Apr 2021, Volume 8 Issue 2
    

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  • Topic：Autonomous Planning Technology for Deep Space Exploration
    Research Progress of Autonomous Planning Technology for Deep Space Probes
    XU Rui, LI Zhaoyu, ZHU Shengying, WANG Bang, LIANG Zixuan, SHANG Haibin
    2021, 8(2): 111-123. https://doi.org/10.15982/j.issn.2096-9287.2021.20210039
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    In the process of deep space exploration，the probe has a long flight distance and is in dynamic environment. Traditional ground station telemetry and remote control methods can hardly meet the requirements of real-time，robustness and safety of the probe control. It is urgent for the probe to have autonomy，and autonomous planning technology is one of the key technologies to realize the autonomous operation of the probe. The article introduces the development of autonomous planning technology and the connotation of autonomous planning for deep space probes，summarizes and analyzes key technologies from the framework of planning and execution，planning model，mission planning，replanning，motion planning and scientific observation mission planning，and proposes the development direction of autonomous planning based on technological development and mission requirements.
  • Topic：Autonomous Planning Technology for Deep Space Exploration
    Fast Mission Plan Repair Method for Mars Rover Based on State Difference
    CHEN Chao, XU Rui, LI Zhaoyu
    2021, 8(2): 124-131. https://doi.org/10.15982/j.issn.2096-9287.2021.20200075
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    The uncertainty of Mars environment and the difficulty to predict the failure of electronic equipment will seriously affect the actual effect of the pre-designed plan of the rover on Martian surface，resulting in plan execution failure. To solve this problem，a fast mission plan repair method based on state difference is proposed based on the fact that there is long delay between the Mars rover and the ground station. This method constructs partial states at different times by extracting the key information from the existing plan，lying on the difference between the perception state and the necessary state of action execution. And then the rapid mission plan repair strategy for Mars rover based on the partial state is presented. In this strategy，to improve the efficiency of plan repair，the search space deletion method based on the state difference between the actual state and the partial state is proposed. Simulation results demonstrate that this method can not only improve the efficiency of mission plan repair，but also ensure the plan stability.
  • Topic：Autonomous Planning Technology for Deep Space Exploration
    Asteroid Landing Trajectory Dynamic Planning Method with Complex Topography Adaptability
    GE Dantong, ZHU Shengying
    2021, 8(2): 132-139. https://doi.org/10.15982/j.issn.2096-9287.2021.20200072
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    Considering the safety threats posed by the complicated topography on the asteroid surface，a dynamic planning method for topography-adaptive landing trajectory is proposed. In this paper，a multi-objective optimal waypoint sequence is developed for the landing process. Based on the hazard detection information，an online evaluation of the collision threats is carried out. To solve the conflicts between hazards and the nominal trajectory，a minimum waypoint re-planning method is designed，which realizes an autonomous switch between waypoint robust tracking and dynamic planning of the local hazard avoidance trajectory during descent. By employing the proposed method，adaptability to the complex topography environment of the lander is enhanced and the asteroid landing mission safety is improved.
  • Topic：Autonomous Planning Technology for Deep Space Exploration
    Research of a General Teleoperation Task Intelligent Planning Method
    GAO Yuhui, SHI Ming, CAI Dunbo, ZHANG Gong
    2021, 8(2): 140-146. https://doi.org/10.15982/j.issn.2096-9287.2021.20200071
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    Based on the technical challenges of teleoperation tasks in China，a general task intelligent planning method with hierarchical plan object model（HPOM）is proposed，which decomposes the task of rover into four levels: multi option operation，constrained behavior，multi branch instruction sequence and parameterized virtual instruction. The plan represented by constrained behavior is transformed into a behavior planning problem，and a set of solving methods is obtained to solve the practical problems such as difficult selection of multi branch operation and complex setting of event attributes under complex constraints. A process flow of human-in-the-loop（HITL）is proposed to verify the consistency of different planning granularity schemes and generate instruction sequence. This method has been successfully applied to Chang'E-4 mission，providing technical support for the success of the mission.
  • Topic：Autonomous Planning Technology for Deep Space Exploration
    Combination Planning for Attitude Maneuver of Deep Space Probes Based on Multi-Objective Optimization
    WANG Zhuo, XU Rui
    2021, 8(2): 147-153. https://doi.org/10.15982/j.issn.2096-9287.2021.20200069
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    For deep space detectors attitude maneuver tasks，it is necessary to optimize several performance index parameters. In this paper，the multi-objective planning problem of attitude maneuver for deep space detectors is studied，and a multi- target combination planning method is proposed to calculate the attitude maneuver path. For multi-objective programming，the attitude objective function is designed through physical planning method，which transforms multi-objective optimization into a single objective planning problem，and at the same time replaces fitness function as the population selection criterion. The combined differential evolution algorithm is designed to improve the mutation process. The initial attitude path obtained by fast Euler maneuver is added to the mutation formula with a certain probability，so as to improve the convergence rate and program operation efficiency，and realize the multi constraint and multi-objective attitude maneuver path combination planning. Finally，the feasibility and effectiveness of this method are verified by numerical simulation of large angle attitude maneuver of deep space probes.
  • Article
    Communication-Navigation Integrated Technology and Its Application in Lunar Exploration
    XIE Haoran, ZHAN Yafeng, WANG Xiaowei, CHEN Xi
    2021, 8(2): 154-162. https://doi.org/10.15982/j.issn.2096-9287.2021.20200087
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    Satellite communication-navigation integrated technology allows users to achieve communication and navigation at the same time. Compared with an autarkical and independent satellite communication or satellite navigation system，a communication-navigation integrated system is more comprehensive. At present，BeiDou Navigation Satellite System can provide radio navigation service and radio data service，and most satellites in the world can also measure the distance between satellite and ground station during communicating，even providing time base for satellite. However，there is still a long way to go from these existing practices to the ideal integrated communication and navigation system. Based on satellite communication，a new integrated communication-navigation architecture is proposed，and a case of using the lunar relay communication system to achieve lunar navigation in the setting of manned lunar exploration was given. The simulation results show that the proposed communication and navigation integrated system not only provides communication services，but also provides high precision positioning and timing services for the users on the lunar surface.
  • Article
    Research on Adaptive Guidance Technology for Lunar Emergency Ascent
    ZHAN Kangyi, CHEN Haipeng, YU Xuehao, WANG Lu, LI Zewen
    2021, 8(2): 163-170. https://doi.org/10.15982/j.issn.2096-9287.2021.20200076
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    In this paper，an adaptive guidance method is studied for the emergency ascent of the lunar surface. Firstly，according to the principle of maximum value，the two-point boundary value problem of maximum energy entering orbit under five constraints is derived and established. Secondly，a two-layer iterative solution strategy is designed. The inner layer uses Newton iteration to solve the two-point boundary value problem of maximum energy into orbit，and the outer loop adjusts the time to make the speed meet the target speed. In the outer loop iteration，a time iterative adjustment strategy is designed. In the inner loop，according to the change rule of the thrust direction in the task，a strategy for selecting the initial value of the principal vector of the covariant variable is designed to solve the two-point boundary value problem. The simulation results show that the guidance law designed in this paper can converge reliably，and the target parameter binding is simple. It can adapt to coplanar ascending tasks and different-plane ascending tasks. In the presence of second consumption and specific impulse deviation，it still has high guidance accuracy.
  • Article
    Central Difference Convexification Method for Soft-Landing Trajectory Optimization in Planetary Powered Descending Phase
    LI Mingxiang, PAN Binfeng
    2021, 8(2): 171-181. https://doi.org/10.15982/j.issn.2096-9287.2021.20200079
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    Aiming at the mission of real-time online guidance for fixed-point soft landing on planet，the paper designs an algorithm based on sequential convex optimization that is designed to solve the fuel-optimal trajectory. The pre-labeled central difference algorithm is used to linearize the dynamics equations and the termination condition based on the deviation of index is proposed to judge whether it converges，which can generate a fuel-optimal trajectory quickly. Besides，a fitting function is given to approximately estimate the optimal terminal time by analyzing the relationship between the terminal time of optimal trajectories and their remaining fuel，which can reduce the amount of unknown variables. The simulation results of this algorithm show the weak sensitivity to initial guess，good convergence and small terminal error compared to the traditional convexification method of linearizing the dynamics equations whose variables are substituted at first.
  • Article
    Simulation and Analysis of Orbit Determination of Space Gravitational Wave Detector
    LI Kangkang, GU Defeng, AN Zicong, SONG Jianing, ZHU Jubo
    2021, 8(2): 182-189. https://doi.org/10.15982/j.issn.2096-9287.2021.20200081
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    Aiming at the precise orbit determination of Space gravitational wave detector，LISA（Laser Interferometer Space Antenna）is selected as the research object to establishs the target simulation environment，detect simulates the generation of the ranging and velocity measurement data at different stations by American Deep Space Network（Deep Space Network）Network（DSN） and China Deep Space Network（CDSN）. The accuracy of LISA orbit determination is investigated in terms of the tracking arc length，measurement data types，also the quantity and distribution of ground stations by utilizing the Nonlinear Weighted Least Squares （WLS） and Monte Carlo（MC）methods. The simulation results show that：① Increasing the tacking arc length can effectively improve the orbit determination precision. Moreover，the position accuracy of the estimated detector reaches 92m when the tracking arc is 20 days；② Under the current measurement accuracy，the performance of the LISA orbit determination is considerably determined by the ranging data. The combined ranging/Doppler orbit determination method gains a growth of 32.23% and 99.52% estimating position accuracy，compared with the only ranging and only Doppler orbit determination strategies，respectively；③ By utilizing multiple deep space networks，the common viewing rate of multi stations increases markedly，improving the accuracy and the convergence of the orbit determination. The performance of the joined DSN/CDSN orbit determination scheme is compared to the only DSN scheme by different arc lengths，with an increment of the average position accuracy of 43.73%.
  • Article
    A Fast Star Angle/Time Delay Measurement Integrated Navigation Method
    GUI Mingzhen, NING Xiaolin, MA Xin, YE Wen
    2021, 8(2): 190-197. https://doi.org/10.15982/j.issn.2096-9287.2021.20200080
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    The time delay based on solar oscillation is a new type of celestial navigation measurement. Combined with the star angle measurement, it can improve the navigation performance. However, the ephemeris error of Phobos will reduce the navigation accuracy. To solve this problem, a fast star angle/time delay measurement integrated navigation method is proposed. The position and velocity of Phobos are estimated online to suppress the effect of Phobos ephemeris error on the estimation accuracy of star angle/time delay measurement integrated navigation. The amplitude of the innovation is tested by setting a threshold，and the implicit unscented Kalman filter based on time delay measurement is selectively performed，which greatly improves the real-time performance of navigation. Simulation results show that the proposed method can significantly improve the real-time performance of navigation while ensuring navigation accuracy.
  • Article
    Autonomous Relative Navigation Based on Sequential Image Measurements of Unknown Landmarks
    XU Chao, HUANG Xiangyu, LI Maodeng
    2021, 8(2): 198-204. https://doi.org/10.15982/j.issn.2096-9287.2021.20200086
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    An autonomous relative navigation method based on sequential image measurements of unknown landmarks for planetary landing in unknown environment is presented. In the proposed method，the line-of-sight vectors of landmarks with unknown 3D positions tracked in three sequence images and position information derived from inertial measurement unit at the time instances of the three images are used to develop implicit measurement constraints. An implicit extended Kalman filter tightly integrates the constraints with the measurements from IMU to estimate the lander's position and velocity relative to the landing site. Numerical simulations of Mars landing indicate the proposed navigation method is efficient and meets the relative navigation requirement of safe planetary landing.
  • Article
    Thermodynamic Analysis of Space Nuclear Power System Based on AMTEC
    ZHANG Yichen, HU Yupeng, WANG Ze, ZHU Changchun, HU Shaoquan, LI Sizhong
    2021, 8(2): 205-212. https://doi.org/10.15982/j.issn.2096-9287.2020.20200045
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    With the development of exploration in deep space，the power demanding for space probe is also increasing. Space nuclear power system based on AMTEC has been paid widely attention due to its excellent characteristics. The mathematical model for exergy analysis of space nuclear power system is presented based on the first and second law of thermodynamics. Futhuremore，according to the specific characteristics of thermal process in the space nuclear power system，the thermal system was divided into six control volumes. The effects of core temperature and electrode current density on the output power and exergy efficiency of total system and six control volume have been studied. And the results can provided guidance for designing and optimizing system performance. The result shows that the increasing of the core temperature shows a positive impact on the output power and exergy efficiency. With the increasing of electrode current density，the output power and exergy efficiency increases first and then decreases，and each core temperature corresponds to an electrode current density where the output power and exergy efficiency are maximum. The largest part of exergy loss is found to be condenser and evaporator through the comparative analysis.