Fuzzy Classification and Implementation Methods for Tugboat Main Engine Fault

The establishment of classification index system of fault in tugboat main engine was briefly discussed first. After that, the fuzzy method and procedures used in fault classification were introduced. Several implementation techniques of the fuzzy classification were explored including the knowledge expression, the hierarchical structure of knowledge library, the pre-processor and the forward inference engine. Some specific fault records of tugboat main engine were analyzed and classified for certification. And results prove that fuzzy classification has certain reference value and improves the working efficiency of tugboat personnel in equipment maintenance and management

A diode-MMC AC/DC hub for connecting offshore wind farm and offshore production platform

A diode rectifier-modular multilevel converter AC/DC hub (DR-MMC Hub) is proposed to integrate offshore wind power to the onshore DC network and offshore production platforms (e.g., oil/gas and hydrogen production plants) with different DC voltage levels. The DR and MMCs are connected in parallel at the offshore AC collection network to integrate offshore wind power, and in series at the DC terminals of the offshore production platform and the onshore DC network. Compared with conventional parallel-connected DR-MMC HVDC systems, the proposed DR-MMC hub reduces the required MMC converter rating, leading to lower investment cost and power loss. System control of the DR-MMC AC/DC hub is designed based on the operation requirements of the offshore production platform, considering different control modes (power control or DC voltage control). System behaviors and requirements during AC and DC faults are investigated, and hybrid MMCs with half-bridge and full-bridge sub-modules (HBSMs and FBSMs) are used for safe operation during DC faults. Simulation results based on PSCAD/EMTDC validate the operation of the DR-MMC hub

Research of the single‐rotor UAV gimbal vibration test

Abstract An experimental study was conducted to investigate the phenomenon of UAV attitude instability caused by large vibrations affecting single‐rotor UAV airborne equipment. Appropriate measurement points were selected to collect vibration signals from the unmanned aerial platform during takeoff and flight of the drone. The time‐domain response and power spectral density of the unmanned aerial platform were then obtained. Establish a dynamic model of the vibration reduction system for an unmanned aerial platform and design a two‐stage vibration reduction structure for the unmanned aerial platform. Through field flight tests of unmanned aerial vehicles, it has been demonstrated that the maximum time domain response of the platform after vibration reduction is 8.75 g (less than 50 g), and the maximum root mean square value of the power spectral density (PSD) is 1.82 g (less than 3 g). The designed secondary vibration reduction structure can serve as a reference for the design of vibration reduction in unmanned aerial vehicles

Research on Tool Remaining Life Prediction Method Based on CNN-LSTM-PSO

Efficient and accurate prediction of tool Remaining Useful Life (RUL) is the key to improve product accuracy, improve work efficiency and reduce machining costs. Aiming at the problems of weak tool wear state features, difficult extraction, and low prediction precision and accuracy, this research proposes a CNN-LSTM-PSO tool remaining life prediction method based on multi-channel feature fusion. Firstly, based on computer vision, feature extraction, information fusion technology, the multi-source sensor signals collected during the tool life cycle are effectively processed and analyzed, and a sample data set of spatio-temporal correlation of traffic flow is constructed. Secondly, the sample data set was input into the CNN-LSTM-PSO model, the CNN network obtained the sequence feature vector by extracting the spatial characteristics of traffic flow data, and the feature vector was input into the multi-layer LSTM network to extract the time-dependent features, and the PSO algorithm optimized the hyperparameters in the CNN-LSTM model. The accuracy of tool RUL prediction model and the efficiency of model fitting are further improved. The results show that the CNN-LSTM-PSO model can effectively predict tool wear, with the mean absolute error (MAE) value of 1.0892, the root mean square error (RMSE) value of 1.3520, and the determination coefficient $R^{2}$ value of 0.9961; Through the comparative analysis of ablation experiments, it is found that the method proposed in the research has the highest efficiency in fitting the tool RUL prediction model, the lowest values of MAE value and root mean square error RMSE, and the value of determination coefficient $R^{2}$ is closest to 1, which has certain advantages.The proposed method has reference value and engineering practical significance for the related research of tool wear residual life prediction

High Voltage Ride through Control of PMSG-Based Wind Turbine Generation System Using Supercapacitor

Regarding PMSG-based wind turbine generation system, this paper proposes a supercapacitor energy storage unit (SCESU) which is connected in parallel with the DC-link of the back-to-back converter to enhance its high voltage ride through performance. The analysis of the operation and control for the grid-side converter and SCESU are conducted. Based on real time digital simulators (RTDS), a model and a Hardware-in-the-Loop (HiL) platform of PMSG-based wind turbine with SCESU is developed, and the simulation results show that the SCESU absorbs the imbalanced energy and the grid-side converter absorbs inductive reactive power during the period of voltage swell and verify the correctness and feasibility of the high voltage ride through control strategy

Key Role of Left Atrial Appendage during Redo Ablation in a Case of Long-Standing Persistent Atrial Fibrillation

Extrapulmonary vein focal sources have been recognized as the source of atrial fibrillation in some cases, and empiric electric isolation of the left atrial appendage has been proposed for long-standing persistent atrial fibrillation by some. Here, we present a case of redo ablation of long-standing persistent atrial fibrillation in which the left atrial appendage played a key role in maintaining AF during ablation, and atrial fibrillation was terminated by electrical isolation of the LAA. During the ablation, a rare phenomenon of half of the atria in atrial fibrillation while the other half of the atria in atrial flutter was seen