Investigation of dynamic characteristics of planetary gear stage in wind turbine considering voltage dip

Jianjun Tan,Caichao Zhu,Chaosheng Song,Xiangyang Xu,Zi Wang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.9

The transient variation of electrical parameters makes system loads fluctuate and reduces bearing capacity when the grid voltage dips. This work proposes an electromechanical coupling dynamic model of the wind turbine drivetrain to build a dynamic interconnection between the electric and drivetrain subsystems. The drivetrain subsystem that includes an improved model of the planetary gear stage is developed and validated. This improved model considers the carrier and planet bearing clearances, the connection relationship among the carrier, main shaft, and planets as well as the flexibilities of the main shaft and parallel stage shafts. The influences of the carrier bearing clearances, non-torque load and planet position angle on planet bearing loads are investigated under the low-voltage ride through (LVRT) event. The results indicate that as the LVRT occurs, the planet bearing loads reduce below the minimum requisite with a high, fluctuating system speed; considering the bearing clearances, the impacts occur in the planet bearing in the minimum load zone followed by significant stress variation; the non-torque load suppresses the planet bearing impacts in a limited range of carrier bearing clearance; the planet position angle has a significant effect on the planet bearing impacts because of the asymmetry of load and structure of the planetary gear stage.

Trajectory Tracking Control for Wheeled Mobile Robots with Kinematic Parameter Uncertainty

Jianjun Bai,Jian Du,Tianlong Li,Yun Chen 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.5

The trajectory tracking control for a class of wheeled mobile robots (WMRs) with kinematic parameter uncertainty is studied in this paper. Firstly, a new Lyapunov function is proposed, based on which, a new kinematic controller for WMRs without parameter uncertainty is designed to make the tracking error system asymptotically stable. Secondly, the parameter uncertainty of the kinematic model is taken into consideration and an modified adaptive law is designed to deal with the uncertainty. Then, in order to improve the tracking performance, a selftuning algorithm of the parameters of the controllers is proposed based on neural networks. Finally, numerical examples are given to illustrate the effectiveness of the proposed method.

Adaptive Finite Time Control for Wearable Exoskeletons Based on Ultra-local Model and Radial Basis Function Neural Network

Jianjun Sun,Jie Wang,Peng Yang,Yan Zhang,Lingling Chen 제어·로봇·시스템학회 2021 International Journal of Control, Automation, and Vol.19 No.2

This paper investigates an adaptive finite time control scheme for wearable exoskeletons to realize trajectory tracking control. The main feature of the proposed scheme is model-free in which no dynamic models are required except for the input and output data. Firstly, a second order ultra-local model is employed to replace the complex dynamic model of wearable exoskeleton as the controlled object, which is a novel designed model. In addition, a nonsingular fast terminal sliding surface is proposed to design the controller to guarantee the finite time convergence of tracking errors, and a radial basis function (RBF) neural network is developed to approximate the lumped disturbance in the ultra-local model. Then the stability of closed-loop system is proved by Lyapunov theory. Finally, to validate the proposed control scheme, virtual prototype is designed in SolidWorks and transferred to MATLAB, then visual simulation program is implemented based on SimMechanics. What’s more, reference trajectories are extracted from the measured data of DELSYS Electromyography (EMG) recording system. Theeffectiveness of proposed scheme is demonstrated by the simulation results.

Enhanced remote-sensing scale for wind damage assessment

Jianjun Luo,Daan Liang,Cagdas Kafali,Ruilong Li,Tanya M. Brown 한국풍공학회 2014 Wind and Structures, An International Journal (WAS Vol.19 No.3

This study has developed an Enhanced Remote-Sensing (ERS) scale to improve the accuracy and efficiency of using remote-sensing images of residential building to predict their damage conditions. The new scale, by incorporating multiple damage states observable on remote-sensing imagery, substantially reduces measurement errors and increases the amount of information retained. A ground damage survey was conducted six days after the Joplin EF 5 tornado in 2011. A total of 1,400 one- and two-family residences (FR12) were selected and their damage states were evaluated based on Degree of Damage (DOD) in the Enhanced Fujita (EF) scale. A subsequent remote-sensing survey was performed to rate damages with the ERS scale using high-resolution aerial imagery. Results from Ordinary Least Square regression indicate that ERS-derived damage states could reliably predict the ground level damage with 94% of variance in DOD explained by ERS. The superior performance is mainly because ERS extracts more information. The regression model developed can be used for future rapid assessment of tornado damages. In addition, this study provides strong empirical evidence for the effectiveness of the ERS scale and remote-sensing technology for assessment of damages from tornadoes and other wind events.

Construction Scheme of NSFC Open Access Library

Jianjun Li,Minshe Zhang,Dong Li,Wei Zhang,Jin Wang 보안공학연구지원센터 2015 International Journal of Security and Its Applicat Vol.9 No.8

With the fast development of Open Access (OA) in recent years, it helps stimulate free scientific achievements propagation via Internet and promote academic exchange and fast publishing in an efficient and cheap way. In this paper, we propose a construction scheme of our Natural Science Foundation of China (NSFC) open access library which is under development recently. We first propose our overall architecture for OA library. Then, we present detailed design from upper layer OA webpage with 3-level display hierarchy to the middle layer some key function modules. Next, bottom layer raw data acquisition module and other important system function modules like interface module, people management and security modules are explained with illustrative figures and table.

Electromechanical analysis of 2-2 cement-based piezoelectric transducers in series electrically

Jianjun Wang,Zhifei Shi 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.14 No.3

his paper aims to present the analytical solutions of 2-2 cement based piezoelectric transducers in series electrically based on the theory of piezo-elastic dynamics. The solutions of two different kinds of 2-2 cement based piezoelectric transducers under external harmonic load are obtained by using the displacement method. The effects of electrical connection of piezoelectric layers, loading frequency, thickness and distance of piezoelectric layers on the characteristics of the transducers are discussed. Comparisons with other related experimental investigations are also given, and good agreement is found. The proposed 2-2 cement based piezoelectric transducers have a great potential application in monitoring structural health in civil engineering and capturing mechanical energy or monitoring train-running safety in railway system and traffic safety in road system.

Analysis of HEVC Coding Standard

Jianjun Wang,Li Zhou,Tao Sun 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.7

HEVC video coding standard can achieve an average of 50% bit-rate saving, transmitting nearly the same visual quality, compared with the H.264/AVC High Profile. This paper focuses on the key features of the HEVC standard. Then it analyzes the complexity of the HEVC standard by profiling the HEVC reference software HM12.0 which is released by JCT-VC community with Intel Core i7 processor. The experiment covers different settings for a wide variety of video sequences, with the resolutions ranging from 240p to 1600p. The evaluation result shows that the HEVC standard can achieve a doubling in coding efficiency at the cost of increasing the complexity slightly. When the sequences are coded in all-intra or random-access configurations, intra prediction, loop filter, inverse transform and motion compensation are the most complex components for HEVC decoder. The motion compensation part should be given lots of consideration since it can take nearly half of the decoding time. The quantization parameter (QP) also has obvious influences on the complexity of the decoder. Besides, in practice, the HM decoder is not able to decode video content with 1080p or higher resolutions for real-time applications.

An Improved Attention-based Bidirectional LSTM Model for Cyanobacterial Bloom Prediction

Jianjun Ni,Ruping Liu,Guangyi Tang,Yingjuan Xie 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.10

Cyanobacterial blooms are one of the most serious water pollution problems for freshwater lakes. The treatment of blooms requires a lot of material and financial resources, so an early accurate prediction of cyanobacterial blooms is a very important way to deal with the outbreak of them. But it is challenging to predict the cyanobacterial blooms due to the uncertainty and complexity of their growth process. To deal with this problem, an improved attention-based bidirectional long short-term memory (LSTM) model is proposed in this paper, to make multistep predictions of chlorophyll-a concentration, which is a recognized characterization of algae activity. Firstly, the convolutional neural network (CNN) is used to extract data features and spatiotemporal correlation. Secondly, the bidirectional LSTM network (BiLSTM) is used to predict the concentration of chlorophyll-a based on the extracted features. Finally, the attention mechanism is used to calculate the weights for the characteristic factors that affect the chlorophyll-a concentration. At last, some experiments are carried out based on the real monitoring data of a platform in the Taihu Lake area. Compared with the prediction results of the other four state-of-the-art deep learning methods, the results show that the proposed method in this paper has the highest prediction accuracy.

Design and Implementation of Knowledge based Cloud Platform for NSFC Service System

Jianjun Li,Yuhui Zheng,Jin Wang 보안공학연구지원센터 2016 International Journal of Grid and Distributed Comp Vol.9 No.12

With the quickly development of Natural Science Foundation of China (NSFC) foundations, management of mass fund-relevant digital data, such as researchers and institutions, academic achievement, funds and so on, is becoming more and more important for supporting basic scientific research. In this paper, we fully introduce the design and implementation of NSFC cloud platform that will be implemented in the service system of knowledge base. Firstly, the whole cloud platform architecture is presented. Then we introduce the system software and equipment environment of our platform. Lastly, we present the construction of private cloud, network components, storage components, and computing components, respectively, with illustrative figures and tables.

Load regulation of the heat supply unit assisted by the energy storage in thermal networks via a reference model-based controller

Jianjun Shu,Gengjin Shi 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11

With the grid-connection of renewable energy such as wind and solar, the coal-fired units are required to participate in deep-peak-shaving and respond to the automatic generation control (AGC) command as fast as possible. As a result, energy storage in thermal networks is usually utilized to assist the load regulation of the unit. However, the traditional proportional-Integral (PI) controller is unable to obtain satisfactory performance due to its simple structure, and its tuning is still a challenge for practitioners because of the compromise between parameters. To solve this problem, a reference model (RM)-based controller—desired dynamic equational (DDE)-PI is designed to regulate the load of the unit since it can obtain good tracking performance and readily eliminate the compromise. Simulation results demonstrate that DDE-PI can not only regulate the load with fast and moderate tracking performance but also improve the stability of the supply steam pressure, which shows its promising prospects in the future power industry with the increasing demand to integrate more renewable energy into the grid.