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Zhang J.,Nanjing University of Science and Technology | Bo Y.-M.,Nanjing University of Science and Technology | Lv M.,North Information Control Group Co. | Ling M.-R.,Chongqing Wangjiang Industry Co. | And 2 more authors.
Nanjing Li Gong Daxue Xuebao/Journal of Nanjing University of Science and Technology | Year: 2012

In order to ensure the reliability of wireless networked control systems, a fault observer based on discrete switched systems is designed focusing on networked control systems composed of wireless sensor networks. The wireless networked control system is assumed to be fault and detected. The augmented fault observer is constructed by studying the transmission characteristics of the data of wireless sensor networks. The observer is equivalent to a discrete switched system. The stability condition of the observer is translated into a linear matrix inequality based on the Lyapunov stability theory, and the stability of the system is proved. The observer can keep track of the state of the original system in one second. When a fault occurs, the observer residue can change rapidly to detect the fault. The simulation example demonstrates the effectiveness of the proposed method. Source

Xia S.,Harbin Engineering University | Xu X.,Harbin Engineering University | Xu C.,Harbin Engineering University | Wang H.,Tianjin Port Free Trade Zone | And 2 more authors.
Environmental Technology (United Kingdom) | Year: 2015

Phosphate removal is an important method for controlling eutrophication in bodies of water. Adsorption is an effective phosphate removal approach. In this research, the adsorbent, namely, MnFe2O4, was prepared through the improved co-precipitation method and investigated in terms of phosphate removal. MnFe2O4 was characterized by scanning electron microscopy, vibrating sample magnetometry, X-ray diffraction, and Fourier transform infrared spectroscopy. Phosphate adsorption by MnFe2O4, desorption of adsorbed MnFe2O4 with the regeneration of desorbed MnFe2O4, and phosphate recovery were researched. Experimental results showed that adding the appropriate amount of polyethylene glycol to MnFe2O4 precursors during preparation inhibited the agglomeration of MnFe2O4 between particles because of the magnetic property of MnFe2O4 etc. High crystallinity and strong magnetism were achieved by MnFe2O4 at low temperatures. Average particle size was 5.1 nm. The hysteresis loops confirmed the ferrimagnetic behaviour of MnFe2O4 with a high saturation magnetization (i.e. 26.27 emu/g). The adsorption mechanism of phosphate was mainly physical. The prepared MnFe2O4 had a spinel structure. The proposed technique achieved a phosphate removal rate of 96.06%. A considerable amount of phosphate was desorbed from the adsorbed MnFe2O4 in 15 w/v% NaOH solution. The adsorption capacity of the desorbed MnFe2O4 could be restored to 96.73% in 10 w/v% NaNO3 solution through ion exchange. A sustainable phosphate source was recovered via hydroxyapatite crystallization in the desorption solution, which contained an abundant amount of phosphate as seed for suitable recovery condition. This finding suggested that MnFe2O4 could be a promising adsorbent for efficient phosphate removal. © 2015 Taylor & Francis Source

Huang H.,Chongqing University | Du X.,Chongqing University | Liu H.,Chongqing University | Bai H.,Chongqing Wangjiang Industry Co. | Zhu C.,Chongqing University
Chongqing Daxue Xuebao/Journal of Chongqing University | Year: 2015

As the key components of the wind turbine transmission, wind turbine drivetrain is always working under the complex and time-varing conditions, like flexible tower supporting, variable wind and changing load. Thus drivetrain is no wonder the weakest part for the wind turbine and its vibration characteristics determine the reliability and operating life of the wind turbine. This paper proposes a remote on-line test method for drivetrain vibration based on an intellectual monitoring unit named WindCon. The vibration characteristics of the commonly used multi-megawatt wind turbine are summoned through analyzing the collected data in different working conditions. The wind field results show that the vibration of drivetrain is relatively complex, and it's mainly manifested as a combination vibration of torsion, bending, and waving. Main frequencies of vibration of mainshaft, gearbox, and other parts in drivetrain are gear meshing frequencies and shaft rotating frequencies of each transmission stage especially high speed stage, and are accompanied by rotating frequencies modulation. ©, 2015, Chongqing Medical University. All right reserved. Source

Zhu C.,Chongqing University | Chen S.,Chongqing University | Song C.,Chongqing University | Liu H.,Chongqing University | And 2 more authors.
Journal of Mechanical Science and Technology | Year: 2015

The dynamic performance of a wind turbine drive train significantly influences the operation of an entire machine. In this work, a megawatt wind turbine drive train is subject to theoretical and experimental dynamic analysis. The method of rigid-flexible coupling multibody dynamics was applied to develop a dynamic model of the entire drive train. This model was then used to study the natural characteristics of the system. The blades, hub, main shaft, and speed-up gearbox in the dynamic model were modeled as flexible bodies. The potential resonances of the system were detected through Campbell and modal energy distribution analyses. Theoretical results show that the first-order natural frequency of the system is approximately 1.72 Hz. This frequency represents a torsional vibration mode, Moreover, resonances are not observed within the normal operating speed range of the drive train. An experimental remote real-time system was developed to monitor the torsional vibration of the drive train. This vibration was used to measure the torsional vibration of the system overall. The experimental results are consistent with the theoretical results. © 2015, The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg. Source

Zhu C.,Chongqing University | Chen S.,Chongqing University | Liu H.,Chongqing University | Huang H.,Chongqing University | And 2 more authors.
Journal of Mechanical Science and Technology | Year: 2014

A dynamic model of the drive train of a megawatt wind turbine is proposed in which the blades, the hub, the main shaft, and the speedup gearbox are assumed as flexibilities. The external excitation due to the measured load spectrum and the internal excitations due to the time-varying mesh stiffness, the transmission errors, and the meshing impacts within the gearbox are considered to predict the dynamic response of the system. Results show that the most vibration energy occurs at the speed-up gearbox, followed by the generator, and then the main shaft. An experimental remote real-time system is developed to monitor vibration performance of the drive train, with which the accelerations of components are detected. The experimental results are in accordance with the theoretical results. © 2014 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg. Source

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