To eliminate anomalies and improve the performance of a space station remote manipulator(SSRM) used in a dynamically changeable thermal environment, we analyze the thermodynamic behavior of an SSRM that considers an i...To eliminate anomalies and improve the performance of a space station remote manipulator(SSRM) used in a dynamically changeable thermal environment, we analyze the thermodynamic behavior of an SSRM that considers an integrated thermal protection system(ITPS). Solar radiative heat gain and loss become equally significant as conductive heat transfers through the interior of the SSRM on orbit. A thermodynamic model of the SSRM with a sandwich ITPS structure is established on the coupling between harmonic drive and changeable thermal environment. A motion precision is proposed to evaluate thermodynamic behavior under continuously changeable thermal circumstances. Simulation results indicate that the ITPS with a corrugated sandwich structure reduces the maximum amplitude of angular position errors to 41.6%, which helps improve the motion precision of the SSRM. The feasible regions for the SSRM in the Low Earth Orbit(LEO) and Geostationary Earth Orbit(GEO) are analyzed, which shows that the proportion of feasible region in LEO is significantly larger than that in GEO.展开更多
High-precision detection of microwave field information is important in the fields of space wireless communication,space microwave remote sensing,and satellite navigation.In this paper,the high-precision detection of ...High-precision detection of microwave field information is important in the fields of space wireless communication,space microwave remote sensing,and satellite navigation.In this paper,the high-precision detection of broadband microwave is realized.High-precision detection of microwave fields has been realized for the first time based on the spin-mixing model of nitrogen-vacancy color centers and the continuous wave optically detected magnetic resonance(ODMR)process.By changing the power ratio between the signal and reference microwave fields,the validity of high-precision detection of microwaves is verified,and the microwave magnetic field detection resolution is less than 100 nW and the Pearson correlation coefficient of the system’s response to microwave intensity is 0.9974.Then,by optimizing the data acquisition time,the megahertz-level frequency resolution of the signal microwave is achieved.In addition,the gigahertz bandwidth and megahertz resolution were also verified by tuning the resonance frequency of the spin energy level to an external static magnetic field.These results provide an important technological basis for solid-state microwave receivers based on nitrogen-vacancy color centers,highprecision spectral resolution detection,and microwave sensing.展开更多
Given the limited ground infrastructure in remote areas such as suburbs and rural regions,Internet of Remote Things(IoRT)devices have been widely deployed to gather critical data and information.However,traditional da...Given the limited ground infrastructure in remote areas such as suburbs and rural regions,Internet of Remote Things(IoRT)devices have been widely deployed to gather critical data and information.However,traditional data transmission methods struggle to directly transmit the data to data processing centers.This paper proposes a space–air–ground Internet of Remote Things(SAG-IoRT)network architecture,which leverages the extensive coverage and efficient communication capabilities of satellites as its core advantage.In the SAG-IoRT network,low Earth orbit(LEO)satellites play a crucial role,addressing communication challenges in remote areas through their global coverage.Unmanned aerial vehicles(UAVs)serve as flexible bridges between ground and space,rapidly transmitting data collected by IoRT devices to LEO satellites,thereby enhancing data transmission efficiency and reliability.Our research focuses on optimizing the flight trajectories and scheduling strategies of UAVs to maximize the utilization of satellite communication resources,aiming to boost system throughput and reduce UAV energy consumption.To tackle the challenges of data collection and transmission in the dynamic and uncertain SAG-IoRT network environment,we formulate the optimization problem as a Markov decision process and apply the multi-agent deep deterministic policy gradient(MADDPG)algorithm to plan optimal paths for UAVs.Experimental results show that compared to the single-agent DDPG algorithm,the MADDPG-based solution not only improves system throughput by approximately 25.6%but also reduces UAV energy consumption by around 24.9%.This achievement underscores the pivotal role of satellites in advancing the development of IoRT and enabling efficient space-based communications.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.11272171)Education Ministry Doctoral Fund of China(Grant No.20120002110070)
文摘To eliminate anomalies and improve the performance of a space station remote manipulator(SSRM) used in a dynamically changeable thermal environment, we analyze the thermodynamic behavior of an SSRM that considers an integrated thermal protection system(ITPS). Solar radiative heat gain and loss become equally significant as conductive heat transfers through the interior of the SSRM on orbit. A thermodynamic model of the SSRM with a sandwich ITPS structure is established on the coupling between harmonic drive and changeable thermal environment. A motion precision is proposed to evaluate thermodynamic behavior under continuously changeable thermal circumstances. Simulation results indicate that the ITPS with a corrugated sandwich structure reduces the maximum amplitude of angular position errors to 41.6%, which helps improve the motion precision of the SSRM. The feasible regions for the SSRM in the Low Earth Orbit(LEO) and Geostationary Earth Orbit(GEO) are analyzed, which shows that the proportion of feasible region in LEO is significantly larger than that in GEO.
基金supported by the Joint Funds of the National Natural Science Foundation of China(U21A20141)the National Natural Science Foundation of China(52435011,62103385,62175219).
文摘High-precision detection of microwave field information is important in the fields of space wireless communication,space microwave remote sensing,and satellite navigation.In this paper,the high-precision detection of broadband microwave is realized.High-precision detection of microwave fields has been realized for the first time based on the spin-mixing model of nitrogen-vacancy color centers and the continuous wave optically detected magnetic resonance(ODMR)process.By changing the power ratio between the signal and reference microwave fields,the validity of high-precision detection of microwaves is verified,and the microwave magnetic field detection resolution is less than 100 nW and the Pearson correlation coefficient of the system’s response to microwave intensity is 0.9974.Then,by optimizing the data acquisition time,the megahertz-level frequency resolution of the signal microwave is achieved.In addition,the gigahertz bandwidth and megahertz resolution were also verified by tuning the resonance frequency of the spin energy level to an external static magnetic field.These results provide an important technological basis for solid-state microwave receivers based on nitrogen-vacancy color centers,highprecision spectral resolution detection,and microwave sensing.
基金supported in part by the National Key Research and Development Program of China under Grant No.2020YFB1807700。
文摘Given the limited ground infrastructure in remote areas such as suburbs and rural regions,Internet of Remote Things(IoRT)devices have been widely deployed to gather critical data and information.However,traditional data transmission methods struggle to directly transmit the data to data processing centers.This paper proposes a space–air–ground Internet of Remote Things(SAG-IoRT)network architecture,which leverages the extensive coverage and efficient communication capabilities of satellites as its core advantage.In the SAG-IoRT network,low Earth orbit(LEO)satellites play a crucial role,addressing communication challenges in remote areas through their global coverage.Unmanned aerial vehicles(UAVs)serve as flexible bridges between ground and space,rapidly transmitting data collected by IoRT devices to LEO satellites,thereby enhancing data transmission efficiency and reliability.Our research focuses on optimizing the flight trajectories and scheduling strategies of UAVs to maximize the utilization of satellite communication resources,aiming to boost system throughput and reduce UAV energy consumption.To tackle the challenges of data collection and transmission in the dynamic and uncertain SAG-IoRT network environment,we formulate the optimization problem as a Markov decision process and apply the multi-agent deep deterministic policy gradient(MADDPG)algorithm to plan optimal paths for UAVs.Experimental results show that compared to the single-agent DDPG algorithm,the MADDPG-based solution not only improves system throughput by approximately 25.6%but also reduces UAV energy consumption by around 24.9%.This achievement underscores the pivotal role of satellites in advancing the development of IoRT and enabling efficient space-based communications.
