A new landing region selection algorithm for an unmanned helicopter is proposed based on an attention model.Different from the original attention model,some properties of the possible safe landing regions（e.g.,depth,...A new landing region selection algorithm for an unmanned helicopter is proposed based on an attention model.Different from the original attention model,some properties of the possible safe landing regions（e.g.,depth,regional color and motion features）are included in the selection algorithm.Furthermore,regional color and motion features are fused directly into the saliency map because these features do not have the ＂central-peripheral＂property.Experimental results validate the feasibility and efficiency of this approach.展开更多
Unmanned helicopters equipped with adaptive landing gear will dramatically extend their application especially in dealing with challenging terrains.This study presents a novel cable-driven legged landing gear(CLG)with...Unmanned helicopters equipped with adaptive landing gear will dramatically extend their application especially in dealing with challenging terrains.This study presents a novel cable-driven legged landing gear(CLG)with differential transmission for unmanned helicopters in complex landing environments.To obtain the preferred configuration of the legged mechanism,a multi-objective optimization framework for the CLG is constructed by concurrently considering terrain adaptability,landing stability and reasonable linkage of internal forces.The non-dominated sorting genetic algorithmⅡis employed to numerically acquire the optimal scale parameters that guide the mechanical design of the CLG.An unmanned helicopter prototype equipped with the devised CLG is developed with key performance assessment.Experimental results show that the devised CLG can provide energy-efficient support over uneven terrains(totally driven torque demand less than 0.1 N m)in quasi-static landing tests,and favorable terrain adaptability(posture fluctuation of the fuselage less than±1°)in unknown slope landing tests.These exhibited merits give the proposed CLG the potential to enhance the landing performance of future aircraft in extreme environments.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
针对直升机着舰过程中的下滑进场环节,从流场环境对直升机飞行品质影响的角度出发,研究了直升机着舰策略。分析了下滑进场区域的流场分布,研究表明流场的分布与距离甲板的高度相关,高度越低,气流速度均值越大,且下洗气流主要集中在迎甲...针对直升机着舰过程中的下滑进场环节,从流场环境对直升机飞行品质影响的角度出发,研究了直升机着舰策略。分析了下滑进场区域的流场分布,研究表明流场的分布与距离甲板的高度相关,高度越低,气流速度均值越大,且下洗气流主要集中在迎甲板风方向的路线区域,对直升机的飞行品质造成影响。分析了不同甲板风(Wind on deck,WOD)条件下直升机平衡状态量,分别从旋翼所需功率、操纵量和机体姿态等方面对进场方式进行了研究,表明合理的进场方式有利于着舰安全。展开更多
基金Supported by Aeronautical Science Foundation of China(20130542025)
文摘A new landing region selection algorithm for an unmanned helicopter is proposed based on an attention model.Different from the original attention model,some properties of the possible safe landing regions（e.g.,depth,regional color and motion features）are included in the selection algorithm.Furthermore,regional color and motion features are fused directly into the saliency map because these features do not have the ＂central-peripheral＂property.Experimental results validate the feasibility and efficiency of this approach.
基金supported by the National Natural Science Foundation of China(Grant No.52175011)。
文摘Unmanned helicopters equipped with adaptive landing gear will dramatically extend their application especially in dealing with challenging terrains.This study presents a novel cable-driven legged landing gear(CLG)with differential transmission for unmanned helicopters in complex landing environments.To obtain the preferred configuration of the legged mechanism,a multi-objective optimization framework for the CLG is constructed by concurrently considering terrain adaptability,landing stability and reasonable linkage of internal forces.The non-dominated sorting genetic algorithmⅡis employed to numerically acquire the optimal scale parameters that guide the mechanical design of the CLG.An unmanned helicopter prototype equipped with the devised CLG is developed with key performance assessment.Experimental results show that the devised CLG can provide energy-efficient support over uneven terrains(totally driven torque demand less than 0.1 N m)in quasi-static landing tests,and favorable terrain adaptability(posture fluctuation of the fuselage less than±1°)in unknown slope landing tests.These exhibited merits give the proposed CLG the potential to enhance the landing performance of future aircraft in extreme environments.
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.
文摘针对直升机着舰过程中的下滑进场环节,从流场环境对直升机飞行品质影响的角度出发,研究了直升机着舰策略。分析了下滑进场区域的流场分布,研究表明流场的分布与距离甲板的高度相关,高度越低,气流速度均值越大,且下洗气流主要集中在迎甲板风方向的路线区域,对直升机的飞行品质造成影响。分析了不同甲板风(Wind on deck,WOD)条件下直升机平衡状态量,分别从旋翼所需功率、操纵量和机体姿态等方面对进场方式进行了研究,表明合理的进场方式有利于着舰安全。
