Advances in Astronautics Science and Technology最新文献

The five-skewed single gimbal control moment gyroscope (SGCMG) system, with its superior symmetry and weight advantages compared to the regular pentagonal pyramid configuration, has been widely applied in agile satellites. However, uncertainties in the moment of inertia, actuator installation errors, and other factors induce deviations in control torque execution. Addressing the challenge of avoiding singular states in SGCMGs during attitude maneuvers, this paper proposes a torque direction constrained (TDC) singular avoidance steering law tailored for the five-skewed configuration, solving the non-singular steering problem under control torque deviations. The method determines the optimal initial gimbal angle (IGA) according to the constraints imposed by the five-skewed configuration and designs a robust singular avoidance steering law by introducing torque direction constraints. Simulations demonstrate that the algorithm enables non-singular attitude maneuvers for any zero-angular-momentum initial state.

Large space deployable antennas play a critical role in satellite microwave communications, remote sensing, and deep space exploration due to their high-precision, light weight, and reliability. However, their large size and extremely low stiffness and damping make them susceptible to vibrations, which degrade the stability of antenna beam pointing under continuous external excitation. To mitigate the effects of such vibrations on beam pointing stability, this paper proposes an active hybrid control method targeting beam-pointing-sensitive vibration modes which significantly degrade beam pointing accuracy. First, the dynamic model of the antenna is established, and finite element computing is used to solve the mode shapes and identify the sensitive modes. A model-independent hybrid control method, based on independent modal space control approach, is then designed to control the specific modes, with initial effectiveness verified through numerical simulations. To further validate the practical feasibility of the proposed control method, active vibration control experiments are conducted on a 10 m aperture antenna prototype for a specific beam pointing sensitive mode (approximately 4.6 Hz). Experimental results indicate that steady state vibration is achieved within 1.1 s after initiating active control, with root-mean-square acceleration suppression exceeding 77% at monitoring points. These results demonstrate that the active control method effectively suppresses vibrations in beam-pointing-sensitive modes.

The establishment of an equivalent model of liquid sloshing in spacecraft tanks is of great importance for the stabilization of spacecraft attitude motions and the design of attitude control system. In this paper, a composite moving pulsating ball equivalent mechanical model (MPBM) with parameter identification and neural-network based error correction is proposed. In this model, the MPBM parameters are identified using a genetic algorithm combined with a particle swarm optimization algorithm (GA-PSO). The associated model error is predicted using a gate recurrent unit (GRU) neural network and compensated. Numerical experiments have been conducted and simulation results have confirmed the accuracy and reliability of the composite model, as well as the fast estimation of sloshing force and moment compared with the original MPBM.

In order to track multiple maneuvering extended targets accurately, an adaptive interacting multiple model algorithm based on variational inference (AIMM-VI) is proposed. An augmented state is constructed to cater for time-varying orientation angle and track realistic shape changes, resulting in better elliptical shape estimation and tracking accuracy. Multiple measurements from multiple extended targets are effectively assigned to corresponding targets through the marginal association probability distribution criterion, and the variational inference is used to accurately estimate the augmented state and shape information, which greatly improves the parameters estimation performance. The residual and likelihood functions are updated in real-time according to the results of variational inference, allowing for the updating of the model probability in real-time. The Markov probability transfer matrix is subsequently adaptively updated by the compression ratio, which makes the algorithm more adaptable to maneuvering target and significantly improves the adaptability and robustness of the algorithm. The final simulation and experiment results show that the proposed algorithm can effectively improve the tracking performance of multiple maneuvering extended targets.

High reliability and intelligence mark the cutting-edge development trend of high-speed vehicle control technology. This research focuses on the progress of high-speed vehicle control technology based on reinforcement learning, and sorts out its application in control parameter tuning, compensation control, and end-to-end control. Focusing on the development framework of intelligent control safety and efficiency, this paper deeply analyzes the challenges of safety, training efficiency, and interpretability faced by high-speed vehicle in reinforcement learning control, and proposes feasible paths and development directions for future research.

The propulsion system failure is statistically acknowledged as the most fatal factor of launch vehicles, which has received extensive attention. In this paper, mission re-planning is conducted to address typical thrust faults when they exceed the adaptability of the guidance system. This is achieved by generating degraded orbits according to the residual capacity of the launch vehicle using successive convex optimization. Since the uncertainties of some critical parameters provided by the fault diagnosis system are not considered in the re-planning process, their influence is then analyzed by the polynomial chaos expansion (PCE) method. Considering the non-coincident engine cut-off phenomenon, an additional coasting phase is introduced to enable the evaluation of the stochastic distribution of the final orbit by PCE. Moreover, a deep neural network (DNN) is trained to reduce the time consumption of the uncertainty evaluation process. By implementing the DNN, the terminal states can be predicted directly from the fault information, enabling the online application. Simulation results verify the effectiveness and the accuracy of the PCE-based uncertainty evaluation. Besides, the DNN-assisted PCE is confirmed to greatly improve the computational efficiency while maintaining comparable accuracy to Monte-Carlo simulation and conventional PCE. Since the computational time of the DNN-assisted PCE is on the order of hundreds of milliseconds, it can be applied in real-time to support making appropriate and reliable mission re-planning decisions based on probability.

The LS-DYNA simulation software was used to study the overload characteristics of a projectile penetrating a layered protective structure at high velocity. Firstly, the simulation data were compared with experimental data to verify the accuracy of the finite element model. The process of projectiles penetrating two different protective structures was analyzed, and the overload characteristics of the projectile under different working conditions were studied. Results show that the peak overload of the projectile penetrating the light protective structure at 1200 m/s and 1700 m/s can exceed 80,000 g and 130,000 g, respectively, and the peak overload of the projectile penetrating the heavy protective structure at 1200 m/s and 1700 m/s can exceed 40,000 g and 70,000 g, respectively. When the projectile penetrates a lightweight protective structure with different material shielding layers at the same velocity, the overload peak value of penetrating the shielding layer material of reinforced concrete is greater than that of penetrating the shielding layer material of granite. The deceleration peak value of the projectile penetrating a light protective structure is larger than that of a projectile penetrating a heavy protective structure at the same velocity mainly due to the good buffering effect of the thick soil layer of the heavy protective structure.

Liquid rocket engines are fault-prone parts on launch vehicles. Due to its complex working environment and strict performance requirements, liquid rocket engines often face many kinds of failure risks during actual commissioning and operation. In view of the high risk of liquid rocket engine failure and the scarcity of abnormal video data in the actual commissioning process, the traditional fault monitoring methods are faced with many challenges. In response, this paper proposes a fault simulation testing methodology specifically for liquid rocket engines under complex interference conditions. A semi-physical model has been developed to mimic the abnormal states that liquid rocket engines may experience during debugging or operational activities. This model enables the collection and generation of a series of video data that closely resemble real-life fault scenarios, enhancing the effectiveness of fault monitoring and analysis. Finally, by comparing with the data of the actual test run, the simulation test data achieved a high degree of similarity, indicating that the designed simulation test can effectively simulate the actual physical process during the actual test run. Through the innovative fault simulation test method, this study successfully solved the problem of abnormal video data scarcity, and provided support for the research of liquid rocket engine video anomaly monitoring.

Surveillance and anti-surveillance are currently the dominant forms of orbital game of spacecraft. Based on the maneuver capabilities and surveil strategies of typical surveillance satellites, an evasion strategy as well as a defend strategy using an escort satellite are proposed. The maneuver capabilities of a typical geostationary earth orbit (GEO) satellite are first demonstrated, followed by a detailed demonstration of the evasion abilities against the approaching surveillance satellite. Then a high-maneuvering escort satellite is proposed as another way to cope with the surveillance satellite and the corresponding defend strategies are analyzed. Simulation results demonstrate that a normal satellite can hardly escape the approach and detection of a smart surveillance satellite. However, a high-maneuvering escort satellite can maintain precise sight tracking of the surveillance satellite, which means with certain protective payloads installed, the escort satellite can successfully drive the surveillance satellite away from our high-valued GEO satellite.

A fixed-time orbital rendezvous guidance strategy was proposed to meet the requirements of the time-sensitive pursuit-capture game mission. A key problem of fixed-time orbit rendezvous is the design of deceleration guidance strategy and the choice of transfer time. In order to solve the deceleration guidance problem under limited thrust, a displacement formula under constant rocket thrust is proposed. Basing on the formula, a deceleration guidance strategy of "pulse correction, deceleration condition, inverse-relative-velocity deceleration" was designed so that the spacecraft can meet the terminal position constraint. Basing on the formula, a deceleration guidance strategy of "pulse correction, deceleration condition, inverse-relative-velocity deceleration" was designed so that the spacecraft can meet the terminal position constraint. For the mission time delay caused by deceleration process, a differential correction method was designed based on the displacement formula, which can obtain the Lambert transfer time corresponding to a given mission time. With the proposed method, the mission time error is reduced less than 1 s.