Roll-isolation is an effective way for spinning vehicle to greatly reduce the roll gyro range of strapdown Inertial Navigation System(SINS)and increase the accuracy of inertial navigation.However,during a recent fligh...Roll-isolation is an effective way for spinning vehicle to greatly reduce the roll gyro range of strapdown Inertial Navigation System(SINS)and increase the accuracy of inertial navigation.However,during a recent flight test,the roll-isolated control system failure was observed under a large pitch angle(706 h 685),which introduces a sharply increase in the roll angular velocity,the saturation of roll gyro and the inertial navigation failure.To address this issue,the governing equation of the roll-isolated system is derived with the consideration of various disturbance factors.The control failure is reproduced by numerical simulation.And the results show that the pitch and yaw angular velocity can cause a dramatic increase in roll rate under the large pitch angle,resulting in the roll-isolated control failure.Meanwhile,an improved roll-isolated control system is developed using PI controller,which is verified by mathematical simulation.展开更多
In this paper,a theoretical model to analyze the mode coupling induced by heat,when the fiber amplifier works at high power configuration,is proposed.The model mainly takes into consideration the mode field change due...In this paper,a theoretical model to analyze the mode coupling induced by heat,when the fiber amplifier works at high power configuration,is proposed.The model mainly takes into consideration the mode field change due to the thermally induced refractive index change and the coupling between modes.A method to predict the largest average output power of fiber is also proposed according to the mode coupling theory.The largest average output power of a large pitch fiber with a core diameter of 190 μm and an available pulse energy of 100 mJ is predicted to be 540 W,which is the highest in large mode field fibers.展开更多
A novel evaluation term and a more reasonable criterion,which is described by a new parameter of brightness factor for active large mode area fiber design,are presented.The brightness factor evaluation method is based...A novel evaluation term and a more reasonable criterion,which is described by a new parameter of brightness factor for active large mode area fiber design,are presented.The brightness factor evaluation method is based on the transverse mode competition mechanism in fiber lasers and amplifiers.The brightness factor can be seen as a description of fiber general property since it can represent the output laser brightness of the fiber laser system and because of its ability to resist the nonlinear effect.A core-doped active large pitch fiber with a core diameter of 190 μm and a mode-field diameter of180 μm is designed by this method,and the designed fiber allows effective single-mode operation.展开更多
基金co-supported by the National Science Foundation of China(No.11532002)Science Challenge Project of China(No.TZ2018001)。
文摘Roll-isolation is an effective way for spinning vehicle to greatly reduce the roll gyro range of strapdown Inertial Navigation System(SINS)and increase the accuracy of inertial navigation.However,during a recent flight test,the roll-isolated control system failure was observed under a large pitch angle(706 h 685),which introduces a sharply increase in the roll angular velocity,the saturation of roll gyro and the inertial navigation failure.To address this issue,the governing equation of the roll-isolated system is derived with the consideration of various disturbance factors.The control failure is reproduced by numerical simulation.And the results show that the pitch and yaw angular velocity can cause a dramatic increase in roll rate under the large pitch angle,resulting in the roll-isolated control failure.Meanwhile,an improved roll-isolated control system is developed using PI controller,which is verified by mathematical simulation.
基金supported by the National Natural Science Foundation of China(Grant No.61475081)
文摘In this paper,a theoretical model to analyze the mode coupling induced by heat,when the fiber amplifier works at high power configuration,is proposed.The model mainly takes into consideration the mode field change due to the thermally induced refractive index change and the coupling between modes.A method to predict the largest average output power of fiber is also proposed according to the mode coupling theory.The largest average output power of a large pitch fiber with a core diameter of 190 μm and an available pulse energy of 100 mJ is predicted to be 540 W,which is the highest in large mode field fibers.
基金supported by the National Natural Science Foundation of China(Grant No.61475081)
文摘A novel evaluation term and a more reasonable criterion,which is described by a new parameter of brightness factor for active large mode area fiber design,are presented.The brightness factor evaluation method is based on the transverse mode competition mechanism in fiber lasers and amplifiers.The brightness factor can be seen as a description of fiber general property since it can represent the output laser brightness of the fiber laser system and because of its ability to resist the nonlinear effect.A core-doped active large pitch fiber with a core diameter of 190 μm and a mode-field diameter of180 μm is designed by this method,and the designed fiber allows effective single-mode operation.
