Analysis of rotorcraft dynamics requires solution of the rotor induced flow field.Often,the appropriate model to be used for induced flow is nonlinear potential flow theory（which is the basis of vortex-lattice method...Analysis of rotorcraft dynamics requires solution of the rotor induced flow field.Often,the appropriate model to be used for induced flow is nonlinear potential flow theory（which is the basis of vortex-lattice methods）.These nonlinear potential flow equations sometimes must be solved in real time––such as for real-time flight simulation,when observers are needed for controllers,or in preliminary design computations.In this paper,the major effects of nonlinearities on induced flow are studied for lifting rotors in low-speed flight and hover.The approach is to use a nonlinear statespace model of the induced flow based on a Galerkin treatment of the potential flow equations.展开更多
An exhaustive study of the noncontinuous-state laser dynamics associated with the transient optical process is significant because it reveals the complex physical mechanisms and characteristics in nonlinear laser syst...An exhaustive study of the noncontinuous-state laser dynamics associated with the transient optical process is significant because it reveals the complex physical mechanisms and characteristics in nonlinear laser systems.In this study,in-depth theoretical interpretation and experimental verification of the noncontinuous-state dynamics in laser system are presented,based on developed pulse-modulated frequency-shifted laser feedback interferometry(LFI).By introducing external pulse modulation,we investigate the nonlinear time-of-flight dynamics and related photon behaviors evolution of the pulsed LFI system by observing the changes in effective interference time sequences for interference realization and attainable minimum feedback photon number of the signal under various modulated noncontinuous states.Implementation of the pulse-modulated LFI scheme should exceed the pulse overlapping time window limit of 1.93μs to effectively extract and preserve the extracavity feedback photon information.Experiments reveal that the minimum feedback photon number of signals successfully measured by the pulsed LFI sensor is 0.067 feedback photons per Doppler cycle,exhibiting high sensitivity for extremely weak signal detection.Further,simultaneous measurement for velocity and distance of the moving object is performed to validate the feasibility and applicability of the pulsed LFI.The system can successfully achieve large-range simultaneous measurements within the velocity range of 73.5-612.6 mm∕s,over a distance of 25.5 km.This work opens the way to unexplored frontiers of pulsed LFI to fill the research gap in noncontinuous laser dynamics in this field,showcasing diverse and wide-ranging applications in the realm of integrated sensing,remote monitoring,and positioning and navigation.展开更多
基金co-supported by the National Natural Science Foundation of China(No.51375104)the Heilongjiang Province Funds for Distinguished Young Scientists(No.JC201405)+1 种基金the China Postdoctoral Science Foundation(No.2015M581433)the Postdoctoral Science Foundation of Heilongjiang Province(No.LBH-Z15038)
文摘Analysis of rotorcraft dynamics requires solution of the rotor induced flow field.Often,the appropriate model to be used for induced flow is nonlinear potential flow theory（which is the basis of vortex-lattice methods）.These nonlinear potential flow equations sometimes must be solved in real time––such as for real-time flight simulation,when observers are needed for controllers,or in preliminary design computations.In this paper,the major effects of nonlinearities on induced flow are studied for lifting rotors in low-speed flight and hover.The approach is to use a nonlinear statespace model of the induced flow based on a Galerkin treatment of the potential flow equations.
基金National Natural Science Foundation of China(62275001,62105001)China Postdoctoral Science Foundation(GZC20242187)Zhejiang Province Postdoctoral Research Funding(ZJ2024097)。
文摘An exhaustive study of the noncontinuous-state laser dynamics associated with the transient optical process is significant because it reveals the complex physical mechanisms and characteristics in nonlinear laser systems.In this study,in-depth theoretical interpretation and experimental verification of the noncontinuous-state dynamics in laser system are presented,based on developed pulse-modulated frequency-shifted laser feedback interferometry(LFI).By introducing external pulse modulation,we investigate the nonlinear time-of-flight dynamics and related photon behaviors evolution of the pulsed LFI system by observing the changes in effective interference time sequences for interference realization and attainable minimum feedback photon number of the signal under various modulated noncontinuous states.Implementation of the pulse-modulated LFI scheme should exceed the pulse overlapping time window limit of 1.93μs to effectively extract and preserve the extracavity feedback photon information.Experiments reveal that the minimum feedback photon number of signals successfully measured by the pulsed LFI sensor is 0.067 feedback photons per Doppler cycle,exhibiting high sensitivity for extremely weak signal detection.Further,simultaneous measurement for velocity and distance of the moving object is performed to validate the feasibility and applicability of the pulsed LFI.The system can successfully achieve large-range simultaneous measurements within the velocity range of 73.5-612.6 mm∕s,over a distance of 25.5 km.This work opens the way to unexplored frontiers of pulsed LFI to fill the research gap in noncontinuous laser dynamics in this field,showcasing diverse and wide-ranging applications in the realm of integrated sensing,remote monitoring,and positioning and navigation.
