Aug 2024, Volume 11 Issue 3
    

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  • Research Progress of Technologies for Intelligent Landing on Small Celestial Bodies
    LIANG Zixuan, LU Bingjie, CUI Pingyuan, ZHU Shengying, XU Rui, GE Dantong, BAOYIN Hexi, SHAO Wei
    2024, 11(3): 213-224. https://doi.org/10.15982/j.issn.2096-9287.2024.20240035
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    To meet the robust landing requirement in the exploration and exploitation of small celestial bodies，based on the landing exploration missions in China and abroad，the requirements of intelligent landing technologies were analyzed and the corresponding research progress was discussed. Firstly，the landing exploration missions for small celestial bodies were reviewed. Then，the traditional rigid landing mode and the novel intelligent flexible landing concept of small celestial bodies were introduced，and the intelligent technology requirements of small celestial body landing were sorted out. On this basis，the research progress on intelligent landing technologies was summarized from the aspects of dynamics，mission planning，perception，navigation，guidance and control. Finally，the development trend of landing technology of small celestial bodies is envisioned.
  • Non-Uniform Constraints Processing for Multi-Node Flexible Lander
    CHAI Jingxuan, WU Xinyu, GONG Youmin, MEI Jie, MA Guangfu
    2024, 11(3): 225-232. https://doi.org/10.15982/j.issn.2096-9287.2024.20230136
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    To address the issue of non-uniform constraints in the cooperative descent trajectory planning of the novel multi-node flexible lander, a distributed optimization method based on control barrier functions is proposed. This method requires only relative distance information between nodes to solve the conflict-free descent trajectories for each node. The effectiveness of the proposed method is demonstrated through simulations of two typical scenarios of cooperative descent of the multi-node flexible lander. This approach offers a new perspective for addressing the non-uniform constraints problem of the multi-node flexible lander.
  • Adaptive Curvature Guidance for Flexible Landing on Small Celestial Bodies
    ZHAO Dongyue, ZHU Shengying, CUI Pingyuan
    2024, 11(3): 233-243. https://doi.org/10.15982/j.issn.2096-9287.2024.20240030
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    Flexible landing is a new way to prevent rebound and overturning in weak gravity environments of small celestial bodies and improve landing safety on these bodies. To realize obstacle avoidance of the flexible lander during the landing process，an adaptive curvature guidance method combined with convex programming and the concept of virtual safety boundary was proposed. Based on the geometric convex trajectory obtained through curvature guidance，a virtual safety boundary related to the structural characteristics of the flexible lander was constructed. The shape of the boundary was adaptively adjusted according to terrain obstacle information，and the optimal obstacle avoidance trajectory was solved via successive convex programming technique. The result of numerical simulation shows that the method proposed in this paper possesses satisfactory obstacle avoidance capability for the flexible landing mission in complex terrain conditions，which further improves the landing safety on small celestial bodies.
  • Multi-Agent Reinforcement Learning Autonomous Task Planning for Deep Space Probes
    SUN Zeyi, WANG Bin, HU Xinyue, XIONG Xin, JIN Huaiping
    2024, 11(3): 244-255. https://doi.org/10.15982/j.issn.2096-9287.2024.20230159
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    To meet the requirements for autonomy，rapidity，and adaptability in the collaborative planning of each subsystem during the attachment mission of a deep space probe，a collaborative planning strategy based on proximal policy optimization method and multi-agent reinforcement learning was proposed. By combining the single-agent proximal policy optimization algorithm with the hybrid collaborative mechanism of multi-agent，a multi-agent autonomous task planning model was designed. The noise-regularized advantage value ws introduced to solve the problem of overfitting in the collaborative strategy of multi-agent centralized training. Simulation results show that the multi-agent reinforcement learning collaborative autonomous task planning method can intelligently optimize the collaboration strategy of small celestial body attachment missions according to real-time environmental changes，and compared with the previous algorithm，it improves the success rate of task planning and quality of planning solutions，and shortens the time of task planning.
  • Research on Asteroid Flexible Landing with Object-Oriented Attitude Planning
    ZHU Zhe, XU Rui, WANG Xiaoyan, LI Zhaoyu, ZHU Shengying, LONG Jiateng, GAO Yue
    2024, 11(3): 256-264. https://doi.org/10.15982/j.issn.2096-9287.2024.20230088
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    In order to solve the problem of attitude maneuvering control and attitude planning for the flexible probe under multiple constraints in the asteroid flexible attachment scenario，in this paper, a goal-oriented attitude planning method for an asteroid-attached flexible probe was proposed. By constructing a node-plane coupling dynamic model, the attitude description and dynamic constraint characterization of the flexible three-node probe were realized. A local optimization expansion strategy was designed to improve the RRT algorithm. The optimization objective was to shorten the distance to the target attitude. The quadratic programming problem was constructed by combining with the attitude dynamics model of the flexible body to enhance the purpose of maneuvering along the attitude path. The simulation results show that compared with the traditional heuristic planning method, the proposed method takes less time to calculate, optimizes the attitude maneuver path length, and can meet the attitude maneuver requirements during the flexible landing process of the asteroid probe. It provides support for the implementation of the small body project.
  • Attitude-Orbit Coupling Intelligent Control of Flexible Asteroid Lander
    SUN Yiyong, ZHENG Heming, ZHAI Guang, LI Jie, WANG Yanxin
    2024, 11(3): 265-273. https://doi.org/10.15982/j.issn.2096-9287.2024.20230171
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    A method for attitude-orbit coupling intelligent control of flexible lander based on maximum entropy reinforcement learning is proposed in this paper，aiming at solve the adverse effects of the complex perturbation environment and the inaccurate flexible deformation force. Firstly，the orbital dynamics model of the equivalent agent is established by introducing the internal flexible force of the lander. The datum plane method is used to characterize the attitude of the flexible lander with complex deformation. The attitude-orbit coupling dynamic environment of the lander is constructed to train the intelligent controller. Then，an intelligent controller with deep neural network architecture is designed according to the soft actor-critic（SAC）algorithm of maximum entropy reinforcement learning theory. Each thruster can keep the lander attitude stable and track the navigation trajectory with high precision by self-adapting the output thrust. Finally，the landing process with the controller deployed is simulated. The simulation results show that compared with the classic PD control method，the intelligent control method proposed in this paper has stronger robustness.
  • Prior Pose Correction for Asteroid Landing Based on Feature Tracking Assistance
    WANG Yaqiong, XIE Huan, YAN Xiongfeng, WANG Yifan, CHEN Jie, TONG Xiaohua
    2024, 11(3): 274-285. https://doi.org/10.15982/j.issn.2096-9287.2024.20230151
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    Aiming at the possible inaccuracy of the prior pose during the visual navigation of an asteroid landing，a feature tracking aided pose estimation method is proposed. First，the generation of navigation features relies on pre-existing pose information and a database of navigation features. Subsequently，a multi-feature discriminative correlation filter (DCF) is employed to track the position of the navigation features in the navigation camera images by combining handcrafted and depth features. The average peak correlation energy (APCE) is subsequently employed to effectively screen dependable tracking outcomes for the initial estimation of the pose. Finally，the navigation features are recalculated using the initial estimation of the pose and adjusted to match with the navigation camera image by using normalized correlation coefficients (NCC). The proposed methodology involves the integration of the process within a differentiable Levenberg-Marquardt (LM) framework， specifically designed for pose optimization. This framework incorporates constraints based on the NCC. Experimental results， utilizing images，terrain, and ephemeris data obtained from the Osiris mission，demonstrate that the proposed method's pose estimation exhibits reprojection errors within the sub-pixel range. At 1 km from the asteroid surface，the position estimation error is within 2 m and the attitude estimation error is within 1°.
  • Morphology Feature Rapid Selection for Asteroid Landing
    XIU Wenbo, HE Ying, ZHU Shengying, LIU Yanjie
    2024, 11(3): 286-294. https://doi.org/10.15982/j.issn.2096-9287.2024.20240036
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    Given the complex and numerous morphological features during asteroid landing，which lead to challenges such as huge number of feature combinations，high computational load in online feature selection and low computational efficiency，in this paper an online multi-type feature rapid selection method was proposed. Using rapid selection criteria for multi-type features combined with search region，a method for selecting single-frame image features was established. Additionally，considering the short sampling interval，high inter-frame image overlap，and high feature inheritance probability during asteroid landing，a method for inter-frame image feature inheritance selection was proposed. Simulation experiments show that the design of single-frame image search regions and inter-frame image feature inheritance methods substantially reduces the number of feature combinations，thereby greatly enhancing the efficiency of computational and online feature selection.
  • Relative Navigation Observation Sequence Planning for Small Body Attachment and Its Experiment
    LI Jiaxing, WANG Dayi, DENG Runran, GE Dongming, DONG Tianshu
    2024, 11(3): 295-303. https://doi.org/10.15982/j.issn.2096-9287.2024.20240039
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    In the process of small body attachment detection，due to the limitation of computational resources，it is difficult for the sequence image autonomous relative navigation system to process a large amount of optical image information. In this paper，a relative navigation observation sequence planning method is proposed，and an observable measurement index describing the observation accuracy of the landmark is established based on the Fisher information matrix，which is used as an index to design the observation strategy for the preferred selection of the key observation moments. In order to verify the validity of the relative navigation method，a small body attachment experiment platform is constructed，and the 6-degree-of-freedom attachment motion simulation of the lander is realized by pulling the load platform with 8 ropes in parallel. Finally，a visible light camera is mounted on the experimental platform to realize the semi-physical simulation of the relative navigation of small body attachment，which greatly reduces the computational burden of the navigation system while providing high-precision relative navigation. It will provide reference for the asteorid project in the future.
  • Scientific Objectives and Payloads Configuration of the Tianwen-2 Mission
    LI Chunlai, LIU Jianjun, REN Xin, YAN Wei, ZHANG Zhoubin, LI Haiying, OUYANG Ziyuan
    2024, 11(3): 304-310. https://doi.org/10.15982/j.issn.2096-9287.2024.20230185
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    In this paper，scientific objectives and payloads configuration of international asteroid exploration missions in the past three decades were reviewed. On the basis of summarizing the main scientific questions of asteroid exploration， the selection of detection objects，scientific objectives and payloads configuration of China’s asteroid exploration project，which named Tianwen-2 mission were discussed. Focusing on the realization of scientific objectives，corresponding scientific research contents and payload technical specifications were proposed.