In the present study, a predefined-time attitude stabilization for liquid-filled spacecraft with large liquid sloshing is investigated under input saturation and external disturbance. First, the large slosh of the liquid is equivalent to the motion pulsating ball model (MPBM), and the dynamic model of the rigid-liquid coupling system is established. Then, liquid sloshing state quantity-related items and external disturbances are combined to form a lumped disturbance. A predefined-time disturbance observer is proposed to accurately reconstruct the lumped disturbance within a predefined-time regardless of the initial estimated state. Based on the proposed predefined-time disturbance observer, a predefined-time sliding mode surface is designed. The predefined-time stability of the proposed observer and controller is proved using the Lyapunov function. Finally, a variable-speed reaching law and exponential reaching law are combined to suppress the chattering caused by sliding mode control. To this end, a new auxiliary function is developed to consider the effects of input saturation. The simulation results show that the proposed controller can effectively stabilize the attitude stability of the liquid-filled spacecraft.
Focusing on cutting-edge scientific issues related to lunar exploration and applications, 9 overarching goals and 38 specific objectives for China's manned lunar exploration program have been proposed. Leveraging China's technical capabilities in manned spaceflight and lunar exploration, as well as its expertise in lunar and planetary science, the objectives center on scientific research, lunar-based scientific research, and resource exploration and utilization. Based on these scientific goals and trends in domestic and international manned lunar exploration landing site selection, China's basic principles and processes for selecting landing sites have been established. Thirty prime landing sites have been identified, including 11 low-latitude regions and 1 mid-latitude region, taking into account scientific value and engineering implementation conditions. These scientific objectives and landing site selection recommendations will serve as important guidance and top-level input for the design and implementation of China's manned lunar exploration program.
Aiming at the speed tracking control problem of micro-nano satellite momentum wheel with parameter uncertainties and external disturbances,a momentum wheel system dynamics model including model uncertainties and external disturbances is established.An adaptive neural network global fast terminal sliding mode control strategy is proposed.Firstly,a global fast terminal sliding mode control strategy is designed to accelerate the system response speed and achieve finite-time stability in the absence of external interference.Then,a radial basis function neural network is used to estimate and compensate for system parameter uncertainty and external disturbances.The neural network adaptive law is derived using Lyapunov method,and adaptive adjustment of the network weights is used to ensure system stability in the presence of disturbances.Finally,the simulation comparison shows that proposed control scheme not only has faster tracking,but also has better anti-interference ability and robustness.
On November 18,2023,SpaceX conducted the second orbital launch test of a Starship carrier rocket at its own launch site.The first stage of the rocket's upward flight was normal and successfully passed the MaxQ.The first and second stages of the rocket successfully completed thermal separation.Subsequently,multiple engines of the first stage malfunctioned during the flipping process,eventually exploding and disintegrating.The second stage experienced engine abnormalities after flying for several minutes,and the rocket ultimately triggered self destruction and failed to reach the predetermined orbit,resulting in a failed launch.Based on the relevant research content,the abnormal phenomena that occurred during the launch of the first and second stages of the rocket were sorted out,and the possible causes of abnormal phenomena and flight failures were analyzed.The experience and inspiration for similar rocket systems were summarized.
Aiming at the strong atmospheric drag torque and attitude control actuator failure of ultra-low-orbit satellite,a method to estimate and compensate the disturbance and fault is proposed based on the theory of concurrent learning strategy.Firstly,as an idea for parameter identification,the concurrent learning adaptive identification strategy is introduced into the problem of disturbances and faults estimation.Compared with traditional observers,the proposed strategy can estimate the disturbances and faults simultaneously and separately,and the attitude information and command torque are not required at all time.Then,based on the estimations,an attitude controller is designed to guarantee high precision of attitude control of the satellite with external disturbances and actuator faults.Finally,a set of numerical simulations of specific mission process is carried out to verify the effectiveness of the proposed method.
In order to solve the major problem of strategic resources faced by the sustainable development of the Earth and the significant challenge of in-situ resource supply for large-scale space exploration,space resource exploitation has become one of the cutting-edge hot focuses currently.On the basis of clarifying the concept and connotation of space resource exploitation,in-depth analyzing of the current situations and trends of technological development,combining with the resources distribution characteristics of solar system,a solar system resource exploitation architecture and the initiative"Tiangong Kaiwu"are proposed.With the exploitation of strategic mineral resources closely related to the development of human society as the core,the development of water-ice resources and water-based propulsion preparation as the basis,the capacity of solar system resource exploitation can be gradually built step by step.Taking the Earth as the center,from near to far,the lunar resource exploitation architecture,NEA mining architecture,Mars resource exploitation architecture,main-belt asteroids mining architecture,Jovian planets exploitation architecture and the inner planets exploitation architecture will be developed to gradually build the capacity to exploit resources throughout the solar system.
A parametric adaptive convex optimization lunar landing trajectory planning algorithm based on the optimal observer is proposed for the lunar surface descent landing problem with high accuracy.Firstly,to address the need of minimizing fuel consumption in the main deceleration section of the descent landing,the lunar surface descent landing problem is transformed into a second-order cone planning problem by considering the constraints and the nonconvexity of the dynamical model using a lossless convexification technique;secondly,an optimal observer based on the Riccati equation is designed to reduce the influence of the uncertainty of parameters such as mass and specific impulse during the descent landing process;then the optimal trajectory generated according to the nominal parametric convex The optimal trajectory generated by the optimization is then flown,and the online real-time estimation of the lander parameters is achieved by using the real-time accelerometer measurement information in the process,combined with the thruster output information;after the convergence of the parameter estimation is achieved,the online planning of the optimal trajectory is realized by solving the second-order cone planning problem online.The simulation results show that the observer can achieve online parameter estimation in real time;the algorithm only needs the engine to have a discrete thrust domain compared with other fixed-point landing algorithms,and has the advantage of higher accuracy.
Aiming at the problem of trajectory and multi-dimensional deformation integration real-time planning of morphing vehicle,an intelligent planning method based on object layered architecture was proposed.Firstly,by designing pseudo control variables as intermediate variables,the trajectory and deformation integration planning problem of morphing vehicle is decoupled into two sub-problems:trajectory planning at the upper level and decision-making at the bottom level.Then,for the upper-level trajectory planning problem,considering the random reentry point and random target position of the vehicle,the deep neural network model was established from the current state to the trajectory control quantity.The large-scale optimal trajectory samples were obtained offline based on the pseudo-spectral method,and the error back propagation method was used to train the deep neural network model.Aiming at the decision-making problem of the bottom control quantity,the reward function is established from the demand optimal aerodynamic parameter instruction output by the upper-level network.Deep deterministic policy gradient algorithm is used to train the agent,forming a deep network model from the optimal aerodynamic parameter instruction to the trajectory control quantity and multidimensional deformation quantity.Finally,the proposed method is verified by simulation.The results show that the proposed method can quickly generate the optimal trajectory and the sequence of deformation and control variables.Compared with the traditional trajectory optimization algorithm,the proposed method can directly plan the multidimensional control variables and shorten the calculation time by about 94%,which can meet the requirements of online trajectory and deformation integrated intelligent planning.
From the perspective of on-orbit application,this paper reviews the recent progress of spacecraft pose estimation based on deep learning.First,the progress and limitations of traditional artificial features are summarized.On this basis,the significance of deep-learning-based methods are drawn out,and the key problems and solutions of deep learning-based methods in the present and future are expounded in terms of open competitions,datasets,pose estimation methods,and open-source models.Then the subsequent development directions and ideas of the corresponding key technologies are given from the three aspects of realism of datasets,deployability of models and multi-task domain adaptation.
The key algorithms are proposed for autonomous mission planning of agile satellite active push-broom imaging(APBI).Firstly,the vertical strip division algorithm of area target is designed in terms of the payload imaging width and satellite orbit.Secondly,the non-parallel strip imaging trajectory model is established,which is continuously differentiable and describes the relationship between the observation position and the imaging time,and then the three-axis attitude planning algorithm for APBI is deduced.Thirdly,to exploit the maximum maneuvering ability of the satellite,the algorithm for getting the shortest attitude maneuver time between APBI tasks is proposed based on a sixth-order polynomial attitude maneuver model.Then,the two-level task scheduling algorithm is proposed,including earliest-observation sequence search based on branch and bound algorithm and two kinds of pruning rules,and observation sequence best window translation in reverse order.On the basis of maximizing the observation quantity,the imaging quality is adjusted to the optimum.Finally,the simulation experiments are carried out on the onboard processor and the simulation results demonstrate the correctness and effectiveness of all the proposed algorithms.
Considering the dynamic communication processing between networks when monitoring UAV(Unmanned aerial vehicle)cluster network in marine application scenario,the key technologies of UAV cluster network communication is studied,from the aspects of routing,high dynamic random access and dynamic resource scheduling.A clustering DSDV(Destination sequenced distance vector routing)routing protocol is designed,which dynamically allocates network bandwidth to each cluster according to the requirements of task types,so as to improve the network performance.Apart from this,a distributed high dynamic random access protocol with on-demand distribution and a dynamic resource management method based on proportional fairness algorithm are designed,to solve the uncertainty problem of UAV cluster sub-nodes when accessing and exiting,and effectively avoid the conflict of multiple access requests in the communication process.The results show that the networking communication terminal designed by this method has a large margin compared with the cluster communication requirements,and can meet the requirements of UAV cluster communication in the sea area.
For the push-broom imaging in the shadow area,the ground speed of the imaging area of the optical push-broom satellite is too fast,which makes it difficult to obtain high-quality night images.This paper designs an active ground velocity proportional reduction push-sweep imaging attitude planning method to address the issue of insufficient sensor integration time for the fast ground velocity.Firstly,the equivalent orbit initial position of the satellite for imaging with proportional ground velocity reduction is calculated based on parameters such as the maneuver time,imaging start time,and velocity reduction ratio of the push-broom imaging mission.Secondly,the real-time coordinates from the satellite optical axis to the ground target point are calculated by orbit propagation based on the equivalent orbit initial position and the attitude of satellite.Then,the real-time desired attitude of the satellite pointing to the ground target point is calculated based on the actual orbit position and attitude of satellite.Finally,numerical simulations and on-orbit tests of the proposed method are conducted by using the satellite parameters of Jilin-1-GF04A,and the results demonstrate the feasibility and effectiveness of the method.
Aiming at the technical requirements of non-ascertained and non-structural surface safe and stable attachment of small celestial bodies,a series-parallel hybrid mechanism is designed,which can realize passive self-adaptation to the terrain of the star catalog in the grasping area on a total of six degrees of freedom of offset and torsion at the same time,and its workspace optimization is completed.Firstly,a design scheme of 3-RSPS serial-parallel hybrid passive adaptive mechanism is proposed to solve the problem that the attachment device and the star table fitting sphere are not centered during the attachment process.Furthermore,the modified G-K formula is used to calculate the degree of freedom of the mechanism,and the inverse kinematics model is derived based on the spatial position vector method.The correctness of the inverse kinematics model is verified by virtual prototype simulation.Finally,the numerical search method is used to complete the fixed attitude workspace analysis and multi-objective optimization based on NSGA-Ⅱ algorithm.The results show that compared with the widely used 3-SPS parallel mechanism,the global workspace of the star terrain adaptive mechanism designed in this paper is improved by 40.9%.After optimization,it is further improved by 21.3%.It can adapt to the more rugged and steep small celestial terrain and has good engineering value.
In order to solve the problem of depth control of trans-media aircraft under the unsteady influence of the acceleration phase,a fast convergence non-singular terminal sliding mode controller based on finite time convergence state observer is designed.Considering the ventilated law of the upper limit of ventilation cavitation instability,the equation of unsteady cavity shape is obtained,and the mathematical model of the acceleration phase of the trans-media aircraft considering the time-varying wetting area of the tail is established,and then it is simplified to the error model oriented by the controller design.In order to deal with the complex disturbance in the system,a finite time convergence state observer referenced by the model is designed to observe and compensate for the system uncertainty,and a non-singular terminal sliding mode controller based on the high order sliding mode reaching law is designed to complete the control system design,the stability of the closed-loop control system is proved by Lyapunov theory.The simulation results show that the controller can effectively suppress the influence of disturbance on the system,and realize the high-precision control of the depth and attitude of the trans-media aircraft considering the unsteady influence of the acceleration phase.
A hybrid simulated annealing genetic algorithm(HSAGA)based on congestion is proposed to solve the tracking,telemetry,and control(TT&C)scheduling problem of large constellations.Firstly,the constraints satisfy problem(CSP)model of TT&C scheduling is established by formally describing various constraints and optimization objectives.Secondly,multi-layer encoding method is adopted to map the TT&C schedule into integer sequence,and genetic algorithm is utilized to perform global optimization.Thirdly,in order to enhance population diversity and expedite convergence,at the end of each iteration,the optimal part of the population is processed with congestion-based simulated annealing.The algorithm is applied on real constellation for TT&C.The constellation consists of over 180 satellites and 32 antennas.The application demonstrates that the HSAGA exhibits a task completion rate exceeding 99%,a normalized integrated gain surpassing 0.9,and a time consumption of less than 15 minutes,thereby validating the algorithm's practical significance.
To solve the inadequacy of Hart-Smith shell adhesive bonded joint model when applied to space membrane structure and the lack of two-dimensional model in high-precision space membrane structure design,membrane adhesive bonded joint models are built and verified.Firstly,a three-dimensional model is built based on Kirchhoff plate theory,and the shear stress and peel stress distribution in the joint are calculated.Secondly,the three-dimensional model is mapped to build a two-dimensional model,and the Young's modulus and strength of the joint are obtained.Finally,the equivalent model is verified by simulation.The difference of Young's modulus between the equivalent model and the simulation is 4.5%～11.8%,and this difference is positively correlated to the width of the joint.The difference of strength of the equivalent model is 29.2%smaller than the difference of Hart-Smith model when the width is 5 mm.The two-dimensional model of membrane adhesive bonded joint provides a foundation for high-precision space membrane structure design.
In view of the fact that reinforcement learning with the characteristic of discrete decision-making can output the optimal sequence of combinatorial optimization problems,a sequence optimization method based on attention model for multi-satellite rendezvous with one spacecraft is proposed to quickly estimate the sequence and time with low transfer cost.The temporal dimension of attention is expanded to make the policy network simultaneously choose the target and time,and the heuristic factor is designed to distribute attention at different times.Then the network parameters are updated based on the REINFORCE algorithm with baseline.For 10-target rendezvous with relatively concentrated orbital distribution,the proposed method is compared with the ant colony algorithm and the mean relative error of the sequence cost is about 9.7%.The calculation time of the learning method is very short,which can be taken as the fundamental support for multi-satellite rendezvous with multiple spacecraft.
针对载人月球探测任务构成系统多、系统交互关系复杂的特点,提出了一种基于模型的多视角分层分析方法.在任务前期(任务概念研究和初步开发阶段),从不同视角对任务层和系统层进行描述,建立任务层和系统层黑盒模型.与基于文档的任务分析方法相比,多视角分层分析方法采用系统建模语言(SysML)对任务进行模型化描述,在任务初期从不同视角对任务和系统进行全面分析.方法采用以模型为中心的思想,支持系统模型快速迭代设计,提高了设计和分析效率.以载人月球探测任务为应用案例,验证了任务内各系统接口匹配情况,并检验了任务逻辑和系统状态设计的正确性.
为实现行星定点着陆,针对E制导和零控位移偏差/零控速度偏差(ZEM/ZEV)制导的不足,提出多约束下动力下降最优反馈制导方法.首先,在分析E制导性质的基础上,提出制导时长初值的高效选取方法和基于预测校正的优化方法,经少量迭代实现在推力范围受限且连续变推力约束下推进剂消耗接近最优.接着,提出基于碰撞规避时长和推力优化分配律的地平碰撞规避方法,并在此基础上利用坐标系旋转,给出满足下滑角约束的碰撞规避方法,显著提高碰撞规避能力和着陆点可见性.之后,提出匀速转动制导和基于预测校正的组合制导参数规划方法,使制导终端扩充满足加速度约束.最后,数学仿真表明新方法有效,多约束适应性强,计算量相对小,适合工程应用.
结合目前卫星姿态控制系统(ACS)故障预测技术的迫切需求,回顾了故障预测技术研究进展,归纳梳理了知识驱动方法和数据驱动方法的特点,总结并指出了卫星姿态控制系统故障预测技术面临的技术难点.在此基础上,重点阐述了知识和数据联合驱动方法在当前和未来的关键问题与解决途径,从知识和数据并行模式、引导模式、反馈模式三个分支给出了相应关键技术后续发展的方向与思路.
