查看更多>>摘要：In this paper, a fault detection scheme for a tank system using support vector machine (SVM) combined with ChangeFinder, which are both machine learning methods, is studied. SVM can detect faults on a nonlinear system, but it can be late because SVM cannot recognise the nature of the time series. Combination with ChangeFinder enables SVM to recognise the nature of time series, and early detection using SVM becomes possible. Simulations and experiments assuming the temperature sensor fault case for the temperature control system of the tank system have been done and 5 s reduction of detection time was confirmed. In addition to the situation of the tank system, the sine wave input showed the effectiveness of the proposed method for general input. In addition, the superiority of the proposed method over ChangeFinder in an experimental environment was confirmed.
查看更多>>摘要：Aiming at the problems of difficulty and low detection accuracy in manual detection of scratches on the inner surface of ultra-long energy storage gas cylinders in the aerospace industry, a detection system for scratches on the inner surface of ultra-long gas cylinders based on VGG-16 neural network is designed. In this paper, VGG-16 recognition model is innovatively proposed to apply to the application of scratch detection. Compared with the ordinary detection model to detect the required target from the complex background, this article first processes the image acquired by the image acquisition module into a single binary image with a scratched area and a non-scratched area. The VGG-16 recognition model learns the characteristics of the scratches, so as to recognise the scratches under the ordinary background, and achieve the purpose of scratch detection. The results show that the accuracy rate of the scratch detection on the inner surface of gas cylinders reaches 98.5%, which greatly improves the accuracy rate of the scratch detection compared with the previous manual detection methods.
查看更多>>摘要：In wireless power transfer systems, the enhancement of dynamic response may result in inferior steady-state response. To deal with the contradictions, the weighting function in the robust control design systems should be chosen carefully. So the selection of designed parameters would become a complicated and practically time-consuming problem. In this paper, a multi-objective optimisation scheme for operator-based robust nonlinear control of wireless power transfer systems is proposed by using modified ant colony optimisation algorithm to determine the values of designed parameters. First, the evaluation function to estimate system performance is formulated to guarantee its robustness and tracking performance. Then modified ant colony optimisation (MACO) algorithm is applied to search optimal values for designed parameters. Finally, the simulations results are presented to show good dynamic and steady response of the WPT systems even when the uncertain term exists.
查看更多>>摘要：It is difficult to measure the characteristics of human limbs during movement, which leads to the complexity and inaccuracy of solving the mechanical properties of the joints. However, these unknown variables are essential for designing exoskeleton robots and cannot be ignored. Therefore, a rod model of the lower limb is identified in this paper, the different stages of human gait are discussed, and the interaction between the feet and the ground during human walking is analysed in detail. On this basis, the joint moment of lower limbs is deduced. Furthermore, inverse dynamic, net joint force, and moments for human lower limb joints are analysed theoretically. Finally, the principle of the high-fidelity Hill model is investigated, which verifies the feasibility and effectiveness of solving the net force and moment for human lower limb joints based on the plantar reaction force under certain circumstances theoretically. The research results of this paper will contribute to the field of lower limb exoskeleton robots and human lower limb prostheses.
查看更多>>摘要：Aiming at the selection of inverter switching frequency and the harmonic problem of the dead time in reality, an optimal method for switching frequency of three-phase four-wire inverters considering the dead time to reduce the total harmonic distortion (THD) was proposed. Firstly, the output sinusoidal pulse width modulation (SPWM) wave was analysed by using double Fourier transform and Bessel function, and the spectrum of SPWM with dead time was obtained. Secondly, the relationship between the THD of the output voltage and the switching frequency was analysed. The study found that there is an optimal switching frequency to minimise the output voltage THD. Thirdly, the linear Lagrangian interpolation method was used to fit the formula for selecting the optimal switching frequency with different dead time. Finally, a three-phase four-wire inverter test prototype based on the TMS320F28335 control chip was built, and the effectiveness of the proposed method was verified through experiments.
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