Qiongying Lv

The fault of one of the key systems in artificial satellites, the Control Moment Gyroscope (CMG), can lead to significant economic losses and irreparable consequences. Therefore, it is crucial to diagnose its faults promptly. Traditional fault diagnosis methods, however, face challenges such as local feature traps and difficulty in feature extraction when dealing with CMG vibration signals, making it hard to meet the requirements for accuracy and robustness. Hence, it is essential to design a high-accuracy model to assess the health status of CMG on time. To address these issues, a fault diagnosis method that combines the Joint Attention Mechanism (JAM) with one-dimensional dilated convolutional networks and residual connections is proposed. The method efficiently learns feature information through the JAM, effectively addressing the time-varying characteristics of vibration signals and focusing more on fault-related features. The influence of rotational speed on the model is overcome to some extent through JAM. The three rotational speeds are mixed as datasets, and the model achieves high accuracy. The proposed method significantly enhances the accuracy and robustness of CMG fault diagnosis. Experimental results on a self-collected dataset demonstrate that the proposed method achieves excellent accuracy (98.14%) and robustness in CMG fault diagnosis.

In laser tracking systems, capturing moving targets is a prerequisite to guaranteeing a tracking system’s performance. Previous studies have confirmed that the capture probability of hexagonal spiral scanning is higher than that for other scanning methods, but there is still room for improvement. This article proposes an improved hexagonal honeycomb scanning capture method based on hexagonal spiral scanning for a prior moving target model with a Gaussian distribution positioned within the scanning range of the visual threshold. Through experimental verification, it was found that, within the same scanning field of view, the capture probability can be increased by 3% compared to that in traditional hexagonal spiral scanning, making the capture probability greater than 98%. The improved hexagonal honeycomb structure scanning method proposed in this article provides a new solution for target acquisition problems in fields such as laser communication, laser docking, and airborne radar.

Free-form surfaces have good aberration correction capability and balance capability for nonrotationally symmetric imaging systems. In this study, we analyzed the quantitative relationship between X–Y polynomial combination and aberration for the efficient design of X–Y free-form optical systems. The purpose of this study was to provide an exhaustive design method for off-axis triple inverse optical systems with X–Y free-form surfaces. Finally, we designed a free-form off-axis optical system with a large field of view (FOV) and low distortion based on the off-axis triple inverse optical system without an intermediate image plane. The primary mirror (PM) of the system adopted an X–Y polynomial free-form surface to correct the aberration of different FOVs of the system and improve the image width and quality. The optical system had a focal length of 1000 mm, an F-value of 9.5, an FOV angle of 23° × 1°, a maximum distortion grid in the FOV less than or equal to −0.05%, and a full-field average wave aberration better than 0.055 λ (λ/18.2, λ = 632.8 nm). The analysis of the design results showed that the system had high-quality imaging and a compact structure. This design method can provide a technical reference for the study of such free-form off-axis systems.

Ducted fans with thin‐shelled tubular structures are typically used in unmanned aerial vehicles. However, due to their thinness and heterogeneity, the ducts are prone to warpage deformation, which can adversely affect the aerodynamic characteristics of the fans. In this study, Moldflow software was used to analyze and reduce the warpage deformation of a duct made of 15 wt% glass fiber‐reinforced acrylonitrile butadiene styrene. First, a Taguchi experiment was performed to determine the main factors affecting the warpage: the mold surface temperature, melt temperature, injection pressure, and holding pressure. Subsequently, the response surface methodology (RSM) was employed to define a regression equation and response surface relating the dependent and independent variables, and a genetic algorithm (GA) was used for optimization. The maximum warpage was successfully reduced from 0.2217 to 0.0465 and 0.0578 mm through the RSM and GA analyzes, respectively, and the simulated results were validated by data collected using a COMET L3D system. Finally, the influence of the warpage of the ducted rear deflector on the aerodynamic performance was investigated by performing computational fluid dynamics analysis. The results indicated that curving the rear deflector has a beneficial effect on aerodynamic performance, as it increases velocity, but it also reduces the impact of the torque balance. This paper describes an innovative application method using a specific combination of analysis tools to address the problem of optimizing the design, modeling, and performance of ducted fans. This work can help predict manufacturing results and aerodynamic effectiveness at an early stage.

The rationality of the structure design of the Laval nozzle directly affects its work efficiency. The simulation software is used to simulate and analyze the structure and operating conditions of the Laval nozzle, and to find the relationship between the change of the turbulent boundary layer jet flow pattern. From the simulation results, it can be seen that the outlet diameter under a single variable cannot directly determine the value and range of the jet Mach number, but it produces a huge change in the mixing zone of the turbulent boundary layer, which directly affects the turbulent kinetic energy.

The design of the rectangular nozzle affects the thrust and stealth performance of the propeller. The relationship between the outlet area and the jet flow pattern is studied through the simulation analysis of three different outlet area rectangular nozzles with an aspect ratio of 8. From the simulation results, it can be seen that the exit area under a single variable determines the value and range of the jet Mach number, which produces a huge change in the mixing zone of the turbulent boundary layer, but it has nothing to do with the development trend of the near and far field.