KEYWORDS: Object detection, Convolution, Defect detection, Detection and tracking algorithms, Target detection, Small targets, Transformers, Matrices, Commercial off the shelf technology, Algorithm development
Given the low detection accuracy, slow speed, and impoverished comprehensiveness of existing Printed Circuit Board (PCB) surface defect detection in small target detection, a lightweight YOLOv7 improved algorithm is proposed. First, the ordinary convolution operation is replaced by Ghost, the model parameters are significantly reduced, the accuracy is almost no loss, and then the Convolutional Block Attention Module (CBAM) is added. Finally, the Contextual Transformer module is added to the detection header to increase the model’s focus on defect features, which can combine contextual feature information to improve the representation of small target features. Ablation experiments were performed on the PCB datasets provided by the Intelligent Robot Open Laboratory of Peking University, combined with the datasets of 10,000 different PCB defect images collected by ourselves. The experimental results showed that the enhanced model reduced the number of parameters by 54% compared with the previous model, and the detection precision mAP was 97.02%. The running speed is 53.4 FPS, which suits the need for high detection precision and speed in industrial.
This article proposes a variable-leakage-flux flux-intensifying permanent magnet machine (VLF-FIPMM). Through the addition of magnetic bridge and the innovative design of magnetic barrier, the machine owns the feature of Ld<Lq and variable-leakage-flux characteristic, which not only widens the speed, but also reduces the irreversible demagnetization risk and core loss. Firstly, the design idea and operating theory of the VLF-FIPMM are analyzed. At the same time, a multi-objective genetic algorithm based on sensitivity analysis is introduced to obtain the optimal torque, torque ripple and reverse saliency ratio. Then the overall performance of the VLF-FIPMM is compared with the conventional IPM machine. Finally, the stress and deformation of the VLF-FIPMM are simulated at high speed. The above simulation results also validate the reliability of the design method and optimization.
In this paper, two new variable leakage flux permanent magnet motors with different structures are proposed. The leakage flux of the two motors can be adjusted automatically with the change of q-axis current, and the operation principle of the two motors is analyzed by using equivalent magnetic circuit analysis model. Furthermore, the two motors owe the characteristic of Ld<Lq through the special design of rotor structures to enhance the flux-weakening capacity. The finite element method is used to analyze the electromagnetic characteristics, temperature characteristics and mechanical characteristics of the two motors in detail. The results verify the characteristics of Ld<Lq and the controllable leakage flux of the two motors, and also verify that the motor with multi-stage permanent magnets has a wider speed regulation range, a larger output torque, lower temperature rise and better robustness than the motor with single-stage permanent magnets.
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