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To match the key features of light-emitting diode (LED) lighting source and further save power, LED lighting driver also requires long life, while maintaining high efficiency, high power factor, pulse-width modulation dimming and low cost. However, a typical LED lighting driver has the following drawbacks: (i) utilise bulky electrolytic capacitor as storage capacitor with short lifetime; (ii) employ a low-frequency diode bridge as the rectifier cell; and (iii) engage multiple stages cascade structure for multiple LED strings. To overcome the aforementioned shortages, this study proposed a bridgeless electrolytic capacitor-less AC/DC converter for offline LED lighting application. In the proposed converter, the conventional diode rectified bridge is replaced by Totem-pole bridgeless configuration for reducing the number of semiconductors in the line-current path. Meanwhile, the valley-fill circuit is introduced to further reduce the capacitor size. As comparison to its counterpart, the proposed circuit requires only one quarter of the capacitor energy when considering the energy amount (CV2) as the capacitor sizing criterion. Furthermore, the isolation type of the studied circuit is compatible with Twin-Bus configuration for achieving higher overall system efficiency. Finally, the experimental results, taken from a laboratory prototype rated at 50 W, are presented to verify the effectiveness of the proposed converter.

This paper investigates the problem of nonlinear path following control of underactuated marine vehicles in the horizontal plane. Firstly, appropriate kinematic and dynamic models are established, where the kinematic model is developed in terms of the relative velocity with respect to the ocean current disturbances, and the dynamic model is developed to include the effects of wind and wave disturbances. Based on the time delay control method and the reduced-order linear extended state observer (LESOs) technique, an improved compound line-of-sight (CLOS) guidance law is first proposed which can estimate the unknown sideslip angle and can compensate for the effects of time-varying ocean currents. Secondly, the control law is decomposed into the kinematic and dynamic controllers by the back-stepping technique. The high-order tracking differentiator is applied to construct derivatives of desired yaw angle, which are calculated by the CLOS guidance law. This approach resolves the problem of computational complexity inherent in the traditional back-stepping method and simplifies the overall controller. The lumped disturbances caused by waves and wind are estimated and compensated by the reduced-order LESOs. Finally, stability analysis of the closed-loop system is performed. The simulation results and comparative analysis validate the effectiveness and robustness of the proposed control approach.

This paper proposes a formation control method for two underactuated unmanned surface vessels (USVs) to follow curved paths in the presence of ocean currents. By uniting a line-of-sight (LOS) guidance law and the null-space-based behavioral control (NSB) framework, we achieve curved path following of the barycenter, while maintaining the desired vessel formation. The closed-loop dynamics are investigated using cascaded systems theory, and it is shown that the closed-loop system is USGES and UGAS, while the underactuated sway dynamics remain bounded. Simulations show that the barycenter task errors converge to zero, validating the theoretical results, while a small cross-track error is observed in the experiments.

In this study, we investigate heavy ion irradiation effects on commercial 650 V p-GaN normally-off HEMTs. Ge and Cl ions are used to irradiate the GaN devices in the experiments. Ge and Cl ion beam irradiation have little impact on the output characteristics of GaN devices. After heavy ion irradiation, the leakage currents between source and drain electrodes increase significantly under off-state, decreasing the breakdown voltage (BV DS ) sharply. Additionally, Ge and Cl ion irradiation have little effect on the trap states under the gate electrode; thus, the gate leakage currents increase slightly. Many line-shaped crystal defects extending from the surface to the GaN buffer layer can be captured using a transmission electron microscope after Ge/Cl ion irradiation. The buffer layers of the irradiated devices were damaged, and the leakage path was generated in the buffer layer. Defect percolation process in buffer layer is the dominant factor of irradiated high-voltage GaN device failure.

An adaptive line-of-sight (ALOS) guidance law with drift angle compensation is proposed to achieve the path following of unmanned surface vehicles (USVs) under the influence of ocean currents. The ALOS guidance law can calculate the desired heading of USV accurately. Compact Form Dynamic Linearization—Model-Free Adaptive Control (CFDL-MFAC) is used to control the heading. Firstly, the relationship between the path tracking error and the USV model is established. The look-ahead distance is designed as a function related to the tracking error and the speed. The sideslip angle is estimated online and compensated by using the reduced-order state observer. Finally, the heading is controlled using CFDL-MFAC, which is calculated by the ALOS guidance law. The simulation results demonstrate that satisfactory performance has been achieved of the ALOS by comparing the mean absolute error (MAE) and root mean square error (RMSE).

With the rapid rise of the Internet, China’s e-commerce has also flourished. The development of e-commerce has led to an increase in the volume of logistics and distribution. The further development of e-commerce has also placed higher demands on the timeliness of logistics and distribution. The competition of e-commerce companies has shifted from the competition between business models to the competition between logistics services. The scientific and rational distribution site selection planning is the prerequisite and guarantee for the efficient operation of logistics distribution network. To balance the contradiction between logistics distribution speed and distribution cost has become the key to competition among e-commerce companies. This paper analyzes the current network structure and distribution mode of e-commerce logistics city distribution, and analyzes and discusses the problems existing in current e-commerce logistics city distribution. Furthermore, the bi-level programming is studied. According to the characteristics of the bi-level programming problem, the genetic algorithm flow suitable for bi-level programming is proposed. The bi-level programming model of urban distribution service network site selection with limited lines is proposed. Through the verification of the genetic algorithm in this paper, the proposed method can plan a reasonable service site location layout and distribution models and path selection. The results show that the average daily fuel cost can be reduced by 37.6%, and the transportation distance and fuel cost can be optimized best.

In the marine environment, the motion characteristics of Autonomous Underwater Vehicles (AUVs) are influenced by unknown factors such as time-varying ocean currents, thereby amplifying the complexity involved in the design of path-following controllers. In this study, a backstepping sliding mode control method based on a current observer and nonlinear disturbance observer (NDO) has been developed, addressing the 3D path-following issue for AUVs operating in the ocean environment. Accounting for uncertainties like variable ocean currents, this research establishes the AUV’s kinematics and dynamics models and formulates the tracking error within the Frenet–Serret coordinate system. The kinematic controller is designed through the line-of-sight method and the backstepping method, and the dynamic controller is developed using the nonlinear disturbance observer and the integral sliding mode control method. Furthermore, an ocean current observer is developed for the real-time estimation of current velocities, thereby mitigating the effects of ocean currents on navigational performance. Theoretical analysis confirms the system’s asymptotic stability, while numerical simulation attests to the proposed method’s efficacy and robustness in 3D path following.

In order to address the irregularity of the welding path in aluminum alloy frame joints, this study conducted a numerical simulation of free-path welding. It focuses on the application of the TIG (tungsten inert gas) welding process in aluminum alloy welding, specifically at the intersecting line nodes of welded bicycle frames. The welding simulation was performed on a 6061-T6 aluminum alloy frame. Using a custom heat source subroutine written in Fortran language and integrated into the ABAQUS environment, a detailed numerical simulation study was conducted. The distribution of key fields during the welding process, such as temperature, equivalent stress, and post-weld deformation, were carefully analyzed. Building upon this analysis, the thin-walled TIG welding process was optimized using the response surface method, resulting in the identification of the best welding parameters: a welding current of 240 A, a welding voltage of 20 V, and a welding speed of 11 mm/s. These optimal parameters were successfully implemented in actual welding production, yielding excellent welding results in terms of forming quality. Through experimentation, it was confirmed that the welded parts were completely formed under the optimized process parameters and met the required product standards. Consequently, this research provides valuable theoretical and technical guidance for aluminum alloy bicycle frame welding.

Path tracking has a significant impact on the success of long-term autonomous underwater vehicle (AUV) missions in terms of safety, energy-saving, and efficiency. However, it is a challenging problem due to the model uncertainty, and ocean current disturbance. Moreover, the widely used line of sight (LOS) algorithm with fixed lookahead distance does not perform well because it requires an urgent need for the automatic adjustment of the parameter. Considering the above, this study proposes an adaptive line-of-sight (ALOS) guidance method with reinforcement learning (RL) based on the dynamic data-driven AUV model (DDDAM). Firstly, we introduced a detailed AUV dynamic model mainly including the models with and without current influence. Next, we conducted a detailed analysis of the path tracking error dynamics and the factors influencing the tracking performance based on the model proposed above. We then used the DDDAM (using long short-term memory (LSTM) neural network) to pre-train the RL framework to generate more samples for online learning in order to speed up the learning process. Finally, the deterministic policy gradient (DPG) based RL was designed to optimize the continuously varying lookahead distance considering the previously analyzed factors. Collectively, this paper presents simulation cases and an evaluation of the algorithm. Our results indicate that the proposed method significantly improves the performance of path tracking with effectiveness and robustness.

Based on a line-of-sight (LOS) guidance law for a curve parametrized path, a finite-time backstepping control is proposed for the kinematic path-following of an underactuated autonomous surface vehicle (ASV). Finite-time observer is utilized to estimate the unknown external disturbances accurately. The first-order Levant differentiator is introduced into the finite-time filter technique, such that the output of filter can not only approximate the derivative of the virtual control, but also avoid the singularity problem of real heading control. The integral terminal sliding mode is employed to improve the tracking performance and converging rate in the surging velocity control. By virtue of Lyapunov function, all the signals in the closed-loop system can be guaranteed uniformly ultimate boundedness, and accurate path-following task can be fulfilled in finite time. The simulation results and comparative analysis validate the effectiveness and robustness of the proposed control approach.