CBERS-2B satellite’s scheme was switched from zero-momentum control to biased-momentum control and magnetic control by uploading the control program to AOCC, when the main gyros were invalid. The implementation of biased-momentum control is described and the telemetry data analysis is supplied to evaluate the satellite’s flight. It was a successful experience for this kind of satellites to settle a stable flight with high reliability under the failure of crucial devices such as gyro, momentum wheel.

Lagrangian coherent structure (LCS) is defined by means of ridges of finite-time Lyapunov exponent (FTLE) fields in this paper. Moreover, a relation between LCS and time-dependent invariant manifold is obtained. Taking LCS as a tool, the property of the invariant manifold in elliptic restricted 3-body problem (ER3BP) is achieved numerically: time-dependent invariant manifold is an invariant set of orbits and acts as the separatrix of transit-orbit set and non-transit orbit set.

From the perspective of molecular dynamics simulation, we present a distributed control strategy that lets a swarm of spacecraft autonomously form a lattice in orbits around a planet, just making use of limited local sensory information. The strategy is based on the artificial potential field approach, which divides the artificial field into two parts: a global artificial potential field mainly based on the famous C-W equations that gathers the spacecraft around a predefined meeting point, and a local term exploiting the well-known Tersoff-Brenner potential that allows a spacecraft to place itself in the correct position relative to its closest neighbors. Moreover, in order to ensure convergence for all initial distributions of the spacecrafts, a dissipation term depending on the velocity of the agent is introduced. The new methodology is demonstrated in the problem of forming a regular tetrahedron lattice (include the center), i.e., the structure unit of diamond. By slightly changing the scenario, our method can be easily applied to shape other configurations similar to the structures of allotropes of carbon, e.g., a regular hexagon(i.e., the structure unit of graphite) etc.

Upon the demands of high accuracy, high reliability and real time for interplanetary navigation system, an autonomous navigation method for the approach phase is proposed, which relies on the onorbit fusion of optical and radio measurements. To choose appropriate optical measurements and radio measurements for on-orbit fusion, the paper, using a linear covariance analysis and an error analysis method based on B-plane parameters, analyzes various autonomous navigation schemes fusing different optical and radio measurements. The result shows that the proposed autonomous navigation method can effectively improve the navigation accuracy. We also give some principles for reasonable selection of optical measurements. Finally, the presented analysis method is verified by the Monte Carlo target practice based simulation.

In order to reduce the chattering of variable structure control for flexible spacecraft attitude, an improved sliding mode controller is presented. Based on the boundary-layer sliding mode controller, the more smooth “arctan function” is used to replace saturation function to reduce the chattering. The delay factor is introduced in the reaching-law of sliding mode controller to reduce the maximum control torque required by the system at the initial maneuver moment, which can avoid the vibration of flexible appendages. Simulation results show that the improved sliding mode controller not only can effectively reduce chattering but also has strong robustness against parametric uncertainties.

Based on the temporal analytical redundancy between the available star sensor and gyro measurements, two filters are utilized to isolate the star sensor faults in a threeaxis stabilized attitude control system with two star sensors. Considering that gyro measurement noise is multiplicative noise in the attitude kinematics equations, a residual generator based on the linear minimum mean square filter is designed to obtain residuals containing the fault message of the target star sensor. The target star sensor fault detection is realized by comparing the residual evaluation with the corresponding thresholds, which is computed according to the residual variances in fault free case. Star sensor faults are located by setting one sensor as the target each time and checking the detection logic afterwards. Numerical simulation results show that either abrupt faults or slow degradation of the measurement accuracy of star sensors can be isolated by the designed method.

Abstract：Aiming at orbital maintenance of the Walker constellation configuration in medium earth orbit considering the effects of orbital perturbation, we discuss the excursion of the constellation configuration. After this, the long-time maintenance control methods and the control strategy of the constellation configuration are discussed. The perturbation penalty method has been analyzed. The numerical differential modified method of the constellation configuration is presented and discussed. Finally, the long-time orbital control strategy for global constellation is presented and simulated. Simulation analysis shows that the constellation configuration numerical differential modified method can achieve higher control calculation accuracy than constellation configuration perturbation penalty method.

In this paper, we analyze the dynamic characteristics of a spacecraft in low gravity with spherical tanks. The dynamic model of fuel sloshing is equivalent to a usual pendulum model. The state variables of the system are divided into two parts. In the case that three important parameters change with the fuel consumption, an adaptive hierarchical sliding-mode controller is designed in this paper. Using the Lyapunov method, parameter adaptive laws are derived, which guarantee the stability of the closed-loop system .The simulation results show that the system can achieve attitude tracking precision in a short time, as well as the fuel slosh is effectively suppressed.

Optimization design method for flywheel’s sealed cover is studied in this paper. Above all, the design schemes for constructing outline curve of sealed cover using convex concave arcs are comprehensively analyzed. Then a scheme for designing the outline curve consisting of concave arc and convex arc is proposed. Based on the above, the extremum values of arcs are derived and a series of structural models are constructed. Finally, taking the sealed cover of a flywheel as an example, the varying rules of the stability corresponding to the outline parameters are studied using finite element approach. The new design scheme can provide instructions for the design of similar structures.

According to the principle of traditional east-west station-keeping, we develop a new strategy of east-west station-keeping using fixedperiod continuous impulsive maneuver for geostationary satellite in this paper. Based on the analysis of perturbation, the control flow and the control parameters are designed. The effects on orbit parameters, attitude control and angular momentum management are analyzed. Evolutions of semi-major axis, eccentricity and mean longitude for one year are simulated by a realistic example. Simulation results indicate that the satellite’s mean longitude is kept in tolerance window for a long time. The new strategy has the advantage in its simpleness of control flow and in its accuracy of station keeping.

The vane type tank with big vanes is one of the most advanced new type propellant tanks now. The big vanes are the core components of propellant management in the tank. The numerical simulation and microgravity experiment verification of fluid behavior in the tank are given. By using a VOF twophase flow model, the fluid flow characteristics in the tank are numerically simulated, and the fluid distributing rule is obtained. A microgravity test system is established. Based on fluid behavior experiment on microgravity drop tower, some important conclusions are obtained. The results show that, the tank has good performance of propellant management in microgravity environment, and the big vanes provide a better approach for liquid (including cryogenic liquid) control in space environment. In this paper, the numerical simulation and microgravity test provide necessary foundational data for the design of vane type tank.