The core module of China’s Space Station(CSS)is scheduled to be launched around the end of 2020,and the experimental module I and II will be launched in the next two years.After on-orbit constructions,CSS will be tra...The core module of China’s Space Station(CSS)is scheduled to be launched around the end of 2020,and the experimental module I and II will be launched in the next two years.After on-orbit constructions,CSS will be transferred into an operation period over 10 years(2022–2032 and beyond)to continuously implement space science missions.At present,based on the project selection and research work in the ground development period of CSS,China is systematically making a utilization mission planning for the operation period,which focuses on the fields of aerospace medicine and human research,space life science and biotechnology,microgravity fluid physics,combustion science,materials science,fundamental physics,space astronomy and astrophysics,Earth science,space physics and space environment,space application technology,etc.In combination with the latest development trend of space science and technology,China will continue to update planning for science research and technology development,carry out project cultivation,payload R&D,and upgrade onboard and ground experiment supporting systems to achieve greater comprehensive benefits in science,technology,economy,and society。展开更多
The rotational motion of a tumbling target brings great challenges to space robot on successfully capturing the tumbling target.Therefore,it is necessary to reduce the target's rotation to a rate at which capture ...The rotational motion of a tumbling target brings great challenges to space robot on successfully capturing the tumbling target.Therefore,it is necessary to reduce the target's rotation to a rate at which capture can be accomplished by the space robot.In this paper,a detumbling strategy based on friction control of dual-arm space robot for capturing tumbling target is proposed.This strategy can reduce the target's rotational velocity while maintaining base attitude stability through the establishment of the rotation attenuation controller and base attitude adjustment controller.The rotation attenuation controller adopts the multi-space hybrid impedance control method to control the friction precisely.The base attitude adjustment controller applies the dual-arm extended Jacobian matrix to stabilize the base attitude.The main contributions of this paper are as follows:(1)The compliant control method is adopted to achieve a precise friction control,which can reduce the target angular velocity steadily;(2)The dual-arm extended Jacobian matrix is applied to stabilize the base attitude without affecting the target capture task;(3)The detumbling strategy of dualarm space robot is designed considering base attitude stabilization,realizing coordinated planning of the base attitude and the arms.The strategy is verified by a dual-arm space robot with two 7-DOF(degrees of freedom)arms.Simulation results show that,target with a rotation velocity of 20(°)/s can be effectively controlled to stop within 30 s,and the final deflection of the base attitude is less than 0.15°without affecting the target capture task,verifying the correctness and effectiveness of the strategy.Except to the tumbling target capture task,the control strategy can also be applied to other typical on-orbit operation tasks such as space debris removal and spacecraft maintenance.展开更多
The reconstruction of spacecraft cluster based on local information and distributed strategy is investigated.Each spacecraft is an intelligent individual that can detect information within a limited range and can dete...The reconstruction of spacecraft cluster based on local information and distributed strategy is investigated.Each spacecraft is an intelligent individual that can detect information within a limited range and can determine its behavior based on surrounding information.The objective of the cluster is to achieve the formation reconstruction with minimum fuel consumption.Based on the principle of dual pulse rendezvous maneuver,three target selection strategies are designed for collision avoidance.Strategy-1 determines the target point’s attribution according to the target’s distance when the target point conflicts and uses a unit pulse to avoid a collision.Strategy-2 changes the collision avoidance behavior.When two spacecraft meet more than once,the strategy switches the target points of the two spacecraft.In Strategy-3,the spacecraft closer to the target has higher priority in target allocation.Strategy-3 also switches the target points when two spacecraft encounter more than once.The three strategies for a given position,different completion times,and random position are compared.Numerical simulations show that all three strategies can accomplish the spacecraft cluster's reconfiguration under the specified requirements.Strategy-3 is better than Strategy-1 in all simulation cases in the sense of less fuel consumption with different completion times and given location,and it is more effective than Strategy-2 in most of the completion time.With a random initial position and given time,Strategy-3 is better than Strategy-1 in about 70%of the cases and more stable.展开更多
This paper presents a new solution to haptic based teleoperation to control a large-sized slave robot for space exploration, which includes two specially designed haptic joysticks, a hybrid master-slave motion mapping...This paper presents a new solution to haptic based teleoperation to control a large-sized slave robot for space exploration, which includes two specially designed haptic joysticks, a hybrid master-slave motion mapping method, and a haptic feedback model rendering the operating resistance and the interactive feedback on the slave side. Two devices using the 3 R and DELTA mechanisms respectively are developed to be manipulated to control the position and orientation of a large-sized slave robot by using both of a user's two hands respectively. The hybrid motion mapping method combines rate control and variable scaled position mapping to realize accurate and efficient master-slave control. Haptic feedback for these two mapping modes is designed with emphasis on ergonomics to improve the immersion of haptic based teleoperation. A stiffness estimation method is used to calculate the contact stiffness on the slave side and play the contact force rendered by using a traditional spring-damping model to a user on the master side stably. Experiments by using virtual environments to simulate the slave side are conducted to validate the effectiveness and efficiency of the proposed solution.展开更多
This review article aims to give a comprehensive review of periodic orbits in the circular restricted three-body problem(CRTBP),which is a standard ideal model for the Earth-Moon system and is closest to the practical...This review article aims to give a comprehensive review of periodic orbits in the circular restricted three-body problem(CRTBP),which is a standard ideal model for the Earth-Moon system and is closest to the practical mechanical model.It focuses the attention on periodic orbits in the Earth-Moon system.This work is primarily motivated by a series of missions and plans that take advantages of the three-body periodic orbits near the libration points or around two gravitational celestial bodies.Firstly,simple periodic orbits and their classification that is usually considered to be early work before 1970 are summarized,and periodic orbits around Lagrange points,either planar or three-dimensional,are intensively studied during past decades.Subsequently,stability index of a periodic orbit and bifurcation analysis are presented,which demonstrate a guideline to find more periodic orbits inspired by bifurcation signals.Then,the practical techniques for computing a wide range of periodic orbits and associated quasi-periodic orbits,as well as constructing database of periodic orbits by numerical searching techniques are also presented.For those unstable periodic orbits,the station keeping maneuvers are reviewed.Finally,the applications of periodic orbits are presented,including those in practical missions,under consideration,and still in conceptual design stage.This review article has the function of bridging between engineers and researchers,so as to make it more convenient and faster for engineers to understand the complex restricted three-body problem(RTBP).At the same time,it can also provide some technical thinking for general researchers.展开更多
In the 6th edition of the Chinese Space Trajectory Design Competition held in 2014, a near-Earth asteroid sample-return trajectory design problem was released, in which the motion of the spacecraft is modeled in multi...In the 6th edition of the Chinese Space Trajectory Design Competition held in 2014, a near-Earth asteroid sample-return trajectory design problem was released, in which the motion of the spacecraft is modeled in multi-body dynamics, considering the gravitational forces of the Sun, Earth, and Moon. It is proposed that an electric-propulsion spacecraft initially parking in a circular 200-kin-altitude low Earth orbit is expected to rendezvous with an asteroid and carry as much sample as possible back to the Earth in a 10-year time frame. The team from the Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences has reported a solution with an asteroid sample mass of 328 tons, which is ranked first in the competition. In this article, we will present our design and optimization methods, primarily including overall analysis, target selection, escape from and capture by the Earth-Moon system, and optimization of impulsive and low-thrust trajectories that are modeled in multi-body dynamics. The orbital resonance concept and lunar gravity assists are considered key techniques employed for trajectory design. The reported solution, preliminarily revealing the feasibility of returning a hundreds-of-tons asteroid or asteroid sample, envisions future space missions relating to near-Earth asteroid exploration.展开更多
Space swarms,enabled by the miniaturization of spacecraft,have the potential capability to lower costs,increase efficiencies,and broaden the horizons of space missions.The formation control problem of large-scale spac...Space swarms,enabled by the miniaturization of spacecraft,have the potential capability to lower costs,increase efficiencies,and broaden the horizons of space missions.The formation control problem of large-scale spacecraft swarms flying around an elliptic orbit is considered.The objective is to drive the entire formation to produce a specified spatial pattern.The relative motion between agents becomes complicated as the number of agents increases.Hence,a density-based method is adopted,which concerns the density evolution of the entire swarm instead of the trajectories of individuals.The density-based method manipulates the density evolution with Partial Differential Equations(PDEs).This density-based control in this work has two aspects,global pattern control of the whole swarm and local collision-avoidance between nearby agents.The global behavior of the swarm is driven via designing velocity fields.For each spacecraft,the Q-guidance steering law is adopted to track the desired velocity with accelerations in a distributed manner.However,the final stable velocity field is required to be zero in the classical density-based approach,which appears as an obstacle from the viewpoint of astrodynamics since the periodic relative motion is always time-varying.To solve this issue,a novel transformation is constructed based on the periodic solutions of Tschauner-Hempel(TH)equations.The relative motion in Cartesian coordinates is then transformed into a new coordinate system,which permits zero-velocity in a stable configuration.The local behavior of the swarm,such as achieving collision avoidance,is achieved via a carefully-designed local density estimation algorithm.Numerical simulations are provided to demonstrate the performance of this approach.展开更多
Chinese Space Station(CSS)has been fully deployed by the end of 2022,and the facility has entered into the application and development phase.It has conducted scientific research projects in various fields,such as spac...Chinese Space Station(CSS)has been fully deployed by the end of 2022,and the facility has entered into the application and development phase.It has conducted scientific research projects in various fields,such as space life science and biotechnology,space materials science,microgravity fundamental physics,fluid physics,combustion science,space new technologies,and applications.In this review,we introduce the progress of CSS development and provide an overview of the research conducted in Chinese Space Station and the recent scientific findings in several typical research fields.Such compelling findings mainly concern the rapid solidification of ultra-high temperature alloy melts,dynamics of fluid transport in space,gravity scaling law of boiling heat transfer,vibration fluidization phenomenon of particulate matter,cold atom interferometer technology under high microgravity and related equivalence principle testing,the full life cycle of rice under microgravity and so forth.Furthermore,the planned scientific research and corresponding prospects of Chinese space station in the next few years are presented.展开更多
An improved wave-plate demister equipped with vortex generators(VGs)has been proposed for wet flue gas desulfurization systems(WFGD)in this work.Numerical and experimental methods were used to evaluate the effect of V...An improved wave-plate demister equipped with vortex generators(VGs)has been proposed for wet flue gas desulfurization systems(WFGD)in this work.Numerical and experimental methods were used to evaluate the effect of VGs on the separation of small droplets.Five types of wave-plate demister with different VGs were analyzed.The vortex generators in question included rectangular plates,semi-elliptical plates,square tubes,round tubes,and triangular tubes,respectively.In order to explain the strengthening mechanism,the distribution of flow field,secondary flow,and droplet trajectory were shown,and the effect of VGs on the flow field in the demister was discussed in depth.The simulation results show that the separation performances of the demisters with VGs were significantly improved over that of the initial demister,and the accompanying pressure drop was small.For the vortex generators studied,the rectangular plate fully demonstrated its superior separation performance,followed by semi-elliptical plate.The strengthening effect of VGs was tested through experiments.Experimental data reveal that the average droplet diameter(D_(50))at the outlet of the demister with a vortex generator can be reduced to 23.13μm,whereas this value for the initial demister can be maintained at 32.07μm.Moreover,compared with the original demister 0.81,the overall separation efficiency of the improved demister was improved to 0.92.展开更多
High-specific-impulse electric propulsion technology is promising for future space robotic debris removal in sun-synchronous orbits.Such a prospect involves solving a class of challenging problems of low-thrust orbita...High-specific-impulse electric propulsion technology is promising for future space robotic debris removal in sun-synchronous orbits.Such a prospect involves solving a class of challenging problems of low-thrust orbital rendezvous between an active spacecraft and a free-flying debris.This study focuses on computing optimal low-thrust minimum-time many-revolution trajectories,considering the effects of the Earth oblateness perturbations and null thrust in Earth shadow.Firstly,a set of mean-element orbital dynamic equations of a chaser(spacecraft)and a target(debris)are derived by using the orbital averaging technique,and specifically a slow-changing state of the mean longitude difference is proposed to accommodate to the rendezvous problem.Subsequently,the corresponding optimal control problem is formulated based on the mean elements and their associated costate variables in terms of Pontryagin’s maximum principle,and a practical optimization procedure is adopted to find the specific initial costate variables,wherein the necessary conditions of the optimal solutions are all satisfied.Afterwards,the optimal control profile obtained in mean elements is then mapped into the counterpart that is employed by the osculating orbital dynamics.A simple correction strategy about the initialization of the mean elements,specifically the differential mean true longitude,is suggested,which is capable of minimizing the terminal orbital rendezvous errors for propagating orbital dynamics expressed by both mean and osculating elements.Finally,numerical examples are presented,and specifically,the terminal orbital rendezvous accuracy is verified by solving hundreds of rendezvous problems,demonstrating the effectiveness of the optimization method proposed in this article.展开更多
Surface cracks are commonly observed in coatings and films.When structures with coatings are subject to stretching,opening mode cracks are likely to form on the surface,which may further lead to other forms of damage,...Surface cracks are commonly observed in coatings and films.When structures with coatings are subject to stretching,opening mode cracks are likely to form on the surface,which may further lead to other forms of damage,such as interfacial delamination and substrate damage.Possible crack forms include cracks extending towards the interface and channeling across the film.In this paper,a two-dimensional numerical model is proposed to obtain the structural strain energy at arbitrary crack lengths for bilayer structures under uniaxial tension.The energy release rate and structural stress intensity factors can be obtained accordingly,and the effects of geometry and material features on fracture characteristics are investigated,with most crack patterns being confirmed as unstable.The proposed model can also facilitate the analysis of the stress distribution in periodic crack patterns of films.The results from the numerical model are compared with those obtained by the finite element method(FEM),and the accuracy of the theoretical results is demonstrated.展开更多
The capture operation performed by a snare-type end-effector mainly relies on three flexible cables.This paper solves the dynamics modeling problems of flexible cable used in the snare-type end-effector and provides a...The capture operation performed by a snare-type end-effector mainly relies on three flexible cables.This paper solves the dynamics modeling problems of flexible cable used in the snare-type end-effector and provides a contact tracking control strategy for the impact phase of snare capture.To describe the motion of flexible cable,a dynamics model is established by considering both tensile and bending resistance properties.On this basis,a virtual spring concept is introduced to represent the contact between flexible cables and the target grapple shaft,and a contact dynamics model is established approximately by polynomial function with the variables of penetration and start-end distance of flexible cable.Thereafter,a contact tracking control strategy is proposed to improve the reliability of space snare capture.The target grapple shaft and flexible cable can keep in contact at the initial contact point during the whole capture process and thus reduce the possibility of pushing the target away.Experiments are carried out to verify the effectiveness of the proposed method.展开更多
Distant Retrograde Orbits(DROs)in the Earth-Moon system have great potential to support varieties of missions due to the favorable stability and orbital positions.Thus,the close relative motion on DROs should be analy...Distant Retrograde Orbits(DROs)in the Earth-Moon system have great potential to support varieties of missions due to the favorable stability and orbital positions.Thus,the close relative motion on DROs should be analyzed to design formations to assist or extend the DRO missions.However,as the reference DROs are obtained through numerical methods,the close relative motions on DROs are non-analytical,which severely limits the design of relative trajectories.In this paper,a novel approach is proposed to construct the analytical solution of bounded close relative motion on DROs.The linear dynamics of relative motion on DRO is established at first.The preliminary forms of the general solutions are obtained based on the Floquet theory.And the general solutions are classified as different modes depending on their periodic components.A new parameterization is applied to each mode,which allows us to explore the geometries of quasi-periodic modes in detail.In each mode,the solutions are integrated as a uniform expression and their periodic components are expanded as truncated Fourier series.In this way,the analytical bounded relative motion on DRO is obtained.Based on the analytical expression,the characteristics of different modes are comprehensively analyzed.The natural periodic mode is always located on the single side of the target spacecraft on DRO and is appropriate to be the parking orbits of the rendezvous and docking.On the basis of quasi-periodic modes,quasi-elliptical fly-around relative trajectories are designed with the assistance of only two impulses per period.The fly-around formation can support observations to targets on DRO from multiple viewing angles.And the fly-around formation is validated in a more practical ephemeris model.展开更多
The knowledge of crack type and dislocation orientation is helpful for the lifetime prediction of thin plates on aircrafts.The moment-tensor inversion utilizes the Acoustic Emission(AE)signals to detect cracks and the...The knowledge of crack type and dislocation orientation is helpful for the lifetime prediction of thin plates on aircrafts.The moment-tensor inversion utilizes the Acoustic Emission(AE)signals to detect cracks and the source mechanisms can be interpreted by the decomposition of moment tensors.Since the traditional moment-tensor inversion is implemented for the AE sources inside infinite elastic bodies,the inversion needs to be modified for the cracks in thin plates.In this study,the moment tensors of cracks in thin plates are derived and the inversion equation is provided based on the Green's function of second kind.A method of modifying the moment tensors to adapt to the existing decomposition processes and source-type plots is provided.By employing the Finite Element Method(FEM),the wave fields generated by the AE sources are computed.The AE sources continuously changing from pure tensile type(Model I)to shear type(Model II)are achieved in the FE models and the moment tensors are recovered.By the comparison between the reference values and recovered solutions,the source type can be accurately identified in the source-type plot and the applicability of the moment-tensor inversion for cracks in thin plates is confirmed.展开更多
The high-speed movement of satellites makes it not feasible to directly apply the mature routing scheme on the ground to the satellite network.DT-DVTR in the snapshot-based connectionoriented routing strategy is one o...The high-speed movement of satellites makes it not feasible to directly apply the mature routing scheme on the ground to the satellite network.DT-DVTR in the snapshot-based connectionoriented routing strategy is one of the representative solutions,but it still has room for improvement in terms of routing stability.In this paper,we propose an improved scheme for connection-oriented routing strategy named the Minimal Topology Change Routing based on Collaborative Rules(MTCR-CR).The MTCR-CR uses continuous time static topology snapshots based on satellite status to search for intersatellite link(ISL)construction solutions that meet the minimum number of topology changes to avoid route oscillations.The simulation results in Beidou-3 show that compared with DT-DVTR,MTCR-CR reduces the number of routing changes by about 92%,the number of path changes caused by routing changes is about38%,and the rerouting time is reduced by approximately 47%.At the same time,in order to show our algorithm more comprehensively,the same experimental index test was also carried out on the Globalstar satellite constellation.展开更多
The 2:1 resonant distant retrograde orbit(DRO),known for its long-term stability and global accessibility,holds strategic significance in current Earth-Moon space mission explorations.This paper conducts a comprehensi...The 2:1 resonant distant retrograde orbit(DRO),known for its long-term stability and global accessibility,holds strategic significance in current Earth-Moon space mission explorations.This paper conducts a comprehensive analysis of the problem of low-energy transferring into 2:1 DRO using the weak stability boundary(WSB)and lunar gravity assist(LGA)in the planar bi-circular restricted four-body problem(BCR4BP).The transfer process is categorized into three phases:the Earth-Moon transfer,Sun-Earth weak stability boundary transfer,and DRO low-energy capture.Addressing key questions,our study investigates:(1)Under what LGA conditions can the spacecraft reach the approximate area where the WSB region is situated?(2)How do trajectories,upon reaching the region where the WSB is located,return to the vicinity of 2:1 DRO,potentially facilitating low-energy DRO insertion?Our study involved a comprehensive analysis of the spacecraft’s changes in Earth-Moon mechanical energy and Jacobi energy during the entire transfer process.This analysis yielded the energy and geometric conditions necessary for potential low-energy DRO insertion,effectively filtering out numerous impractical candidate trajectories and enhancing computational effciency.In this paper,the geometric condition is referred to as the low-energy transfer gateway(LETG).Using the LEGT as the stitching interface,a significant number of feasible solutions were obtained effectively for bi-impulse DRO transfer trajectories through differential correction,some of which were previously undiscovered.展开更多
The 12th Global Trajectory Optimization Competition challenged teams to design trajectories for mining asteroids and transporting extracted resources back to the Earth. This paper outlines the methods and results of t...The 12th Global Trajectory Optimization Competition challenged teams to design trajectories for mining asteroids and transporting extracted resources back to the Earth. This paper outlines the methods and results of the runner-up team, BIT-CAS-DFH, highlighting an overall analysis of the approach as well as detailed descriptions of the methods used. The approach begins with building databases to reduce computational costs in trajectory design. Then, asteroid sequences are determined. A segmentation-based approach was adopted to efficiently handle the large dataset. Each sequence was divided into four time-based segments. Segments 1 and 4 were generated forward and backward, respectively, using a breadth-first beam search. Candidates for these segments were refined using genetic and greedy algorithms. Segments 2 and 3 were then generated and selected forward and backward based on the results of Segments 1 and 4. Following this, a matching process paired candidates from Segments 2 and 3. With the asteroid sequences established, low-thrust trajectories were optimized using indirect methods. A local optimization strategy was employed to maximize the collected mass by fine-tuning rendezvous timings. The final solution is presented, with comparative analyses against other teams’ approaches.展开更多
The Microgravity Active vibration Isolation System(MAIS),which was onboard China’s first cargo-spacecraft Tianzhou-1 launched on April 20,2017,aims to provide high-level microgravity at an order of 10^(-5)–10^(-6)g ...The Microgravity Active vibration Isolation System(MAIS),which was onboard China’s first cargo-spacecraft Tianzhou-1 launched on April 20,2017,aims to provide high-level microgravity at an order of 10^(-5)–10^(-6)g for specific scientific experiments.MAIS is mainly composed of a stator and a floater,and payloads are mounted on the floater.Sensing relative motion with respect to the stator fixed on the spacecraft,the floater is isolated from vibration on the stator via control forces and torques generated by electromagnetic actuators.This isolation results in a high-level microgravity environment.Before MAIS was launched into space,its control performance had been simulated on computers and tested by air-bearing platform levitation and aircraft parabolic flight.This article first presents an overview of the MAIS’s hardware system,particularly system structure,measurement sensors,and control actuators.Its system dynamics,state estimation,and control laws are then discussed,followed by the results of computer simulation and engineering tests,including the test of the six-degree-of-freedom motion by aircraft parabolic flight.Simulation and test results verify the accuracy of the control strategy design,effectiveness of the control algorithms,and performance of the entire control system,paving the way for operation of MAIS in space.This article also presents the steps recommended for the control performance simulation and tests of MAIS-like devices.These devices are expected to be used on China’s Space Station for various scientific experiments that require a high-level microgravity environment.展开更多
In our Lett er, we selec ted several commercial optical t ransceivers, which consist of single-channel transceiver modules, parallel transmitting and receiving modules, and Ethernet passive optical network (EPON) opti...In our Lett er, we selec ted several commercial optical t ransceivers, which consist of single-channel transceiver modules, parallel transmitting and receiving modules, and Ethernet passive optical network (EPON) optical linet erminal (OLT) and optical net work unit (ONU) modules, to do the total ionizing dose (TID) testing via the gamma-ray radiation method. The changing of current and receiver sensitivity of optical transceivers is discussed and analyzed. Based on the TID testing exposed to a TID of 50 krad (Si) at a dose rate of about 0.1 rad (Si)/s, the performance of single-channel transceivers and parallel receiving modules has not changed after 50 krad (Si) exposure, the parallel transmitting and EPON ONU modules have not worked after 40 krad (Si) and 47 krad (Si) exposure, the EPON OLT module has bit error in the process of irradiation, and it can work well after annealing;the reason for the error of OLT is analyzed. Finally, based on the theoretical analysis and testing results, this Letter provides several design suggestions to improve the reliability for optical transceivers, which can be referenced by satellite system designation for various space missions.展开更多
This study aims to assess the autonomous navigation performance of an asteroid orbiter enhanced using an inter-satellite link to a beacon satellite.Autonomous navigation includes the orbit determination of the orbiter...This study aims to assess the autonomous navigation performance of an asteroid orbiter enhanced using an inter-satellite link to a beacon satellite.Autonomous navigation includes the orbit determination of the orbiter and beacon,and asteroid gravity estimation without any ground station support.Navigation measurements were acquired using satellite-to-satellite tracking(SST)and optical observation of asteroid surface landmarks.This study presents a new orbiter-beacon SST scheme,in which the orbiter circumnavigates the asteroid in a low-altitude strongly-perturbed orbit,and the beacon remains in a high-altitude weakly-perturbed orbit.We used Asteroid 433 Eros as an example,and analyzed and designed low-and high-altitude orbits for the orbiter and beacon.The navigation measurements were precisely modeled,extended Kalman filters were devised,and observation configuration was analyzed using the Cramer-Rao lower bound(CRLB).Monte Carlo simulations were carried out to assess the effects of the orbital inclination and altitudes of the orbiter and beacon as key influencing factors.The simulation results showed that the proposed SST scheme was an effective solution for enhancing the autonomous navigation performance of the orbiter,particularly for improving the accuracy of gravity estimation.展开更多
文摘The core module of China’s Space Station(CSS)is scheduled to be launched around the end of 2020,and the experimental module I and II will be launched in the next two years.After on-orbit constructions,CSS will be transferred into an operation period over 10 years(2022–2032 and beyond)to continuously implement space science missions.At present,based on the project selection and research work in the ground development period of CSS,China is systematically making a utilization mission planning for the operation period,which focuses on the fields of aerospace medicine and human research,space life science and biotechnology,microgravity fluid physics,combustion science,materials science,fundamental physics,space astronomy and astrophysics,Earth science,space physics and space environment,space application technology,etc.In combination with the latest development trend of space science and technology,China will continue to update planning for science research and technology development,carry out project cultivation,payload R&D,and upgrade onboard and ground experiment supporting systems to achieve greater comprehensive benefits in science,technology,economy,and society。
基金co-supported by the National Natural Science Foundation of China(Nos.61403038 and 61573066)the Open Research Fund of Key Laboratory of Space Utilization,Chinese Academy of Sciences(Nos.LSU-2016-05-2 and LSUKJTS-2017-02)。
文摘The rotational motion of a tumbling target brings great challenges to space robot on successfully capturing the tumbling target.Therefore,it is necessary to reduce the target's rotation to a rate at which capture can be accomplished by the space robot.In this paper,a detumbling strategy based on friction control of dual-arm space robot for capturing tumbling target is proposed.This strategy can reduce the target's rotational velocity while maintaining base attitude stability through the establishment of the rotation attenuation controller and base attitude adjustment controller.The rotation attenuation controller adopts the multi-space hybrid impedance control method to control the friction precisely.The base attitude adjustment controller applies the dual-arm extended Jacobian matrix to stabilize the base attitude.The main contributions of this paper are as follows:(1)The compliant control method is adopted to achieve a precise friction control,which can reduce the target angular velocity steadily;(2)The dual-arm extended Jacobian matrix is applied to stabilize the base attitude without affecting the target capture task;(3)The detumbling strategy of dualarm space robot is designed considering base attitude stabilization,realizing coordinated planning of the base attitude and the arms.The strategy is verified by a dual-arm space robot with two 7-DOF(degrees of freedom)arms.Simulation results show that,target with a rotation velocity of 20(°)/s can be effectively controlled to stop within 30 s,and the final deflection of the base attitude is less than 0.15°without affecting the target capture task,verifying the correctness and effectiveness of the strategy.Except to the tumbling target capture task,the control strategy can also be applied to other typical on-orbit operation tasks such as space debris removal and spacecraft maintenance.
基金supported by the Advanced Research Project of China Manned Space Program.
文摘The reconstruction of spacecraft cluster based on local information and distributed strategy is investigated.Each spacecraft is an intelligent individual that can detect information within a limited range and can determine its behavior based on surrounding information.The objective of the cluster is to achieve the formation reconstruction with minimum fuel consumption.Based on the principle of dual pulse rendezvous maneuver,three target selection strategies are designed for collision avoidance.Strategy-1 determines the target point’s attribution according to the target’s distance when the target point conflicts and uses a unit pulse to avoid a collision.Strategy-2 changes the collision avoidance behavior.When two spacecraft meet more than once,the strategy switches the target points of the two spacecraft.In Strategy-3,the spacecraft closer to the target has higher priority in target allocation.Strategy-3 also switches the target points when two spacecraft encounter more than once.The three strategies for a given position,different completion times,and random position are compared.Numerical simulations show that all three strategies can accomplish the spacecraft cluster's reconfiguration under the specified requirements.Strategy-3 is better than Strategy-1 in all simulation cases in the sense of less fuel consumption with different completion times and given location,and it is more effective than Strategy-2 in most of the completion time.With a random initial position and given time,Strategy-3 is better than Strategy-1 in about 70%of the cases and more stable.
基金supported by the Open Research Fund of Key Laboratory of Space Utilization,Chinese Academy of Sciences(No.LSU-YKZX-2017-02)
文摘This paper presents a new solution to haptic based teleoperation to control a large-sized slave robot for space exploration, which includes two specially designed haptic joysticks, a hybrid master-slave motion mapping method, and a haptic feedback model rendering the operating resistance and the interactive feedback on the slave side. Two devices using the 3 R and DELTA mechanisms respectively are developed to be manipulated to control the position and orientation of a large-sized slave robot by using both of a user's two hands respectively. The hybrid motion mapping method combines rate control and variable scaled position mapping to realize accurate and efficient master-slave control. Haptic feedback for these two mapping modes is designed with emphasis on ergonomics to improve the immersion of haptic based teleoperation. A stiffness estimation method is used to calculate the contact stiffness on the slave side and play the contact force rendered by using a traditional spring-damping model to a user on the master side stably. Experiments by using virtual environments to simulate the slave side are conducted to validate the effectiveness and efficiency of the proposed solution.
文摘This review article aims to give a comprehensive review of periodic orbits in the circular restricted three-body problem(CRTBP),which is a standard ideal model for the Earth-Moon system and is closest to the practical mechanical model.It focuses the attention on periodic orbits in the Earth-Moon system.This work is primarily motivated by a series of missions and plans that take advantages of the three-body periodic orbits near the libration points or around two gravitational celestial bodies.Firstly,simple periodic orbits and their classification that is usually considered to be early work before 1970 are summarized,and periodic orbits around Lagrange points,either planar or three-dimensional,are intensively studied during past decades.Subsequently,stability index of a periodic orbit and bifurcation analysis are presented,which demonstrate a guideline to find more periodic orbits inspired by bifurcation signals.Then,the practical techniques for computing a wide range of periodic orbits and associated quasi-periodic orbits,as well as constructing database of periodic orbits by numerical searching techniques are also presented.For those unstable periodic orbits,the station keeping maneuvers are reviewed.Finally,the applications of periodic orbits are presented,including those in practical missions,under consideration,and still in conceptual design stage.This review article has the function of bridging between engineers and researchers,so as to make it more convenient and faster for engineers to understand the complex restricted three-body problem(RTBP).At the same time,it can also provide some technical thinking for general researchers.
基金supported by the National Natural Science Foundation of China(Grant11372311)the grant from the State key Laboratory of Astronautic Dynamics(2014-ADL-DW0201)
文摘In the 6th edition of the Chinese Space Trajectory Design Competition held in 2014, a near-Earth asteroid sample-return trajectory design problem was released, in which the motion of the spacecraft is modeled in multi-body dynamics, considering the gravitational forces of the Sun, Earth, and Moon. It is proposed that an electric-propulsion spacecraft initially parking in a circular 200-kin-altitude low Earth orbit is expected to rendezvous with an asteroid and carry as much sample as possible back to the Earth in a 10-year time frame. The team from the Technology and Engineering Center for Space Utilization, Chinese Academy of Sciences has reported a solution with an asteroid sample mass of 328 tons, which is ranked first in the competition. In this article, we will present our design and optimization methods, primarily including overall analysis, target selection, escape from and capture by the Earth-Moon system, and optimization of impulsive and low-thrust trajectories that are modeled in multi-body dynamics. The orbital resonance concept and lunar gravity assists are considered key techniques employed for trajectory design. The reported solution, preliminarily revealing the feasibility of returning a hundreds-of-tons asteroid or asteroid sample, envisions future space missions relating to near-Earth asteroid exploration.
基金co-supported by the Strategic Priority Program on Space Science of the Chinese Academy of Sciences (No.XDA15014902)the Key Research Program of the Chinese Academy of Sciences (No. ZDRW-KT-2019-1-0102)
文摘Space swarms,enabled by the miniaturization of spacecraft,have the potential capability to lower costs,increase efficiencies,and broaden the horizons of space missions.The formation control problem of large-scale spacecraft swarms flying around an elliptic orbit is considered.The objective is to drive the entire formation to produce a specified spatial pattern.The relative motion between agents becomes complicated as the number of agents increases.Hence,a density-based method is adopted,which concerns the density evolution of the entire swarm instead of the trajectories of individuals.The density-based method manipulates the density evolution with Partial Differential Equations(PDEs).This density-based control in this work has two aspects,global pattern control of the whole swarm and local collision-avoidance between nearby agents.The global behavior of the swarm is driven via designing velocity fields.For each spacecraft,the Q-guidance steering law is adopted to track the desired velocity with accelerations in a distributed manner.However,the final stable velocity field is required to be zero in the classical density-based approach,which appears as an obstacle from the viewpoint of astrodynamics since the periodic relative motion is always time-varying.To solve this issue,a novel transformation is constructed based on the periodic solutions of Tschauner-Hempel(TH)equations.The relative motion in Cartesian coordinates is then transformed into a new coordinate system,which permits zero-velocity in a stable configuration.The local behavior of the swarm,such as achieving collision avoidance,is achieved via a carefully-designed local density estimation algorithm.Numerical simulations are provided to demonstrate the performance of this approach.
文摘Chinese Space Station(CSS)has been fully deployed by the end of 2022,and the facility has entered into the application and development phase.It has conducted scientific research projects in various fields,such as space life science and biotechnology,space materials science,microgravity fundamental physics,fluid physics,combustion science,space new technologies,and applications.In this review,we introduce the progress of CSS development and provide an overview of the research conducted in Chinese Space Station and the recent scientific findings in several typical research fields.Such compelling findings mainly concern the rapid solidification of ultra-high temperature alloy melts,dynamics of fluid transport in space,gravity scaling law of boiling heat transfer,vibration fluidization phenomenon of particulate matter,cold atom interferometer technology under high microgravity and related equivalence principle testing,the full life cycle of rice under microgravity and so forth.Furthermore,the planned scientific research and corresponding prospects of Chinese space station in the next few years are presented.
基金This work was supported by the Foundation of key Laboratory of Space Utilization,Technology and Engineering Center for Space Utilization,Chinese Academy of Sciences(CSU-QZKT-2018-09)Open Project of Beijing Key Laboratory of Measurement and Control of Mechanical and Electrical System under Grant No.KF20181123205.
文摘An improved wave-plate demister equipped with vortex generators(VGs)has been proposed for wet flue gas desulfurization systems(WFGD)in this work.Numerical and experimental methods were used to evaluate the effect of VGs on the separation of small droplets.Five types of wave-plate demister with different VGs were analyzed.The vortex generators in question included rectangular plates,semi-elliptical plates,square tubes,round tubes,and triangular tubes,respectively.In order to explain the strengthening mechanism,the distribution of flow field,secondary flow,and droplet trajectory were shown,and the effect of VGs on the flow field in the demister was discussed in depth.The simulation results show that the separation performances of the demisters with VGs were significantly improved over that of the initial demister,and the accompanying pressure drop was small.For the vortex generators studied,the rectangular plate fully demonstrated its superior separation performance,followed by semi-elliptical plate.The strengthening effect of VGs was tested through experiments.Experimental data reveal that the average droplet diameter(D_(50))at the outlet of the demister with a vortex generator can be reduced to 23.13μm,whereas this value for the initial demister can be maintained at 32.07μm.Moreover,compared with the original demister 0.81,the overall separation efficiency of the improved demister was improved to 0.92.
基金supported by the National Key Research and Development Project(Grant No.2018YFB1900605)the Key Research Program of Chinese Academy of Sciences(Grant No.ZDRW-KT-2019-1).
文摘High-specific-impulse electric propulsion technology is promising for future space robotic debris removal in sun-synchronous orbits.Such a prospect involves solving a class of challenging problems of low-thrust orbital rendezvous between an active spacecraft and a free-flying debris.This study focuses on computing optimal low-thrust minimum-time many-revolution trajectories,considering the effects of the Earth oblateness perturbations and null thrust in Earth shadow.Firstly,a set of mean-element orbital dynamic equations of a chaser(spacecraft)and a target(debris)are derived by using the orbital averaging technique,and specifically a slow-changing state of the mean longitude difference is proposed to accommodate to the rendezvous problem.Subsequently,the corresponding optimal control problem is formulated based on the mean elements and their associated costate variables in terms of Pontryagin’s maximum principle,and a practical optimization procedure is adopted to find the specific initial costate variables,wherein the necessary conditions of the optimal solutions are all satisfied.Afterwards,the optimal control profile obtained in mean elements is then mapped into the counterpart that is employed by the osculating orbital dynamics.A simple correction strategy about the initialization of the mean elements,specifically the differential mean true longitude,is suggested,which is capable of minimizing the terminal orbital rendezvous errors for propagating orbital dynamics expressed by both mean and osculating elements.Finally,numerical examples are presented,and specifically,the terminal orbital rendezvous accuracy is verified by solving hundreds of rendezvous problems,demonstrating the effectiveness of the optimization method proposed in this article.
基金Project supported by the National Natural Science Foundation of China(Nos.12172027 and 11572022)。
文摘Surface cracks are commonly observed in coatings and films.When structures with coatings are subject to stretching,opening mode cracks are likely to form on the surface,which may further lead to other forms of damage,such as interfacial delamination and substrate damage.Possible crack forms include cracks extending towards the interface and channeling across the film.In this paper,a two-dimensional numerical model is proposed to obtain the structural strain energy at arbitrary crack lengths for bilayer structures under uniaxial tension.The energy release rate and structural stress intensity factors can be obtained accordingly,and the effects of geometry and material features on fracture characteristics are investigated,with most crack patterns being confirmed as unstable.The proposed model can also facilitate the analysis of the stress distribution in periodic crack patterns of films.The results from the numerical model are compared with those obtained by the finite element method(FEM),and the accuracy of the theoretical results is demonstrated.
基金supported by the National Natural Science Foundation of China (Nos.11672294, 61903354)
文摘The capture operation performed by a snare-type end-effector mainly relies on three flexible cables.This paper solves the dynamics modeling problems of flexible cable used in the snare-type end-effector and provides a contact tracking control strategy for the impact phase of snare capture.To describe the motion of flexible cable,a dynamics model is established by considering both tensile and bending resistance properties.On this basis,a virtual spring concept is introduced to represent the contact between flexible cables and the target grapple shaft,and a contact dynamics model is established approximately by polynomial function with the variables of penetration and start-end distance of flexible cable.Thereafter,a contact tracking control strategy is proposed to improve the reliability of space snare capture.The target grapple shaft and flexible cable can keep in contact at the initial contact point during the whole capture process and thus reduce the possibility of pushing the target away.Experiments are carried out to verify the effectiveness of the proposed method.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA30010200)。
文摘Distant Retrograde Orbits(DROs)in the Earth-Moon system have great potential to support varieties of missions due to the favorable stability and orbital positions.Thus,the close relative motion on DROs should be analyzed to design formations to assist or extend the DRO missions.However,as the reference DROs are obtained through numerical methods,the close relative motions on DROs are non-analytical,which severely limits the design of relative trajectories.In this paper,a novel approach is proposed to construct the analytical solution of bounded close relative motion on DROs.The linear dynamics of relative motion on DRO is established at first.The preliminary forms of the general solutions are obtained based on the Floquet theory.And the general solutions are classified as different modes depending on their periodic components.A new parameterization is applied to each mode,which allows us to explore the geometries of quasi-periodic modes in detail.In each mode,the solutions are integrated as a uniform expression and their periodic components are expanded as truncated Fourier series.In this way,the analytical bounded relative motion on DRO is obtained.Based on the analytical expression,the characteristics of different modes are comprehensively analyzed.The natural periodic mode is always located on the single side of the target spacecraft on DRO and is appropriate to be the parking orbits of the rendezvous and docking.On the basis of quasi-periodic modes,quasi-elliptical fly-around relative trajectories are designed with the assistance of only two impulses per period.The fly-around formation can support observations to targets on DRO from multiple viewing angles.And the fly-around formation is validated in a more practical ephemeris model.
基金financial supports provided by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22000000)National Natural Science Foundation of China(No.41804134)。
文摘The knowledge of crack type and dislocation orientation is helpful for the lifetime prediction of thin plates on aircrafts.The moment-tensor inversion utilizes the Acoustic Emission(AE)signals to detect cracks and the source mechanisms can be interpreted by the decomposition of moment tensors.Since the traditional moment-tensor inversion is implemented for the AE sources inside infinite elastic bodies,the inversion needs to be modified for the cracks in thin plates.In this study,the moment tensors of cracks in thin plates are derived and the inversion equation is provided based on the Green's function of second kind.A method of modifying the moment tensors to adapt to the existing decomposition processes and source-type plots is provided.By employing the Finite Element Method(FEM),the wave fields generated by the AE sources are computed.The AE sources continuously changing from pure tensile type(Model I)to shear type(Model II)are achieved in the FE models and the moment tensors are recovered.By the comparison between the reference values and recovered solutions,the source type can be accurately identified in the source-type plot and the applicability of the moment-tensor inversion for cracks in thin plates is confirmed.
基金supported by the National Key Research and Development Program of China(No.2020YFB1806000)。
文摘The high-speed movement of satellites makes it not feasible to directly apply the mature routing scheme on the ground to the satellite network.DT-DVTR in the snapshot-based connectionoriented routing strategy is one of the representative solutions,but it still has room for improvement in terms of routing stability.In this paper,we propose an improved scheme for connection-oriented routing strategy named the Minimal Topology Change Routing based on Collaborative Rules(MTCR-CR).The MTCR-CR uses continuous time static topology snapshots based on satellite status to search for intersatellite link(ISL)construction solutions that meet the minimum number of topology changes to avoid route oscillations.The simulation results in Beidou-3 show that compared with DT-DVTR,MTCR-CR reduces the number of routing changes by about 92%,the number of path changes caused by routing changes is about38%,and the rerouting time is reduced by approximately 47%.At the same time,in order to show our algorithm more comprehensively,the same experimental index test was also carried out on the Globalstar satellite constellation.
基金supported by the Strategic Priority Program on Space Science of the Chinese Academy of Sciences(Grant No.XDA30010200).
文摘The 2:1 resonant distant retrograde orbit(DRO),known for its long-term stability and global accessibility,holds strategic significance in current Earth-Moon space mission explorations.This paper conducts a comprehensive analysis of the problem of low-energy transferring into 2:1 DRO using the weak stability boundary(WSB)and lunar gravity assist(LGA)in the planar bi-circular restricted four-body problem(BCR4BP).The transfer process is categorized into three phases:the Earth-Moon transfer,Sun-Earth weak stability boundary transfer,and DRO low-energy capture.Addressing key questions,our study investigates:(1)Under what LGA conditions can the spacecraft reach the approximate area where the WSB region is situated?(2)How do trajectories,upon reaching the region where the WSB is located,return to the vicinity of 2:1 DRO,potentially facilitating low-energy DRO insertion?Our study involved a comprehensive analysis of the spacecraft’s changes in Earth-Moon mechanical energy and Jacobi energy during the entire transfer process.This analysis yielded the energy and geometric conditions necessary for potential low-energy DRO insertion,effectively filtering out numerous impractical candidate trajectories and enhancing computational effciency.In this paper,the geometric condition is referred to as the low-energy transfer gateway(LETG).Using the LEGT as the stitching interface,a significant number of feasible solutions were obtained effectively for bi-impulse DRO transfer trajectories through differential correction,some of which were previously undiscovered.
文摘The 12th Global Trajectory Optimization Competition challenged teams to design trajectories for mining asteroids and transporting extracted resources back to the Earth. This paper outlines the methods and results of the runner-up team, BIT-CAS-DFH, highlighting an overall analysis of the approach as well as detailed descriptions of the methods used. The approach begins with building databases to reduce computational costs in trajectory design. Then, asteroid sequences are determined. A segmentation-based approach was adopted to efficiently handle the large dataset. Each sequence was divided into four time-based segments. Segments 1 and 4 were generated forward and backward, respectively, using a breadth-first beam search. Candidates for these segments were refined using genetic and greedy algorithms. Segments 2 and 3 were then generated and selected forward and backward based on the results of Segments 1 and 4. Following this, a matching process paired candidates from Segments 2 and 3. With the asteroid sequences established, low-thrust trajectories were optimized using indirect methods. A local optimization strategy was employed to maximize the collected mass by fine-tuning rendezvous timings. The final solution is presented, with comparative analyses against other teams’ approaches.
基金The authors gratefully acknowledge DLR for providing us the opportunity to attend the 27th parabolic flight campaign and Novespace for the support for the test of MAIS by the Airbus A310 ZERO-GThe authors would also like to thank Weijia Ren,Xiaoru Sang,Shimeng Lv,Peng Yang,Yu-e Gao,Lingcai Song,Mengxi Yu,Boqi Kang,Yanlin Zhou,and Anping Wang,who have contributed significantly to the MAIS project.
文摘The Microgravity Active vibration Isolation System(MAIS),which was onboard China’s first cargo-spacecraft Tianzhou-1 launched on April 20,2017,aims to provide high-level microgravity at an order of 10^(-5)–10^(-6)g for specific scientific experiments.MAIS is mainly composed of a stator and a floater,and payloads are mounted on the floater.Sensing relative motion with respect to the stator fixed on the spacecraft,the floater is isolated from vibration on the stator via control forces and torques generated by electromagnetic actuators.This isolation results in a high-level microgravity environment.Before MAIS was launched into space,its control performance had been simulated on computers and tested by air-bearing platform levitation and aircraft parabolic flight.This article first presents an overview of the MAIS’s hardware system,particularly system structure,measurement sensors,and control actuators.Its system dynamics,state estimation,and control laws are then discussed,followed by the results of computer simulation and engineering tests,including the test of the six-degree-of-freedom motion by aircraft parabolic flight.Simulation and test results verify the accuracy of the control strategy design,effectiveness of the control algorithms,and performance of the entire control system,paving the way for operation of MAIS in space.This article also presents the steps recommended for the control performance simulation and tests of MAIS-like devices.These devices are expected to be used on China’s Space Station for various scientific experiments that require a high-level microgravity environment.
基金funded by the National Natural Science Foundation of China(No.61701484)the Research Fund of the Manned Space Engineering(No.18022010301)the Open Fund of State Key Laboratory of Information Photonics and Optical Communications(BUPT)
文摘In our Lett er, we selec ted several commercial optical t ransceivers, which consist of single-channel transceiver modules, parallel transmitting and receiving modules, and Ethernet passive optical network (EPON) optical linet erminal (OLT) and optical net work unit (ONU) modules, to do the total ionizing dose (TID) testing via the gamma-ray radiation method. The changing of current and receiver sensitivity of optical transceivers is discussed and analyzed. Based on the TID testing exposed to a TID of 50 krad (Si) at a dose rate of about 0.1 rad (Si)/s, the performance of single-channel transceivers and parallel receiving modules has not changed after 50 krad (Si) exposure, the parallel transmitting and EPON ONU modules have not worked after 40 krad (Si) and 47 krad (Si) exposure, the EPON OLT module has bit error in the process of irradiation, and it can work well after annealing;the reason for the error of OLT is analyzed. Finally, based on the theoretical analysis and testing results, this Letter provides several design suggestions to improve the reliability for optical transceivers, which can be referenced by satellite system designation for various space missions.
基金funded by the National Natural Science Foundation of China(Grant No.12003054)Strategic Pilot Science and Technology(Project No.XDA3000000).
文摘This study aims to assess the autonomous navigation performance of an asteroid orbiter enhanced using an inter-satellite link to a beacon satellite.Autonomous navigation includes the orbit determination of the orbiter and beacon,and asteroid gravity estimation without any ground station support.Navigation measurements were acquired using satellite-to-satellite tracking(SST)and optical observation of asteroid surface landmarks.This study presents a new orbiter-beacon SST scheme,in which the orbiter circumnavigates the asteroid in a low-altitude strongly-perturbed orbit,and the beacon remains in a high-altitude weakly-perturbed orbit.We used Asteroid 433 Eros as an example,and analyzed and designed low-and high-altitude orbits for the orbiter and beacon.The navigation measurements were precisely modeled,extended Kalman filters were devised,and observation configuration was analyzed using the Cramer-Rao lower bound(CRLB).Monte Carlo simulations were carried out to assess the effects of the orbital inclination and altitudes of the orbiter and beacon as key influencing factors.The simulation results showed that the proposed SST scheme was an effective solution for enhancing the autonomous navigation performance of the orbiter,particularly for improving the accuracy of gravity estimation.
