This paper investigates delay-dependent stability analysis and stabilization for continuous Takagi-Sugeno fuzzy systems with a time-varying delay. By employing dynamic delay partition, the delay interval [0, d(t)] is partitioned into some variable subintervals so that much more information of time-varying delay can be utilized. Moreover, a novel relaxed integral inequality is applied to estimate the derivative of LKFs for achieving reduction of estimation gap. As a result, several further robust stability and stabilization criteria with less conservativeness are proposed. Finally, three examples are provided to demonstrate the effectiveness and advantages of the presented methods.

Becausethe fluctuation and uncertainty of wind power generation bring severe secure and economic challenges to power systems, wind power forecasting becomes the critical part of the management in power systems. In this paper, a hybrid approach based on unequal span segmentation-clustering is proposed to mine the variation trend information in the wind speed series for improving forecasting performance. Firstly, the wind speed series representation is proposed to accurately represent the major variation trend of the wind speed series. It reduces the influence of the non-stationary and irregular behaviors of the wind speed series on the unequal span segmentation-clustering. Secondly, the shape-position comprehensive evaluation is proposed to combine shape and position measures to evaluate the clustering of the trend segments with unequal length. It identifies the trend segments which have comprehensive similarity on both shape and position to better construct forecasting models. Thirdly, novel bayesian optimization mutation operators are proposed to optimally move or add cut points in the unequal span segmentation. It enhances the local search capability of the unequal span segmentation. By comparing different approaches using wind datasets from two wind farms, the effectiveness and advantages of the proposed approach are demonstrated.

In the production and service of pipelines, automated electromagnetic detection is widely employed to diagnose potential defects. However, the single inspection method can hardly meet reliability and multi-position detect detection simultaneously due to limited signal features. In this paper, a novel composite approach of electromagnetic acoustic transducer and eddy current is proposed to detect different kinds of defects combining their technical merits. A comprehensive theoretical analysis of the composite approach is given to derive the modified model of the send-receive mode. The influences of the critical parameters on hybrid signals are discussed and the probe performance is improved over 65% in magnitude. Then, the time-division multiplexing strategy is utilized to separate hybrid signals. Finally, laboratory experiments are conducted to extract independent features and diagnose potential defects in the steel plate. Results indicated that the proposed approach could achieve a good performance in the detection task of inner and outer defects. Compared with existing detection methods, our proposed approach has significant merits in detectability and efficiency.

The detection of surface and backside defects in steel plates is essential for safety maintenance. Current ac magnetic flux leakage (ACMFL) testing systems generally operate at a high frequency but cannot detect backside defects owing to the skin effect. Low-frequency ACMFL is limited by low sensitivity and low efficiency in detecting deep defects. This letter presents a multifrequency ACMFL testing method combined with the merits of low- and high-frequency excitation to detect surface and backside defects. In early work, the optimal frequency for detecting the surface defect with a depth of 4 mm or less was 400 Hz. Through simulation analysis, the optimal low frequency for detecting backside defects is determined. Additionally, the influence of the excitation intensity on the response signal is investigated. Relatively small excitation power should be used to obtain a reliable detection waveform. Finally, the experimental results of surface and backside defects detection validated the practicality of the method.

This paper is concerned with the event-triggered practical fixed-time containment control for stochastic multi-agent systems, in which the input delay is considered. A novel event-triggered mechanism is proposed, where the containment error of stochastic MASs is considered as a part of the threshold function in the form of an exponential decreasing function, which can provide more freedom to balance system performance and resource utilization. Then, a practical fixed-time containment control scheme is presented, whose convergence time is not affected by the initial conditions. Furthermore, Pade approximation technique is utilized to convert the input delay to the case without delay. The design process of the controller is simplified, and the computational complexity is reduced. Finally, two examples are rendered to demonstrate the performance of the presented method.

Rayleigh wave methods utilizing electromagnetic acoustic transducers (EMATs) are widely used to detect a crack defect on the metal surface due to the merits of high sensitivity and long detection distance. However, the current EMATs for Rayleigh wave has low energy conversion efficiency and usually produce a wide echo-wave packet, reducing the spatial resolution and signal-to-noise ratio of detection signals. To address the issues, the coil spatial pulse compression technique (CSPCT) is proposed to improve the physical structure of EMATs. First, a comprehensive analysis of the coil design is given to realize spatial phase encoding pulse compression. Second, the influence of the key parameters of EMATs on the pulse compression effect is studied. Finally, the crack detection experiment is conducted on an aluminum plate to verify the performance improvement of the designed EMAT. Compared to existing EMATs, our designed EMATs reduce the width of the main lobes and enhance the amplitude of the echo-wave signals. Results indicated that the spatial resolution was improved by up to 72% with an increase of 0.72 dB in signal-to-noise ratio. In comparison to the existing time-domain pulse compression technique, the CSPCT requires no complex hardware and software tools, which has the merits of low cost and fast response. This work expands the application boundary of EMAT systems.