The flight control systems, designed in order to assure the necessary safety level even in failure conditions, are generally characterized by a proper redundant layout. The redundancies must be designed in order to as...The flight control systems, designed in order to assure the necessary safety level even in failure conditions, are generally characterized by a proper redundant layout. The redundancies must be designed in order to assure an adequate system behavior when some failures are present; in fact an incorrect layout may cause serious shortcomings concerning the response when some component is not operational. Therefore the usual correct design activities request the complete analysis of the system behavior in failure condition. The work analyses the response of a redundant secondary flight control hydraulic servo-mechanism equipped with some proper equalization devices, when some of the most probable and representative failures are present. It must be noted that the redundancy layout, designed in order to assure the necessary safety level even in failure conditions, may behave improperly during normal operations, if the system architecture is unsuitable, when manufacturing defects are present. The improper behavior, generally consisting of force fighting or speed fighting caused by different offsets or asymmetries between the two sections of the system, may be usually overcome by means of a suitable equalization device. Therefore, the system behavior during and following the failure transient greatly depends on both its redundancy architecture and related equalization device. The above mentioned problems have been studied by means of an appropriate physical-mathematical model of a typical electro-hydraulic servo-mechanism prepared to the purpose, performing a certain number of simulations of representative actuations in which different types of failures are accurately modeled. In the opinion of the authors, this paper concerns a topic quite neglected but important in the technical literature. At the best of the authors＇ knowledge, no specific scientific work in this field is available, excepting some industrial technical reports.展开更多
In order to investigate the effects of vortex control by deflecting flaps on the improvement of the aerodynamics of highly swept wings at large incidence, comparison of the experimental and numerical studies was condu...In order to investigate the effects of vortex control by deflecting flaps on the improvement of the aerodynamics of highly swept wings at large incidence, comparison of the experimental and numerical studies was conducted for a 74° delta wing equipped with an apex flap and leading edge flaps. In the experimental study, flow visualization and force measurement were employed and in the numerical study the pseudo compressibility method was utilized to solve the 3 D incompressible Navier Stokes equations. The flow visualization and numerical simulation show that two vortex systems generated on the apex flap and leading edge flaps interact in the form of mergence, and the downward deflection of the apex flap enhances the strength and delays the breakdown of the prime vortex at large incidence. The comparison of the aerodynamic characteristics illustrates that there are advantageous effects of deflecting flaps downward on the control of vortices.展开更多
Based on the Theodorsen’s Theory of the aerodynamic forces on wing-aileron, the Scanlan’s Theory is expanded considering a deck-flap system. It is suggested that a new forced vibration method can acquire aerodynamic...Based on the Theodorsen’s Theory of the aerodynamic forces on wing-aileron, the Scanlan’s Theory is expanded considering a deck-flap system. It is suggested that a new forced vibration method can acquire aerodynamic derivatives of this deck-flap system theoretically. After obtaining the wind induced forces, a deck-flap equation of motion in time domain is established to investigate its control law. Numerical simulation results indicate suboptimal control law of the deck-flap system can suppress the flutter effectively, and the flutter speed can be increased for desirable purpose.展开更多
扑翼飞行器通过模仿昆虫及鸟类的扑翼运动,在低雷诺数环境下具有优异的气动效率和机动性。而扑旋翼飞行器在扑翼运动的基础上实现了机翼的被动旋转运动,具备更好的悬停及垂直起降能力,是近些年新兴的研究热点。本文系统综述了扑翼微型...扑翼飞行器通过模仿昆虫及鸟类的扑翼运动,在低雷诺数环境下具有优异的气动效率和机动性。而扑旋翼飞行器在扑翼运动的基础上实现了机翼的被动旋转运动,具备更好的悬停及垂直起降能力,是近些年新兴的研究热点。本文系统综述了扑翼微型飞行器(Flapping‑wing micro air vehicles,FWMAVs)及扑旋翼微型飞行器(Flapping‑wing rotor micro air vehicles,FWRMAVs)在系统建模与控制方法方面近几年的研究进展,分析了仿昆虫扑翼飞行机理中的非定常空气动力学理论,并探讨了已有的基于仿昆虫的FWMAVs及FWRMAVs系统建模及控制方法。最后,提出了目前FWMAVs在飞行动力学和控制方法上面临的柔性翼气动力建模和非定常扰动抑制等问题,分析了FWRMAVs缺乏对其飞行动力学特性和主动姿态控制等方面研究的问题,同时本文对该领域未来进一步的研究做出了展望。展开更多
文摘The flight control systems, designed in order to assure the necessary safety level even in failure conditions, are generally characterized by a proper redundant layout. The redundancies must be designed in order to assure an adequate system behavior when some failures are present; in fact an incorrect layout may cause serious shortcomings concerning the response when some component is not operational. Therefore the usual correct design activities request the complete analysis of the system behavior in failure condition. The work analyses the response of a redundant secondary flight control hydraulic servo-mechanism equipped with some proper equalization devices, when some of the most probable and representative failures are present. It must be noted that the redundancy layout, designed in order to assure the necessary safety level even in failure conditions, may behave improperly during normal operations, if the system architecture is unsuitable, when manufacturing defects are present. The improper behavior, generally consisting of force fighting or speed fighting caused by different offsets or asymmetries between the two sections of the system, may be usually overcome by means of a suitable equalization device. Therefore, the system behavior during and following the failure transient greatly depends on both its redundancy architecture and related equalization device. The above mentioned problems have been studied by means of an appropriate physical-mathematical model of a typical electro-hydraulic servo-mechanism prepared to the purpose, performing a certain number of simulations of representative actuations in which different types of failures are accurately modeled. In the opinion of the authors, this paper concerns a topic quite neglected but important in the technical literature. At the best of the authors＇ knowledge, no specific scientific work in this field is available, excepting some industrial technical reports.
文摘In order to investigate the effects of vortex control by deflecting flaps on the improvement of the aerodynamics of highly swept wings at large incidence, comparison of the experimental and numerical studies was conducted for a 74° delta wing equipped with an apex flap and leading edge flaps. In the experimental study, flow visualization and force measurement were employed and in the numerical study the pseudo compressibility method was utilized to solve the 3 D incompressible Navier Stokes equations. The flow visualization and numerical simulation show that two vortex systems generated on the apex flap and leading edge flaps interact in the form of mergence, and the downward deflection of the apex flap enhances the strength and delays the breakdown of the prime vortex at large incidence. The comparison of the aerodynamic characteristics illustrates that there are advantageous effects of deflecting flaps downward on the control of vortices.
文摘Based on the Theodorsen’s Theory of the aerodynamic forces on wing-aileron, the Scanlan’s Theory is expanded considering a deck-flap system. It is suggested that a new forced vibration method can acquire aerodynamic derivatives of this deck-flap system theoretically. After obtaining the wind induced forces, a deck-flap equation of motion in time domain is established to investigate its control law. Numerical simulation results indicate suboptimal control law of the deck-flap system can suppress the flutter effectively, and the flutter speed can be increased for desirable purpose.
文摘扑翼飞行器通过模仿昆虫及鸟类的扑翼运动,在低雷诺数环境下具有优异的气动效率和机动性。而扑旋翼飞行器在扑翼运动的基础上实现了机翼的被动旋转运动,具备更好的悬停及垂直起降能力,是近些年新兴的研究热点。本文系统综述了扑翼微型飞行器(Flapping‑wing micro air vehicles,FWMAVs)及扑旋翼微型飞行器(Flapping‑wing rotor micro air vehicles,FWRMAVs)在系统建模与控制方法方面近几年的研究进展,分析了仿昆虫扑翼飞行机理中的非定常空气动力学理论,并探讨了已有的基于仿昆虫的FWMAVs及FWRMAVs系统建模及控制方法。最后,提出了目前FWMAVs在飞行动力学和控制方法上面临的柔性翼气动力建模和非定常扰动抑制等问题,分析了FWRMAVs缺乏对其飞行动力学特性和主动姿态控制等方面研究的问题,同时本文对该领域未来进一步的研究做出了展望。
