In this paper,a practical method named linear active disturbance rejection control(LADRC)with adaptive tuning is proposed for attitude control of small-scale unmanned helicopter.The proposed method accounts for both e...In this paper,a practical method named linear active disturbance rejection control(LADRC)with adaptive tuning is proposed for attitude control of small-scale unmanned helicopter.The proposed method accounts for both external disturbances and internal dynamic uncertainties,as well as parameter deviations arising from parameter uncertainty,while maintaining a relatively small number of adjustable parameters.Furthermore,it addresses the limitation that conventional active disturbance rejection control methods cannot be rigorously analyzed for stability.The total disturbance of unmanned helicopter is estimated and compensated by designed LADRC.The introduction of adaptive control realizes online parameter tuning,which eliminates parameter deviation and further improves control precision.Moreover,it also provides a novel idea to prove the stability of controller,so that it can be analyzed by Lyapunov function.Finally,the anti-disturbance performance and effectiveness of proposed method are verified by numerical simulation.展开更多
This study is dedicated to numerically investigate the dynamic behavior of a missile released from a helicopter under the influence of downwash from the rotating rotors using AGM-114 Hellfire and UH-60 as the testcase...This study is dedicated to numerically investigate the dynamic behavior of a missile released from a helicopter under the influence of downwash from the rotating rotors using AGM-114 Hellfire and UH-60 as the testcase.Simulations are conducted using unsteady Reynolds-averaged Navier-Stokes(URANS)with shear stress transport(SST)k-ωturbulence model,incorporating six-degree-of-freedom(6-DOF)motion and overset grid.Two releasing scenarios,viz.,hover and forward flight,are analyzed under varying missile launch thrust and helicopter forward flight speed.Results reveal that the rotor downwash significantly affects the stability of the missile,particularly during hovering case,where low thrust prolongs wake interaction.In forward flight,the increased airspeed can in principle reduce wake influence but introduces asymmetrical aerodynamic effects on the trajectory of the missile.The findings offer guidance for missile release and launch planning in rotorcraft operations.展开更多
This study presents the development of computationally efficient coupling of Navier–Stokes Computational Fluid Dynamics(CFD)with a helicopter flight dynamics model with the ultimate goal of real-time simulation of ai...This study presents the development of computationally efficient coupling of Navier–Stokes Computational Fluid Dynamics(CFD)with a helicopter flight dynamics model with the ultimate goal of real-time simulation of airwake effects in the helicopter/ship Dynamic Interface(DI).The flight dynamics model is free to move within a computational domain,where the main rotor forces are converted to source terms in the momentum equations of the CFD solution using an actuator disk model.Simultaneously,the CFD solver calculates induced velocities that are fed back to the simulation and affect the aerodynamic loads in the flight dynamics.The CFD solver models the inflow,ground effect and interactional aerodynamics in the flight dynamics simulation,and these calculations can be coupled with the solution of the external flow(e.g.,ship airwake effects).The simulation framework for fully-coupled pilot-in-the-loop(PIL)flight dynamics/CFD is demonstrated for a simplified shedding wake.Initial tests were performed with 0.38 million structured grid cells running on 352 processors and showed near-real-time performance.Improvements to the coupling interface are described that allow the simulation run at near-real-time execution speeds on currently available computing platforms.Improvements in computing hardware are expected to allow real-time simulations.展开更多
A numerical study on flow control of ship airwake during shipboard landing is carried out to address the effect of flow control devices on helicopter rotor airload. The in-house Reynolds Averaged Navier-Stokes(RANS) b...A numerical study on flow control of ship airwake during shipboard landing is carried out to address the effect of flow control devices on helicopter rotor airload. The in-house Reynolds Averaged Navier-Stokes(RANS) based solver Rotorcraft AeroDynamics and Aeroacoustics Solver(RADAS), with combination of momentum source approach is employed to conduct the helicopter shipboard landing simulation. The control effects of three aerodynamic modifications of ship superstructure, i.e. ramp, notch and flap, in different Wind-Over-Deck(WOD) conditions are discussed.From the steady simulation results, the effect of spatial variation of ship airwake on rotor airloads is concluded. The aerodynamic modifications reduce the strength of shedding vortex and increase rotor normal force through delaying and relieving flow separation, and therefore are beneficial to alleviate the limitation of control inputs. By contrast, the perturbation of unsteady ship airwake can cause the serious oscillation of rotor forces during shipboard landing. The unsteady simulations show that the turbulence intensity of ship airwake and oscillatory rotor airloading, represented by Root-Mean-Square(RMS) loading, can be remarkably reduced by the ramp and notch modifications, while the flap modification has adverse effect. It means that flow control devices have large potential benefits to alleviate the pilot's workload and improve the shipboard landing safety, but they should be well designed to avoid the introduction of more vortex, which leads to increase in disturbance of flow field.展开更多
Accurate measurement of helicopter rotor motion parameters(flap,lead-lag,torsion,and azimuth angles)is essential for rotor blade design,helicopter dynamics modeling,and flight safety and health monitoring.However,the ...Accurate measurement of helicopter rotor motion parameters(flap,lead-lag,torsion,and azimuth angles)is essential for rotor blade design,helicopter dynamics modeling,and flight safety and health monitoring.However,the existing methods face challenges in testing equipment installation,calibration,and data transmission,resulting in limited reports on real-time in-flight measurements of blade motion parameters.This paper proposes a non-contact optoelectronic method based on two-dimensional position-sensitive detectors for in-flight measurement and a ground calibration system to obtain real-time rotor motion parameters during helicopter flight.The proposed method establishes the time evolution relationship of rotor motion parameters and verifies the performance of the in-flight measurement system regarding measurement resolution and accuracy through the construction of a blade motion posture experimental platform.The proposed method has been applied to the flight measurement of a medium-sized single-rotor helicopter,and the obtained results have been compared with theoretical analysis outcomes.Furthermore,this paper examines the characteristics of blade motion parameters during flight and discusses the challenges and potential solutions for measuring rotor motion parameters during helicopter flight using the proposed method.展开更多
Airborne landing with shipboard helicopters gradually replaces surface landing to dominate joint amphibious operations.A problem with shipboard helicopter mission planning is conducted in the context of amphibious ope...Airborne landing with shipboard helicopters gradually replaces surface landing to dominate joint amphibious operations.A problem with shipboard helicopter mission planning is conducted in the context of amphibious operations.First,the typical missions of shipborne helicopters in amphibious operations are analyzed.An Amphibious Operational Mission Planning Model for Shipboard Helicopters(AOMPMSH)is established,with the objectives of minimizing the completion time of the amphibious campaign and minimizing troop and helicopter losses,taking the available operational resources and the order of the mission sub-phases into account.Then,a simulationbased amphibious operations effectiveness assessment model is constructed to calculate the optimization objectives of AOMPMSH by simulating the campaign development with an amphibious objective area situation transfer model and simulating the engagement process with a modified Lanchester model.A reference point based multi-objective optimization algorithm is designed to solve the proposed AOMPMSH.The population iteration mechanism employs an initial population generation method and a local search method to solve the problem of vast definition space.The population ranking selection mechanism employs a population distribution based reference point generation method to solve the problem of population irregular distribution.Finally,a simulation case with the background of a battalion-scaled amphibious campaign is presented.The calculation results verify the rationality of the proposed model and the superiority of the designed algorithm and have some reference value for the operational applications of shipboard helicopters in amphibious operations.展开更多
The general structure of ship-borne helicopter landing forecast system is presented, and a novel ship motion prediction model based on minor component analysis (MCA) is built up to improve the forecast effectiveness. ...The general structure of ship-borne helicopter landing forecast system is presented, and a novel ship motion prediction model based on minor component analysis (MCA) is built up to improve the forecast effectiveness. To validate the feasibility of this landing forecast system, time series for the roll, pitch and heave are generated by simulation and then forecasted based on MCA. Simulation results show that ship-borne helicopters can land safely in higher sea condition while carrying on rescue or replenishment tasks at sea in terms of the landing forecast system.展开更多
The ballistic impact identification method for the helicopter Tail Drive Shaft System(TDSS)isn't yet comprehensive,which affects helicopter flight safety.This paper proposes a ballistic impact identification metho...The ballistic impact identification method for the helicopter Tail Drive Shaft System(TDSS)isn't yet comprehensive,which affects helicopter flight safety.This paper proposes a ballistic impact identification method for the TDSS based on vibration response analysis.Based on the Johnson-Cook constitutive model and failure criteria,the ballistic impact finite element simulation model is established,which is verified by the ballistic impact experiment of the Tail Drive Shaft(TDS).Considering the ballistic impact excitation force,the dynamic model of the TDSS with ballistic impact is established,which is verified by finite element commercial software.If a bullet hits the TDS,the bending vibration displacement increases sharply at a certain moment and then significantly increases but remains stable.Meanwhile,the critical speed component appears in the frequency-domain response of bending vibration,and then the speed component significantly increases but remains stable.What's more,the axis trajectory exhibits a sudden,large-scale,and irregular whirling motion at a certain moment,followed by a significant increase but remains stable.Furthermore,if the axial vibration response is small,the bullet core shooting should be considered vertically or at a small incident angle,otherwise,it should be considered at a large incident angle.展开更多
To reduce the vibration of the Coaxial Helicopter Main Transmission System(CHMTS)considering both level and vertical flight conditions,a vibration evaluation and optimization model for the CHMTS was built.The vibratio...To reduce the vibration of the Coaxial Helicopter Main Transmission System(CHMTS)considering both level and vertical flight conditions,a vibration evaluation and optimization model for the CHMTS was built.The vibration simulation model of the CHMTS was set up by gear dynamics theory and loaded contact analysis.For better evaluation of the system vibration,a vibration evaluation method for the CHMTS was established by the G1 method-variation coefficient method.A hybrid Gravitational Search Algorithm-Simulated Annealing(GSA-SA)algorithm was combined to balance convergence speed and searching accuracy.The principle test was conducted to prove the accuracy of theoretical method,in which the maximum relative error is16.26%.The optional results show that the vibration of the optimized transmission system decreases significantly,in which the maximum reduction of key vibration indicators reaches more than 20%.The theoretical results have been compared to the experiment to verify the effectiveness of the vibration optimization method.The proposed method could be extended to other fields.展开更多
This paper presents a comprehensive test and systematic evaluation analysis of cabin noise in the Robinson R44 RAVEN II helicopter.Initially,microphones were placed within the cabin to conduct systematic assessments o...This paper presents a comprehensive test and systematic evaluation analysis of cabin noise in the Robinson R44 RAVEN II helicopter.Initially,microphones were placed within the cabin to conduct systematic assessments of noise levels under various flight conditions,including takeoff,climbing,level flight,landing,hovering,etc.Subsequently,time–frequency analysis was conducted on the test data utilizing traditional A-weighted sound pressure levels,which was followed by quantitative comparisons across different flight conditions.Then,detailed evaluation and discussion were conducted,taking into account the subjective perceptions and communication challenges of cabin crew members.This assessment incorporated the use of aviation noise indicators,speech interference levels,and metrics related to sound quality.Finally,potential noise reduction measures and their effects were preliminarily discussed.The results indicate that helicopter cabin noise exhibited variations across different flight states or positions within the same state,ranging from 87.6 d B(A)to 92.6 dB(A).Discrepancies between A-weighted sound pressure level and psychoacoustic parameters were observed,particularly during hovering states,which indicate that there is a necessity for the combination of multiple evaluation indicators.Notably,damping measure can serve as a pivotal factor in mitigating cabin noise.展开更多
For the research of helicopter/ship dynamic interface,the method of combining steady flow and stochastic flow is adopted to establish a flow field model applied to the flight dynamics analysis of shipborne helicopter....For the research of helicopter/ship dynamic interface,the method of combining steady flow and stochastic flow is adopted to establish a flow field model applied to the flight dynamics analysis of shipborne helicopter.The steady flow is calculated by computational fluid dynamics(CFD)method,while the stochastic flow is composed of the compensation velocity derived from ship motion and turbulence above the deck.The accuracy of the proposed flow field model is verified by comparing the helicopter response in the proposed flow field with the results calculated by US Army′s Military Specifications(MIL)model which is commonly used in engineering.Meanwhile,it also shows the proposed flow field model is more appliable to flight dynamics analysis of shipborne helicopter.On that the basis,ship deck flow field is simulated at different sea conditions by adjusting the wind speed on the deck,mother ship movement and shipboard turbulence,etc.And helicopter angular rate response is calculated.The results show that the difference of dynamic stability between helicopter′s roll and pitch leads to the facts that the influence of above factors on the helicopter′s roll angular rate response is greater than that of pitch angular rate,that the frequency and amplitude of mother ship roll motion are much greater than those of pitch motion,and that the disturbance caused by roll motion on the air has greater influence on the helicopter response.The shipboard turbulence is the main disturbance factor that influences helicopter flight stability and its intensity determines the amplitudes of angular rate response.展开更多
An advanced Actuator Surface Method(ASM)coupled with Computational Fluid Dynamics(CFD)is developed and applied to the complex unsteady aerodynamic simulation of helicopter.By introducing an improved three-dimensional ...An advanced Actuator Surface Method(ASM)coupled with Computational Fluid Dynamics(CFD)is developed and applied to the complex unsteady aerodynamic simulation of helicopter.By introducing an improved three-dimensional anisotropic Gaussian kernel,this method effectively addresses the severe aerodynamic load fluctuations commonly associated with traditional Virtual Blade Method(VBM)due to turbulent flow around blade elements.To manage the issues of regional shape and grid cell quantity variations caused by virtual blade sweeping,a universal hybrid grid generation strategy is established without body-fitted and disk interpolation grids,which enhances the computational stability at both blade elements and blade edges.Aerodynamic numerical simulations of helicopter are performed using this method,focusing on rotor/fuselage interaction dominated by rotor wake motion and fuselage blockage effects,Blade-Vortex Interaction(BVI)induced by tip vortices,and maneuvering flights involving collective pitch ramp increases.The results indicate that the advanced ASM demonstrates reliability and robustness in the simulation of complex unsteady flow fields around helicopter.Under similar computational accuracy,the advanced ASM improves computational efficiency by nearly 40 times compared to the oversetgrid-based full Blade-Resolved(B-R)method,and by 6 times compared to the VBM.It shows significant advantages when applied to complex full-aircraft interaction and maneuvering flight conditions that require substantial computational resources.展开更多
To achieve high-precision trajectory following during helicopter maneuver tasks and reduce the disruptive influences of unknown variabilities,this study introduces a cascaded-loop helicopter trajectory tracking contro...To achieve high-precision trajectory following during helicopter maneuver tasks and reduce the disruptive influences of unknown variabilities,this study introduces a cascaded-loop helicopter trajectory tracking controller,whose parameters are set using an Ant Colony OptimizationSlime Mould Algorithm(ACO-SMA).Initially,a nonlinear flight dynamics model of the helicopter is constructed.Observer gain functions and nonlinear feedback from a vibrational suppression function to improve the tracking performance of the controller,addressing issues in disturbance estimation and compensation of the Active Disturbance Rejection Control(ADRC).Simultaneously,a cascaded loop system,comprising an internal attitude loop and an external position loop,is created,and the ant colony-slime mold hybrid algorithm optimizes the system parameters of the trajectory tracking controller.Finally,helicopter trajectory tracking simulation experiments are conducted,including spiral ascending and“8”shape climbing maneuvers.The findings indicate that the ADRC employed for helicopter trajectory tracking exhibits outstanding performance in rejecting disturbances caused by gusts and accurately tracking trajectories.The trajectory tracking controller,whose parameters are optimized by the ACO-SMA,shows higher tracking precision compared to the conventional PID and ADRC,thereby substantially improving the precision of maneuver tasks.展开更多
Ship operations are crucial to global trade,and their decarbonization is essential to mitigate climate change.This study evaluates the economic viability of existing and emerging decarbonization technologies in mariti...Ship operations are crucial to global trade,and their decarbonization is essential to mitigate climate change.This study evaluates the economic viability of existing and emerging decarbonization technologies in maritime shipping using the levelized cost of energy methodology.It includes a detailed comparative analysis based on essential criteria and sensitivity assessments to highlight the economic impacts of technological advancements.Key factors influencing total costs include fuel costs,carbon pricing,and energy demands for carbon capture.The findings reveal that methanol is more cost-effective than heavy fuel oil(HFO)when priced below 3000 CNY/t,assuming HFO costs 4400 CNY/t.Additionally,methanol with post-combustion carbon capture is less expensive than pre-combustion carbon capture.When carbon prices rise above 480 CNY/t,carbon capture technologies prove more economical than purchasing carbon emission allowances for HFO and liquefied natural gas.Enhanc-ing the use of exhaust gas waste heat is recommended for cost savings.Post-combustion carbon capture also shows greater efficiency,requiring about 1.1 GJ/t less energy than pre-combustion methods,leading to lower overall costs.Future research should focus on market mechanisms to stabilize fuel prices and develop less energy-intensive carbon capture technologies.This study offers critical insights into effective decarbonization strategies for advancing global maritime trade in the present and future.展开更多
At Yangpu Port on the northwestern tip of Hainan Island,towering quay cranes are lined in neat rows, hoisting containers on and off cargo vessels in constant motion.“Today, half of the international ships we pilot ar...At Yangpu Port on the northwestern tip of Hainan Island,towering quay cranes are lined in neat rows, hoisting containers on and off cargo vessels in constant motion.“Today, half of the international ships we pilot are ultra-large vessels over 200meters in length,” said Lin Hongpin,head of the Yangpu branch of Hainan Provincial Ship Pilot Station. Since the launch of the island-wide special customs operations, port throughput has continued to climb, with pilotage services for such large ships rising by nearly 20 percent year on year.展开更多
An experimental study of the flow in a helicopter inlet with front output shaft and partial flow dynamic head is conducted in low speed wind tunnel. The flow characters of the inlet in the range of the yaw angle from ...An experimental study of the flow in a helicopter inlet with front output shaft and partial flow dynamic head is conducted in low speed wind tunnel. The flow characters of the inlet in the range of the yaw angle from 0~135°are presented in this paper. The static pressure distributions along the duct, distortions of the flow field at the outlet section and total pressure recovery coefficients are measured and analyzed. The results show that this type of inlet has high total pressure recovery coefficients at a wide range of yaw angle. The regions of local flow separation and distortion are closely related to the yaw angle. It′s also found that the outlet section has the best characteristics at sideslip, and sharply deteriorated characteristics at the yawed flight with a yaw angle of more than 90°展开更多
The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish th...The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish the complete unsteadily aeroelastic coupling analytical model of the tiltrotor. The stability of the tiltrotor in the helicopter mode is analyzed aiming at a semi span soft-inplane tihrotor model with an elastic wing. Parametric effects of the lag stiffness of blades and the flight speed are analyzed. Numerical simulations demonstrate that the multibody analytical model can analyze the aeroelastic stability of the tiltrotor aircraft in the helicopter mode.展开更多
This article presents a new mathematical model for helicopter comprehensive analysis with the features of flexibility and mathematical simplicity. The model synthesizes the rigid fuselage motion model with 6 degrees o...This article presents a new mathematical model for helicopter comprehensive analysis with the features of flexibility and mathematical simplicity. The model synthesizes the rigid fuselage motion model with 6 degrees of freedom,coupled flap-lag-torsion elastic rotor blade motion model,unsteady aerodynamics model with dynamic stall and high order generalized dynamic wake model. A new blade structural operator with implicit form is formulated,and the components of the blade structure model are independent of each other so that it is convenient to change or handle any component of blade structure without changing the others. What is more,the entire model is developed in a strict state-space form to simplify the comprehensive analysis. Finally,the UH-60 helicopter is taken as an example to predict the blade natural characteristics,the trim characteristics including controls and fuselage attitudes as well as the airloads at blade section under the flight conditions of high speed with moderate thrust and high thrust with moderate speed. The results are compared with UH-60 flight test data and those predicted by two well-known comprehensive codes. The validity of the model presented in this article is verified.展开更多
The particularity and practicality of harmony operations of close-coupling multiple helicopters indicate that the researches on it are urgent and necessary, Using the model that describes two hovering helicopters carr...The particularity and practicality of harmony operations of close-coupling multiple helicopters indicate that the researches on it are urgent and necessary, Using the model that describes two hovering helicopters carrying one heavy load, an inertia coordinate system and body coordinate systems of each sub-system are established. A nonlinear force model is established too. The equilibrium computation results can be regarded as the reference control inputs of the flight control system under hovering or low-speed flight condition. After the establishment of a translation kinematics model and a posture kinematics model, a coupling dynamics model of the multiple helicopter system is set up. The results can also be regarded as the base to analyze stabilization and design a controller for a close-coupling multiple helicopters harmony operation system.展开更多
基金supported by the Aeronautical Science Foundation of China(Nos.20220058052002,20240007052001)。
文摘In this paper,a practical method named linear active disturbance rejection control(LADRC)with adaptive tuning is proposed for attitude control of small-scale unmanned helicopter.The proposed method accounts for both external disturbances and internal dynamic uncertainties,as well as parameter deviations arising from parameter uncertainty,while maintaining a relatively small number of adjustable parameters.Furthermore,it addresses the limitation that conventional active disturbance rejection control methods cannot be rigorously analyzed for stability.The total disturbance of unmanned helicopter is estimated and compensated by designed LADRC.The introduction of adaptive control realizes online parameter tuning,which eliminates parameter deviation and further improves control precision.Moreover,it also provides a novel idea to prove the stability of controller,so that it can be analyzed by Lyapunov function.Finally,the anti-disturbance performance and effectiveness of proposed method are verified by numerical simulation.
基金supported by the National Natural Science Foundation of China(No.11602200)。
文摘This study is dedicated to numerically investigate the dynamic behavior of a missile released from a helicopter under the influence of downwash from the rotating rotors using AGM-114 Hellfire and UH-60 as the testcase.Simulations are conducted using unsteady Reynolds-averaged Navier-Stokes(URANS)with shear stress transport(SST)k-ωturbulence model,incorporating six-degree-of-freedom(6-DOF)motion and overset grid.Two releasing scenarios,viz.,hover and forward flight,are analyzed under varying missile launch thrust and helicopter forward flight speed.Results reveal that the rotor downwash significantly affects the stability of the missile,particularly during hovering case,where low thrust prolongs wake interaction.In forward flight,the increased airspeed can in principle reduce wake influence but introduces asymmetrical aerodynamic effects on the trajectory of the missile.The findings offer guidance for missile release and launch planning in rotorcraft operations.
基金the Office of Naval Research,ONR,under Grant/Contract numbers N00014-14-C-0020(PSU)and N00014-13-C-0456(CRAFT Tech).
文摘This study presents the development of computationally efficient coupling of Navier–Stokes Computational Fluid Dynamics(CFD)with a helicopter flight dynamics model with the ultimate goal of real-time simulation of airwake effects in the helicopter/ship Dynamic Interface(DI).The flight dynamics model is free to move within a computational domain,where the main rotor forces are converted to source terms in the momentum equations of the CFD solution using an actuator disk model.Simultaneously,the CFD solver calculates induced velocities that are fed back to the simulation and affect the aerodynamic loads in the flight dynamics.The CFD solver models the inflow,ground effect and interactional aerodynamics in the flight dynamics simulation,and these calculations can be coupled with the solution of the external flow(e.g.,ship airwake effects).The simulation framework for fully-coupled pilot-in-the-loop(PIL)flight dynamics/CFD is demonstrated for a simplified shedding wake.Initial tests were performed with 0.38 million structured grid cells running on 352 processors and showed near-real-time performance.Improvements to the coupling interface are described that allow the simulation run at near-real-time execution speeds on currently available computing platforms.Improvements in computing hardware are expected to allow real-time simulations.
基金supported by the Fundamental Research Funds for the Central Universities (No. NS2018007)
文摘A numerical study on flow control of ship airwake during shipboard landing is carried out to address the effect of flow control devices on helicopter rotor airload. The in-house Reynolds Averaged Navier-Stokes(RANS) based solver Rotorcraft AeroDynamics and Aeroacoustics Solver(RADAS), with combination of momentum source approach is employed to conduct the helicopter shipboard landing simulation. The control effects of three aerodynamic modifications of ship superstructure, i.e. ramp, notch and flap, in different Wind-Over-Deck(WOD) conditions are discussed.From the steady simulation results, the effect of spatial variation of ship airwake on rotor airloads is concluded. The aerodynamic modifications reduce the strength of shedding vortex and increase rotor normal force through delaying and relieving flow separation, and therefore are beneficial to alleviate the limitation of control inputs. By contrast, the perturbation of unsteady ship airwake can cause the serious oscillation of rotor forces during shipboard landing. The unsteady simulations show that the turbulence intensity of ship airwake and oscillatory rotor airloading, represented by Root-Mean-Square(RMS) loading, can be remarkably reduced by the ramp and notch modifications, while the flap modification has adverse effect. It means that flow control devices have large potential benefits to alleviate the pilot's workload and improve the shipboard landing safety, but they should be well designed to avoid the introduction of more vortex, which leads to increase in disturbance of flow field.
基金the funding provided by the National Helicopter Development Project of China。
文摘Accurate measurement of helicopter rotor motion parameters(flap,lead-lag,torsion,and azimuth angles)is essential for rotor blade design,helicopter dynamics modeling,and flight safety and health monitoring.However,the existing methods face challenges in testing equipment installation,calibration,and data transmission,resulting in limited reports on real-time in-flight measurements of blade motion parameters.This paper proposes a non-contact optoelectronic method based on two-dimensional position-sensitive detectors for in-flight measurement and a ground calibration system to obtain real-time rotor motion parameters during helicopter flight.The proposed method establishes the time evolution relationship of rotor motion parameters and verifies the performance of the in-flight measurement system regarding measurement resolution and accuracy through the construction of a blade motion posture experimental platform.The proposed method has been applied to the flight measurement of a medium-sized single-rotor helicopter,and the obtained results have been compared with theoretical analysis outcomes.Furthermore,this paper examines the characteristics of blade motion parameters during flight and discusses the challenges and potential solutions for measuring rotor motion parameters during helicopter flight using the proposed method.
文摘Airborne landing with shipboard helicopters gradually replaces surface landing to dominate joint amphibious operations.A problem with shipboard helicopter mission planning is conducted in the context of amphibious operations.First,the typical missions of shipborne helicopters in amphibious operations are analyzed.An Amphibious Operational Mission Planning Model for Shipboard Helicopters(AOMPMSH)is established,with the objectives of minimizing the completion time of the amphibious campaign and minimizing troop and helicopter losses,taking the available operational resources and the order of the mission sub-phases into account.Then,a simulationbased amphibious operations effectiveness assessment model is constructed to calculate the optimization objectives of AOMPMSH by simulating the campaign development with an amphibious objective area situation transfer model and simulating the engagement process with a modified Lanchester model.A reference point based multi-objective optimization algorithm is designed to solve the proposed AOMPMSH.The population iteration mechanism employs an initial population generation method and a local search method to solve the problem of vast definition space.The population ranking selection mechanism employs a population distribution based reference point generation method to solve the problem of population irregular distribution.Finally,a simulation case with the background of a battalion-scaled amphibious campaign is presented.The calculation results verify the rationality of the proposed model and the superiority of the designed algorithm and have some reference value for the operational applications of shipboard helicopters in amphibious operations.
文摘The general structure of ship-borne helicopter landing forecast system is presented, and a novel ship motion prediction model based on minor component analysis (MCA) is built up to improve the forecast effectiveness. To validate the feasibility of this landing forecast system, time series for the roll, pitch and heave are generated by simulation and then forecasted based on MCA. Simulation results show that ship-borne helicopters can land safely in higher sea condition while carrying on rescue or replenishment tasks at sea in terms of the landing forecast system.
基金co-supported by the National Natural Science Foundation of China(No.52275061)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(No.KYCX24_0562)。
文摘The ballistic impact identification method for the helicopter Tail Drive Shaft System(TDSS)isn't yet comprehensive,which affects helicopter flight safety.This paper proposes a ballistic impact identification method for the TDSS based on vibration response analysis.Based on the Johnson-Cook constitutive model and failure criteria,the ballistic impact finite element simulation model is established,which is verified by the ballistic impact experiment of the Tail Drive Shaft(TDS).Considering the ballistic impact excitation force,the dynamic model of the TDSS with ballistic impact is established,which is verified by finite element commercial software.If a bullet hits the TDS,the bending vibration displacement increases sharply at a certain moment and then significantly increases but remains stable.Meanwhile,the critical speed component appears in the frequency-domain response of bending vibration,and then the speed component significantly increases but remains stable.What's more,the axis trajectory exhibits a sudden,large-scale,and irregular whirling motion at a certain moment,followed by a significant increase but remains stable.Furthermore,if the axial vibration response is small,the bullet core shooting should be considered vertically or at a small incident angle,otherwise,it should be considered at a large incident angle.
基金funded by the National Natural Science Foundation of China(No.52105060)the Special Transmission Project,China(No.KY-1044-2023-0458)。
文摘To reduce the vibration of the Coaxial Helicopter Main Transmission System(CHMTS)considering both level and vertical flight conditions,a vibration evaluation and optimization model for the CHMTS was built.The vibration simulation model of the CHMTS was set up by gear dynamics theory and loaded contact analysis.For better evaluation of the system vibration,a vibration evaluation method for the CHMTS was established by the G1 method-variation coefficient method.A hybrid Gravitational Search Algorithm-Simulated Annealing(GSA-SA)algorithm was combined to balance convergence speed and searching accuracy.The principle test was conducted to prove the accuracy of theoretical method,in which the maximum relative error is16.26%.The optional results show that the vibration of the optimized transmission system decreases significantly,in which the maximum reduction of key vibration indicators reaches more than 20%.The theoretical results have been compared to the experiment to verify the effectiveness of the vibration optimization method.The proposed method could be extended to other fields.
基金the Natural Science Foundation of Sichuan Province,China(Nos.2023NSFSC0902,2024ZYD0083)the Open Project of Key Laboratory of Aerodynamic Noise Control of China Aerodynamics Research and Development Center(No.ANCL20220202)+1 种基金the Open Project of Key Laboratory of Flight Techniques and Flight Safety,CAAC,China(No.FZ2022KF01)the Fundamental Research Funds for the Central Universities,China(No.24CAFUC01007)。
文摘This paper presents a comprehensive test and systematic evaluation analysis of cabin noise in the Robinson R44 RAVEN II helicopter.Initially,microphones were placed within the cabin to conduct systematic assessments of noise levels under various flight conditions,including takeoff,climbing,level flight,landing,hovering,etc.Subsequently,time–frequency analysis was conducted on the test data utilizing traditional A-weighted sound pressure levels,which was followed by quantitative comparisons across different flight conditions.Then,detailed evaluation and discussion were conducted,taking into account the subjective perceptions and communication challenges of cabin crew members.This assessment incorporated the use of aviation noise indicators,speech interference levels,and metrics related to sound quality.Finally,potential noise reduction measures and their effects were preliminarily discussed.The results indicate that helicopter cabin noise exhibited variations across different flight states or positions within the same state,ranging from 87.6 d B(A)to 92.6 dB(A).Discrepancies between A-weighted sound pressure level and psychoacoustic parameters were observed,particularly during hovering states,which indicate that there is a necessity for the combination of multiple evaluation indicators.Notably,damping measure can serve as a pivotal factor in mitigating cabin noise.
基金supported by the Aviation Science Fund(20145784010)
文摘For the research of helicopter/ship dynamic interface,the method of combining steady flow and stochastic flow is adopted to establish a flow field model applied to the flight dynamics analysis of shipborne helicopter.The steady flow is calculated by computational fluid dynamics(CFD)method,while the stochastic flow is composed of the compensation velocity derived from ship motion and turbulence above the deck.The accuracy of the proposed flow field model is verified by comparing the helicopter response in the proposed flow field with the results calculated by US Army′s Military Specifications(MIL)model which is commonly used in engineering.Meanwhile,it also shows the proposed flow field model is more appliable to flight dynamics analysis of shipborne helicopter.On that the basis,ship deck flow field is simulated at different sea conditions by adjusting the wind speed on the deck,mother ship movement and shipboard turbulence,etc.And helicopter angular rate response is calculated.The results show that the difference of dynamic stability between helicopter′s roll and pitch leads to the facts that the influence of above factors on the helicopter′s roll angular rate response is greater than that of pitch angular rate,that the frequency and amplitude of mother ship roll motion are much greater than those of pitch motion,and that the disturbance caused by roll motion on the air has greater influence on the helicopter response.The shipboard turbulence is the main disturbance factor that influences helicopter flight stability and its intensity determines the amplitudes of angular rate response.
基金co-supported by the Foundation of the State Key Laboratory of Aerodynamics(No.RAL202203)the National Key Laboratory Foundation(No.6142202202)the China Postdoctoral Science Foundation(No.2024M754133)。
文摘An advanced Actuator Surface Method(ASM)coupled with Computational Fluid Dynamics(CFD)is developed and applied to the complex unsteady aerodynamic simulation of helicopter.By introducing an improved three-dimensional anisotropic Gaussian kernel,this method effectively addresses the severe aerodynamic load fluctuations commonly associated with traditional Virtual Blade Method(VBM)due to turbulent flow around blade elements.To manage the issues of regional shape and grid cell quantity variations caused by virtual blade sweeping,a universal hybrid grid generation strategy is established without body-fitted and disk interpolation grids,which enhances the computational stability at both blade elements and blade edges.Aerodynamic numerical simulations of helicopter are performed using this method,focusing on rotor/fuselage interaction dominated by rotor wake motion and fuselage blockage effects,Blade-Vortex Interaction(BVI)induced by tip vortices,and maneuvering flights involving collective pitch ramp increases.The results indicate that the advanced ASM demonstrates reliability and robustness in the simulation of complex unsteady flow fields around helicopter.Under similar computational accuracy,the advanced ASM improves computational efficiency by nearly 40 times compared to the oversetgrid-based full Blade-Resolved(B-R)method,and by 6 times compared to the VBM.It shows significant advantages when applied to complex full-aircraft interaction and maneuvering flight conditions that require substantial computational resources.
基金support of the National Natural Science Foundation of China(No.12032012)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China。
文摘To achieve high-precision trajectory following during helicopter maneuver tasks and reduce the disruptive influences of unknown variabilities,this study introduces a cascaded-loop helicopter trajectory tracking controller,whose parameters are set using an Ant Colony OptimizationSlime Mould Algorithm(ACO-SMA).Initially,a nonlinear flight dynamics model of the helicopter is constructed.Observer gain functions and nonlinear feedback from a vibrational suppression function to improve the tracking performance of the controller,addressing issues in disturbance estimation and compensation of the Active Disturbance Rejection Control(ADRC).Simultaneously,a cascaded loop system,comprising an internal attitude loop and an external position loop,is created,and the ant colony-slime mold hybrid algorithm optimizes the system parameters of the trajectory tracking controller.Finally,helicopter trajectory tracking simulation experiments are conducted,including spiral ascending and“8”shape climbing maneuvers.The findings indicate that the ADRC employed for helicopter trajectory tracking exhibits outstanding performance in rejecting disturbances caused by gusts and accurately tracking trajectories.The trajectory tracking controller,whose parameters are optimized by the ACO-SMA,shows higher tracking precision compared to the conventional PID and ADRC,thereby substantially improving the precision of maneuver tasks.
基金supported by the National Key R&D Program of China(No.2022YFC3701500)the Key R&D Plan Projects of Zhejiang Province(No.2024SSYS0072)Zhejiang Provincial Natural Science Foundation(No.LDT23E0601).
文摘Ship operations are crucial to global trade,and their decarbonization is essential to mitigate climate change.This study evaluates the economic viability of existing and emerging decarbonization technologies in maritime shipping using the levelized cost of energy methodology.It includes a detailed comparative analysis based on essential criteria and sensitivity assessments to highlight the economic impacts of technological advancements.Key factors influencing total costs include fuel costs,carbon pricing,and energy demands for carbon capture.The findings reveal that methanol is more cost-effective than heavy fuel oil(HFO)when priced below 3000 CNY/t,assuming HFO costs 4400 CNY/t.Additionally,methanol with post-combustion carbon capture is less expensive than pre-combustion carbon capture.When carbon prices rise above 480 CNY/t,carbon capture technologies prove more economical than purchasing carbon emission allowances for HFO and liquefied natural gas.Enhanc-ing the use of exhaust gas waste heat is recommended for cost savings.Post-combustion carbon capture also shows greater efficiency,requiring about 1.1 GJ/t less energy than pre-combustion methods,leading to lower overall costs.Future research should focus on market mechanisms to stabilize fuel prices and develop less energy-intensive carbon capture technologies.This study offers critical insights into effective decarbonization strategies for advancing global maritime trade in the present and future.
文摘At Yangpu Port on the northwestern tip of Hainan Island,towering quay cranes are lined in neat rows, hoisting containers on and off cargo vessels in constant motion.“Today, half of the international ships we pilot are ultra-large vessels over 200meters in length,” said Lin Hongpin,head of the Yangpu branch of Hainan Provincial Ship Pilot Station. Since the launch of the island-wide special customs operations, port throughput has continued to climb, with pilotage services for such large ships rising by nearly 20 percent year on year.
文摘An experimental study of the flow in a helicopter inlet with front output shaft and partial flow dynamic head is conducted in low speed wind tunnel. The flow characters of the inlet in the range of the yaw angle from 0~135°are presented in this paper. The static pressure distributions along the duct, distortions of the flow field at the outlet section and total pressure recovery coefficients are measured and analyzed. The results show that this type of inlet has high total pressure recovery coefficients at a wide range of yaw angle. The regions of local flow separation and distortion are closely related to the yaw angle. It′s also found that the outlet section has the best characteristics at sideslip, and sharply deteriorated characteristics at the yawed flight with a yaw angle of more than 90°
文摘The muhi-body analysis of the aeroelastic stability of the tiltrotor aircraft is presented. Muhi-body dynamic differential equations are combined with the equations of the unsteady dynamic inflow model to establish the complete unsteadily aeroelastic coupling analytical model of the tiltrotor. The stability of the tiltrotor in the helicopter mode is analyzed aiming at a semi span soft-inplane tihrotor model with an elastic wing. Parametric effects of the lag stiffness of blades and the flight speed are analyzed. Numerical simulations demonstrate that the multibody analytical model can analyze the aeroelastic stability of the tiltrotor aircraft in the helicopter mode.
文摘This article presents a new mathematical model for helicopter comprehensive analysis with the features of flexibility and mathematical simplicity. The model synthesizes the rigid fuselage motion model with 6 degrees of freedom,coupled flap-lag-torsion elastic rotor blade motion model,unsteady aerodynamics model with dynamic stall and high order generalized dynamic wake model. A new blade structural operator with implicit form is formulated,and the components of the blade structure model are independent of each other so that it is convenient to change or handle any component of blade structure without changing the others. What is more,the entire model is developed in a strict state-space form to simplify the comprehensive analysis. Finally,the UH-60 helicopter is taken as an example to predict the blade natural characteristics,the trim characteristics including controls and fuselage attitudes as well as the airloads at blade section under the flight conditions of high speed with moderate thrust and high thrust with moderate speed. The results are compared with UH-60 flight test data and those predicted by two well-known comprehensive codes. The validity of the model presented in this article is verified.
基金National Natural Science Foundation of China(60475039)
文摘The particularity and practicality of harmony operations of close-coupling multiple helicopters indicate that the researches on it are urgent and necessary, Using the model that describes two hovering helicopters carrying one heavy load, an inertia coordinate system and body coordinate systems of each sub-system are established. A nonlinear force model is established too. The equilibrium computation results can be regarded as the reference control inputs of the flight control system under hovering or low-speed flight condition. After the establishment of a translation kinematics model and a posture kinematics model, a coupling dynamics model of the multiple helicopter system is set up. The results can also be regarded as the base to analyze stabilization and design a controller for a close-coupling multiple helicopters harmony operation system.
