achieves effective,high-accuracy,on-site,and visualized wing deformation measurement,making it a promising approach for full-scale aircraft wing static test.
文摘This paper presents a thermophysical study approach for a pure environmental control system(ECS),incorporating the geometric dimensions of heat exchangers,ram air duct,and air cycle machine(ACM)blades of the Sabreliner’s environmental control system.Real flight scenarios are simulated by considering flight input variables such as altitude,aircraft speed,compression ratio of the air cycle machine,and the mass flow rate of bleed air.The study evaluates the coefficient of performance(COP)of the environmental control system,the heat exchanger efficiencies,and the work distribution of the air cycle machine based on five flight scenarios,with a particular focus on considering the effects of humidity on environmental control system performance.The results demonstrate that at cruising altitude(11,000 m),air humidity conditions allow an increase in the COP of around 9.28%compared to dry conditions.Conversely,on land,humidity conditions reduce the performance by 4.26%compared to dry conditions.It was also found that the effects of humidity at high aircraft speeds become negligible.In general terms,the humidity conditions in the air proved to have positive effects on the environmental control system’s performance but negative effects on the heat exchanger efficiencies,reducing them by 0.22%.Additionally,land conditions reflect significant improvements in performance when the compression ratio of the air cycle machine is varied.Furthermore,in the work distribution of the air cycle machine,humidity conditions were demonstrated to consume 2.91%less work fromthe turbine compared to dry conditions.
基金Supported by National Natural Science Foundation of China(Grant No.52205045)National Key Research and Development Program of China(Grant No.2021YFB2011300)+2 种基金Aeronautical Science Foundation of China(Grant No.2022Z029051001)Zhejiang Provincial Natural Science Foundation of China(Grant No.LZ24E050006)Research Fund of State Key Laboratory of Mechanics and Control for Aerospace Structures(Nanjing University of Aeronautics and Astronautics)(Grant No.MCAS-E-0224G01).
文摘The aircraft braking system is critical to ensure the safe take-off and landing of the aircraft.However,the braking system is often exposed to high temperatures and strong vibration working environments,which makes the sensor prone to failure.Sensor failure has the potential to compromise aircraft safety.In order to improve the safety of the aircraft braking system,a fault detection and fault-tolerant control(FDFTC)strategy for the aircraft brake pressure sensor is designed.Firstly,a model based on a bidirectional long short-term memory(Bi-LSTM)network is constructed to estimate the brake pressure.Then,the residual sequence is obtained by comparing the measured pressure with the estimated pressure.On this basis,the improved sequential probability ratio test(SPRT)method based on mathematical statistics is applied to analyze the residual sequence to detect the fault.Finally,simulation and hardware-in-the-loop(HIL)testing results indicate that the proposed FDFTC strategy can detect sensor faults in time and efficiently complete braking when faults occur.Hence,the proposed FDFTC strategy can effectively deal with the faults of the aircraft brake pressure sensor,which is of great significance to improve the reliability and safety of the aircraft.
基金supported by the National Natural Science Foundation of China(Grant No.52475543)Natural Science Foundation of Henan(Grant No.252300421101)+1 种基金Henan Province University Science and Technology Innovation Talent Support Plan(Grant No.24HASTIT048)Science and Technology Innovation Team Project of Zhengzhou University of Light Industry(Grant No.23XNKJTD0101).
文摘Aircraft assembly is characterized by stringent precedence constraints,limited resource availability,spatial restrictions,and a high degree of manual intervention.These factors lead to considerable variability in operator workloads and significantly increase the complexity of scheduling.To address this challenge,this study investigates the Aircraft Pulsating Assembly Line Scheduling Problem(APALSP)under skilled operator allocation,with the objective of minimizing assembly completion time.A mathematical model considering skilled operator allocation is developed,and a Q-Learning improved Particle Swarm Optimization algorithm(QLPSO)is proposed.In the algorithm design,a reverse scheduling strategy is adopted to effectively manage large-scale precedence constraints.Moreover,a reverse sequence encoding method is introduced to generate operation sequences,while a time decoding mechanism is employed to determine completion times.The problem is further reformulated as a Markov Decision Process(MDP)with explicitly defined state and action spaces.Within QLPSO,the Q-learning mechanism adaptively adjusts inertia weights and learning factors,thereby achieving a balance between exploration capability and convergence performance.To validate the effectiveness of the proposed approach,extensive computational experiments are conducted on benchmark instances of different scales,including small,medium,large,and ultra-large cases.The results demonstrate that QLPSO consistently delivers stable and high-quality solutions across all scenarios.In ultra-large-scale instances,it improves the best solution by 25.2%compared with the Genetic Algorithm(GA)and enhances the average solution by 16.9%over the Q-learning algorithm,showing clear advantages over the comparative methods.These findings not only confirm the effectiveness of the proposed algorithm but also provide valuable theoretical references and practical guidance for the intelligent scheduling optimization of aircraft pulsating assembly lines.
基金National Natural Science Foundation of China (60705034)
文摘A tilt rotor is an aircraft of a special kind, which possesses the characteristics of a helicopter and a fixed-wing airplane. However, there are a great number of important technical problems waiting for settlements. Of them, the flight control system might be a critical one. This article presents the progresses of the research work on the design of flight control system at Nanjing University of Aeronautics and Astronautics (NUAA). The flight control law of the tilt rotor aircraft is designed with the help ...
文摘As a matured technique used in many fields,the distributed computer system is still a new management method for the aeronautical electrical power distribution system in our country. In this paper, a novel aircraft electrical power distribution system based on the distributed computer system is proposed. The principles, features and structure of the aircraft electrical power distribution system and the distributed computer system named electrical load management system (ELMS) are studied. The ELMS composed of four electrical load management centers (ELMCs) and two power source processors (PSPs) operates in the 1553B buses. Principles of the ELMCs and the PSPs are introduced. With the application of the distributed computer system, the aircraft electrical power distribution system is simple, adaptable and flexible.
文摘The computer numerical control（CNC） system is suited to control varied types of flexible fixtures in aircraft component manufacturing and assembly. The mechanisms and control requirements of flexible fixtures are presented and analyzed. The hardware and software architecture and implementation of CNC system are pro- posed. The flexible fixture mechanism is described using configuration parameters. According to the parameters, the CNC system automatically generates the control feature and the human machine interface （HMI） operation function. The CNC system is implemented in a flexible fixture for skin-strlnger assembly, and results show the effectiveness of the system.
文摘An optimal design method for an aircraft low-power thermoelectric refrigeration system（TRS）is proposed using an existing experimental model as the research platform under given aircraft flight conditions.The variation curves of the cooling capacities and the refrigeration coefficients of the system running at three flight altitudes are investigated.The performance of the system is evaluated by the minimum-entropy-generation method and the performance penalty is also calculated.The power variation curves of the cooling system are obtained by an electric power experiment.The peak values of these curves are less than the maximal electric power supply of airborne equipment,proving that the use of the low-power TRS for airborne equipment is feasible.The COP,cooling capacity and entropy generation of the system are relative to the flight altitude and the current of the TRS.Through the analyses of these data,the optimal values of the COP are obtained,and the optimization measures are proposed to maximize the use of the advantages of the TRS.
基金Part of this work was conducted under a national project,Research and Development of Communication Network Technology for Ef☀-cient Use of Frequency in Unmanned Aircraft Systems,which was supported by the Ministry of Internal Affairs and Communications(MIC),Japan,and this project was supported by the KDDI Foundation,Japan.The associate editor coordinating the review of this paper and approving it for publication was L.Bai.
文摘The use of unmanned aircraft systems(UAS)for critical public service missions by public organizations,local governments,and social users is expanding.Robust radio transmission by unmanned aerial vehicles(UAVs)is indispensable in these applications.One of the standards suitable for UAV wireless communications is local 5G.However,to introduce local 5G into a UAS,several problems specific to UASes must be solved.Challenges include the deterioration of the signal-to-noise ratio due to topography and obstacles,the uncertainty of the communication environment due to the movement of multiple UAVs,and the limitation of the frequency bandwidth.To address these problems and to introduce local 5G into the UAS,we propose a novel communication scheduling method.The method incorporates transmission modes with diversity.Our evaluations shows that total data volumes increase by 1.9~3 times with the proposed scheduling method compared with transmission without diversity or efficient scheduling.
文摘The evaluation system of aircraft noise and environment noise should be integrated, because aircraft noise belongs to environment noise. At the same time, there should be some difference in the evaluation system of aircraft noise. For solving this contradiction, this article puts forward a new evaluation system of aircraft noise. This new system unifies the evaluation of aircraft noise and other environment noise effectively, and adds a new evaluation index single event noise exposure level. The system not only considers the characteristics of aircraft noise, which is different from other traffic noise, but also adds aircraft noise to other traffic noise, which can reflect sound environment around airport really. This system has practical worthiness and theory significance.
基金This work was partially financially supported by the National Key Research and Development Program of China(Grant No.2016YFD0200701).
文摘Unmanned agricultural aircraft system(UAAS)hasbeen widely employed as a low-cost and reliable method to apply agrochemicals to small agricultural fields in China.The performance of battery-poweredmultirotor UAAS has attracted considerable attention from manufacturers and researchers.The objective of this research was to design a UAAS equippingwith a data acquisition system,to characterize its chemical application performance based on droplet deposition data and optimize the operating parameters.Each test was repeated three times to assess the reliability of the spraying system.Various flight parameters were also evaluated.The optimal spray pressure for the XR8001 and XR8002(TeeJet,Wheaton,IL,USA)nozzles was found to be 300 kPa,and the latter nozzle had a higher droplet deposition rate and spray volume.Spray volume was not significantly affected by the flight speed or droplet density and was negatively correlated with the nozzle pressure.The results of this study provide a basis for improving the efficiency of UAAS chemicalapplication systems in terms of large-scale application.
基金supported by the National Natural Science Foundation of China (61403198)the Jiangsu Province Natural Science Foundation of China (BK20140827)China Postdoctoral Science Foundation (2015M581792)
文摘Prognostics and Health Management(PHM) has become a very important tool in modern commercial aircraft. Considering limited built-in sensing devices on the legacy aircraft model,one of the challenges for airborne system health monitoring is to find an appropriate health indicator that is highly related to the actual degradation state of the system. This paper proposed a novel health indicator extraction method based on the available sensor parameters for the health monitoring of Air Conditioning System(ACS) of a legacy commercial aircraft model. Firstly, a specific Airplane Condition Monitoring System(ACMS) report for ACS health monitoring is defined. Then a non-parametric modeling technique is adopted to calculate the health indicator based on the raw ACMS report data. The proposed method is validated on a single-aisle commercial aircraft widely used for short and medium-haul routes, using more than 6000 ACMS reports collected from a fleet of aircraft during one year. The case study result shows that the proposed health indicator can effectively characterize the degradation state of the ACS, which can provide valuable information for proactive maintenance plan in advance.
