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Aiming at the voltage fluctuation problem caused by indirectness and uncertainty in new energy power generation system, the backstepping control strategy is firstly applied in electric spring (ES) system, and an ES backstepping control strategy with command filtering is proposed. According to the mathematical model of ES, the controller is designed by backstepping method and command filter is added to solve the computational inflation problem in ES backstepping control. Meanwhile, the error compensation signal is designed, and the stability of the system is verified by the Lyapunov stability theory. The effect of ES on critical load (CL) voltage stabilization is simulated when the grid-side voltage of the new energy power generation system fluctuates, and the sensitivity analysis of different system parameters to the control strategy is discussed in this paper. Compared with traditional proportional integral (PI) control, the dynamic response speed of CL voltage is improved by 0.07 s, while the CL voltage distortion rate is reduced by 31%. In parameter sensitivity analysis, the maximum deviation rate of CL voltage is 0.318%. Meanwhile, the maximum voltage amplitude fluctuation range that it can withstand is increased by 52.9 V. It is verified that the control strategy proposed in this paper has the advantages of fast response, low harmonic content and strong anti-interference ability.

Aiming at the accurate speed tracking control of electric vehicles (EV) driven by permanent magnet synchronous motors (PMSM) under external load torque disturbances, this paper proposes an approach for prescribed performance back-stepping control based on a disturbance observer. Firstly, a controller was designed using the back-stepping technique, and a second-order sliding mode differentiator was introduced to approximate the derivative of the virtual control law, which can solve the "differential explosion" problem in traditional back-stepping control techniques. Secondly, in order to reduce the influence of motor load disturbances in the driving process of EV, a novel disturbance observer was proposed, bolstering the anti-interference capability of system. In addition, to achieve the preset high transient and steady-state speed tracking performance, a prescribed performance control strategy was incorporated to guarantee tracking errors within predefined boundaries. Finally, the Lyapunov function was utilized to verify the system stability. The simulation results showed that, compared with traditional PI control, the designed controller significantly increased motor speed tracking precision by more than 5 times, demonstrating a superior speed tracking performance and enhanced anti-interference capability.

The upper airway cough syndrome (UACS) is a common chronic cough in children, and it has gradually increased in recent years. Chinese medicine believes that the main location of the disease is nasopharynx, which is closely related to the spleen and kidney. The most common pathological factor is wind, phlegm, deficiency and stasis, and the basic pathogenesis is upward inversion of lung Qi. Chinese medicine treatment mainly focuses on the combination of disease and syndrome differentiation, the combination of body and syndrome differentiation, staged Chinese medicine differentiation and treatment, cold and heat syndrome differentiation, viscera syndrome differentiation, Chinese medicine external treatment and combination of Chinese medicine and western medicine in order to regulate lung Qi. This article mainly elaborates on the differentiation and treatment of Chinese medicine for pediatric UACS, as well as its clinical treatment effects to provide some reference for further research on the treatment of pediatric UACS with Chinese medicine.

[Objective] Vehicle detection is critical for urban intelligent transportation. Focusing on small target problems, high-density problems, and motion attribute problems, this study takes traffic surveillance images as input and aims to detect moving vehicles. [Method] Based on the anchor-free CenteNet, a detection method of multi-scale features and dual-source motion perception was proposed. Firstly, coordinate attention was introduced to the multi-scale and global context features of the network's abstraction layer, so as to supplement information in multiple stages and at multiple levels and improve the model's understanding of vehicles and scenes. Secondly, through fuzzy textures representing actual motion features of vehicles and optical flow knowledge representing general motion features of vehicles, the model's perception ability of moving vehicles was constructed. [Result] The experimental data came from the public dataset UA-DETRAC. The mean average precision (mAP) and frames per second (FPS) were used as the evaluation metrics of accuracy and speed. Experiment results show that the mAP and FPS of the proposed method are 70% and 30 frame/s respectively, which have the best balance between speed and accuracy among other compared methods. [Conclusion] It maintains that the proposed method is competent in the task of moving vehicle detection. [ABSTRACT FROM AUTHOR]

Salix sand barriers have been widely used in arid and semi‐arid regions of northern China as an environmentally friendly approach to control wind erosion. However, the inherent variability in length and thickness of Salix branches complicates achieving the desired fence porosity, typically resulting in an error of approximately 10% or more. This defect affects the fence's wind protection, thereby limiting their broader application. To address these challenges, we conducted a field experiment in the Hobq Desert, where we established Salix fences with porosities of 23%, 37%, and 44%, and measured the airflow velocities around these fences. The results indicated that the fence with 37% porosity exhibited the most effective sheltering effect, providing a protection distance up to 7.14 times of the fence height. A total of 44% porosity fences are also reasonably effective for practical purposes. On the other end of the spectrum, fences with 23% porosity demonstrated a better sediment interception than its high porosity peers, achieving an interception rate of 81.46%. Therefore, we conclude that organic fences made from Salix branches can serve as efficient windbreaks. Our findings provide foundational data for the application of organic fences in arid and semi‐arid regions of northern China, and potentially similar environments globally. [ABSTRACT FROM AUTHOR]

Current research on engine transient performance primarily focuses on the variation of key aerothermodynamic parameters in specific sections, neglecting the comprehensive understanding of the engine's inner flow field during transient operations. To address this gap, this paper proposes a two-dimensional transient simulation method that effectively captures the evolution of the flow field in the meridional plane. The approach involves deriving circumferential averaging equations in a rotating coordinate system with variable angular velocity, considering angular acceleration source terms. The engine components, including the compressor, combustion chamber, turbine, and rotating shaft, are individually modeled. The newly derived governing equations are solved using a dual-time-step approach, where an inner-iteration ensures mass flow conservation, and an outer-iteration updates the rotational speed. Using a real turbojet engine as a case study, transient examinations comprising acceleration and deceleration are performed. A comparative analysis of experimental and simulation results is conducted, revealing an average error of 0.9% in shaft speed, 7.8% in engine thrust, 1.7% in engine exhaust temperature, and 5.1% in compressor outlet pressure. Additionally, the study analyzes and compares the internal flow fields during the transient process, contributing to a deeper understanding of the engine's dynamic behavior. The research effort establishes a practical methodology and technology for conducting comprehensive two-dimensional engine transient cycle analyses within reasonable computational resources and timeframes. [ABSTRACT FROM AUTHOR]

An integral sliding mode observer-based fixed-time multi-faults estimation method is proposed to solve the problem of fast fault estimation for a class of nonlinear systems with multiple types of faults simultaneously. First, a class of nonlinear systems with actuator and sensor faults is considered, and the original system is transformed into two subsystems through coordinate transformation to decouple the actuator and sensor faults. Then, intermediate variables are introduced to transform sensor faults into actuator faults of the augmented systems. For the transformed system, a fixed-time fault observer based on integral sliding mode is designed to realize the fast estimation of unknown terms, and the fixed-time convergence performance is proved. Moreover, based on the output of the fault observer, the actuator and sensor faults in the original system are reconstructed. Finally, the fault model of the permanent magnet synchronous motor is established in the hardware-in-the-loop platform, and the effectiveness of the designed fault estimation method is verified. [ABSTRACT FROM AUTHOR]