The quantity of space debris on Earth orbit has escalated tremendously in recent years, presenting a significant hazard to human space operations. It is urgent to develop effective measures to capture and remove vario...The quantity of space debris on Earth orbit has escalated tremendously in recent years, presenting a significant hazard to human space operations. It is urgent to develop effective measures to capture and remove various space debris. For this purpose, this paper presents a tendon-actuated flexible deployable manipulator. The flexible manipulator consists of several deployable units connected by Cardan joints and actuated by tendons. Compared with the present technologies for capturing space debris such as rigid robotic arm or flying net, this flexible manipulator is deployable, reusable, lightweight and applicable to the capture of large space debris. In order to investigate its deployment dynamics, an accurate dynamic model of the flexible manipulator is established based on the natural coordinate formulation (NCF) and the absolute nodal coordinate formulation (ANCF). Subsequently, numerical simulations are carried out to study the effects of system parameters and the base satellite on its deployment dynamics. Finally, ground experiments for both deployment and bending of the flexible manipulator are conducted to verify its effectiveness and feasibility.展开更多
Spray cooling has proved its superior heat transfer performance in removing high heat flux for ground applications. However, the dissipation of vapor liquid mixture from the heat sur- face and the closed-loop circulat...Spray cooling has proved its superior heat transfer performance in removing high heat flux for ground applications. However, the dissipation of vapor liquid mixture from the heat sur- face and the closed-loop circulation of the coolant are two challenges in reduced or zero gravity space enviromnents. In this paper, an ejected spray cooling system for space closed-loop application was proposed and the negative pressure in the ejected condenser chamber was applied to sucking the two-phase mixture from the spray chamber. Its ground experimental setup was built and exper- imental investigations on the smooth circle heat surface with a diameter of 5 mm were conducted with distilled water as the coolant spraying from a nozzle of 0.51 mm orifice diameter at the inlet temperatures of 69.2 ℃ and 78.2 ℃ under the conditions of heat flux ranging from 69.76 W/cm2 to 311.45 W/cm2, volume flow through the spray nozzle varying from 11,22 L：h to 15.76 L·h. Work performance of the spray nozzle and heat transfer performance of the spray cooling system were analyzed; results show that this ejected spray cooling system has a good heat transfer performance and provides valid foundation for space closed-loop application in the near future.展开更多
In this study,a neural adaptive controller is developed for a ground experiment with a spacecraft proximity operation.As the water resistance in the experiment is highly nonlinear and can significantly affect the fide...In this study,a neural adaptive controller is developed for a ground experiment with a spacecraft proximity operation.As the water resistance in the experiment is highly nonlinear and can significantly affect the fidelity of the ground experiment,the water resistance must be estimated accurately and compensated using an active force online.For this problem,a novel control algorithm combined with Chebyshev Neural Networks(CNN)and an Active Disturbance Rejection Control(ADRC)is proposed.Specifically,the CNN algorithm is used to estimate the water resistance.The advantage of the CNN estimation is that the coefficients of the approximation can be adaptively changed to minimize the estimation error.Combined with the ADRC algorithm,the total disturbance is compensated in the experiment to improve the fidelity.The dynamic model of the spacecraft proximity maneuver in the experiment is established.The ground experiment of the proximity maneuver that considers an obstacle is provided to verify the efficiency of the proposed controller.The results demonstrate that the proposed method outperforms the pure ADRC method and can achieve close-to-real-time performance for the spacecraft proximity maneuver.展开更多
基金the National Natural Science Foundation of China(Nos.11832005,12372042,12232011)Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001)+1 种基金the Fundamental Research Funds for the Central Universities(No.NS2023002)State Key Laboratory of Mechanics and Control for Aerospace Structures(Nanjing University of Aeronautics and Astronautics)(No.MCAS-S-0223K04).
文摘The quantity of space debris on Earth orbit has escalated tremendously in recent years, presenting a significant hazard to human space operations. It is urgent to develop effective measures to capture and remove various space debris. For this purpose, this paper presents a tendon-actuated flexible deployable manipulator. The flexible manipulator consists of several deployable units connected by Cardan joints and actuated by tendons. Compared with the present technologies for capturing space debris such as rigid robotic arm or flying net, this flexible manipulator is deployable, reusable, lightweight and applicable to the capture of large space debris. In order to investigate its deployment dynamics, an accurate dynamic model of the flexible manipulator is established based on the natural coordinate formulation (NCF) and the absolute nodal coordinate formulation (ANCF). Subsequently, numerical simulations are carried out to study the effects of system parameters and the base satellite on its deployment dynamics. Finally, ground experiments for both deployment and bending of the flexible manipulator are conducted to verify its effectiveness and feasibility.
基金supported by the National Natural Science Foundation of China(No.50506003)
文摘Spray cooling has proved its superior heat transfer performance in removing high heat flux for ground applications. However, the dissipation of vapor liquid mixture from the heat sur- face and the closed-loop circulation of the coolant are two challenges in reduced or zero gravity space enviromnents. In this paper, an ejected spray cooling system for space closed-loop application was proposed and the negative pressure in the ejected condenser chamber was applied to sucking the two-phase mixture from the spray chamber. Its ground experimental setup was built and exper- imental investigations on the smooth circle heat surface with a diameter of 5 mm were conducted with distilled water as the coolant spraying from a nozzle of 0.51 mm orifice diameter at the inlet temperatures of 69.2 ℃ and 78.2 ℃ under the conditions of heat flux ranging from 69.76 W/cm2 to 311.45 W/cm2, volume flow through the spray nozzle varying from 11,22 L：h to 15.76 L·h. Work performance of the spray nozzle and heat transfer performance of the spray cooling system were analyzed; results show that this ejected spray cooling system has a good heat transfer performance and provides valid foundation for space closed-loop application in the near future.
基金supported by the National Natural Science Foundation of China (No. 11802238)。
文摘In this study,a neural adaptive controller is developed for a ground experiment with a spacecraft proximity operation.As the water resistance in the experiment is highly nonlinear and can significantly affect the fidelity of the ground experiment,the water resistance must be estimated accurately and compensated using an active force online.For this problem,a novel control algorithm combined with Chebyshev Neural Networks(CNN)and an Active Disturbance Rejection Control(ADRC)is proposed.Specifically,the CNN algorithm is used to estimate the water resistance.The advantage of the CNN estimation is that the coefficients of the approximation can be adaptively changed to minimize the estimation error.Combined with the ADRC algorithm,the total disturbance is compensated in the experiment to improve the fidelity.The dynamic model of the spacecraft proximity maneuver in the experiment is established.The ground experiment of the proximity maneuver that considers an obstacle is provided to verify the efficiency of the proposed controller.The results demonstrate that the proposed method outperforms the pure ADRC method and can achieve close-to-real-time performance for the spacecraft proximity maneuver.
