Earticle

The sliding mode control problem is investigated for a class of nonlinear systems with the unmatched nonlinearity which satisfies a quadratic constraint. Based on Lyapunov stability theory, utilizing the singular value decomposition method, the sliding mode control is formulated to stabilize the considered systems. Meanwhile, the bounds on the nonlinear term which this type of systems can tolerate without going unstable are maximized. More importantly, an efficient sliding mode control law with tuned parameters is designed to guarantee the state variables to converge to the reference state in finite time and remain onto it in the subsequent time. Finally, simulation results are presented to illustrate the effectiveness of the control strategy.

Recently, we have witnessed the emergence of new data stream management systems that can scale up to a large number of machines for the real-time processing of big data. These systems typically provide a procedural programming interface with their own APIs. However, to enable the rapid development of applications, it is desirable to support a declarative interface with clear processing semantics, such as window SQL. This paper examines the programming interfaces of the state-of-the-art data stream management systems and discusses the necessity of SQL support to help users write stream queries easily and in an integrated manner.

Recently microblog has become a popular Internet service. Yet, the abundance of micrblog floods users with huge volumes of information and poses a great challenge in terms of information overload. Recommender systems aim to alleviate information overload over microbog users by presenting the most attractive and relevant content. Many recommendation approaches have been proposed by leveraging the social relationships in microblog. To prove the feasibility of users’ social relationships as the bases of recommendation in microblog, we examine the correlations of social relationships and user interest similarities in microblog. Using real-world data set, we find that social relationship indicates positive connection with user interest similarity in microblog, but the positive connection is not strong. We also observe strong positive correlation between reciprocal social relationship and user interest similarity in microblog. As to users’ interaction, we find that the number of interaction between two users in social relation is a strong signal that controls users’ interest similarity. We then apply these findings to recommendation application in microblog to improve the accuracy of recommendation. The experiment on real-world data set shows that our findings are useful for recommendation.

In the mine protection of high voltage power grid, quick and accurate detection of network parameters and power quality parameters is significant for the reliability, security and continuity of the power supply system. Fast AC sampling algorithm with low computational complexity and high precision can obtain a variety of electrical parameters accurately, to guarantee real-time system monitoring and protection. In this paper, in-depth study on short-circuit protection and overload protection works of the mine high voltage power grid is undertaken, the advantages and disadvantages of Fourier algorithm and root mean square (RMS) algorithm in AC sampling algorithm as well as the application conditions are analyzed. On this basis, a fast Fourier AC sampling algorithm applied to mine high voltage grid parameters detection is proposed, and the algorithm is analyzed; at the same time, hardware circuit of mine high voltage power protection system and related software are designed based on Fast Fourier AC sampling algorithm, and the system is verified by experiments. Experimental results show that the system based on fast Fourier AC sampling algorithm is stable, and network parameter detection is accurate, with certain application value.

This paper presents a smart wearable device cooperating with smartphones to measure and utilize human activity and biometric data such as motion tracking, photoplethysmography (PPG), skin temperature (SKT), and galvanic skin response (GSR). It is comfortably designed and implemented as a wristband-type device and provides wireless Bluetooth Low Energy (BLE) connection to smartphones based on the Android operating system. According to the predefined packet format and control commands, the proposed smart wearable device can transmit measured sensing data and update its firmware. Implemention results verify the feasibility and usability of the proposed smart wearable device. It can be applied to various healthcare and wellness services or even emotional game applications.

To address the non-linear error and tool collision or tool interference introduced by the rotation axis, control strategy of five-axis machining tool axis vector interpolation based on NURBS surface is proposed. By using NURBS surface reconstruction ideas, after node vectors are inverse computed, it is inserted in the U and V-parameter direction of the surface. Then surface control points are anti-calculated, and the data points of shape values on the surface are determined which is tool cutting contacts point. By using normal vector of surface and combining machine tool kinematics analysis results, the rotation angle of the two rotary axes are calculated. And then, the tool axis vector to be interpolated is determined. Simulation results show that the algorithm can effectively improve the accuracy of five-axis CNC machining, and verify the effectiveness and practicality of the algorithm.

Most of existing doorway systems are directly controlled by a central system. Most of central control systems have the function of fingerprint recognition, biometrics (face, iris), encryption key and so on. However, it costs a lot of money and may be vulnerable to security, and inspection history management is inconvenient because most of I/O devices like readers are connected with external networks. We will study automatic doorway control systems based on authorized encryption key from servers under Bluetooth local networks linked with smart phones. We aimed to construct a doorway Access control system by using smart phones. In addition to this, the server we studied can control automatic doorway systems and access authorization of visitors including inspection history management of engineers. It also provides real time monitoring function by transmitting the status information to smart phones.

The type-2 fuzzy sets (T2FSs) provide us additional degrees of freedom to represent the uncertainty and the fuzziness of the real world. As a special kind of T2FSs, interval type-2 fuzzy sets (IT2FSs), whose operations are much simpler than the ones of general T2FSs. So the research of IT2FSs has become a hot topic in decision-making field in recent years. In this paper, firstly, we introduce the operational laws of IT2FSs, and propose a distance measure of IT2FSs. Secondly, we present a novel approach for handling multiple attributes decision-making problems with IT2FSs, on base of the idea of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). The method proposed is more practical and flexible because it not only consider the importance weights, but also reflect the decision strategies that both are essential to different decision makers for choosing different decision tactics. Finally, a numerical example of service quality assessment is used to verify the effectiveness of the presented approach.

Buses are the only public transportation available to citizens in cities that do not belong to a metropolitan area. The interval between two consecutive bus departure times is pretty long in these cities. Therefore, a bus information system (BIS) that provides a variety of useful information to users is desperately needed in these cities. One type of useful information that BISs provide is how to get from the starting bus stop to the destination bus stop. In this paper, we analyze one of the existing algorithms that finds efficient bus travel paths and point out its shortcomings. Then, we design and implement an algorithm that mitigates the shortcomings. Implementation details of the algorithm are also discussed.

Combining characteristics of the greenhouse and the problems existing in the process of environment parameter measurement, an environment parameter intelligent measurement system based on GPRS has been put forward and the hardware circuit and the software design of the system have been completed. The system is mainly composed of a parameter measuring terminal, GPRS network and a monitoring host. The parameter measuring terminal with the core of single chip microcomputer can obtain environment parameters on the scene through a high precision sensor, and then, it sends the data through the GPRS module based on wireless network to the monitoring center, and the monitoring host will receive data that will be real-time displayed. The system has the characteristics of good expansibility, low cost and high accuracy so that it can meet the requirements of wireless acquisition of remote data and has broad prospects of application and a good promotional value.

Attitude estimation has a wide range of applications including aerial (UAVs for example), underwater (ROVs for instance), navigation systems, robotics, games, augmented reality system, industrial and so on. Extensive research over decades in this field resulted in a number of powerful estimators; complex like Kalman based algorithms as well as simple such as complementary filters & the kinds. For applications where computational simplicity is of prime concern, complementary filters have proven efficiency. This paper presents a comparative study of computationally simple algorithms naming Explicit Complementary Filter (ECF) and Gradient Descent based Complementary Filter (GDCF) along with computationally demanding extended Kalman filter-a de-facto standard for attitude estimation so far, regarding attitude estimation based on MEMS IMU. An alternative would be the variants of complementary filter; sufficiently efficient and simple scheme to avoid computational complexity.Performance of these estimators is evaluated for Euler angle estimation using both simulated data from Matlab and experimental data from MPU6050 IMU. The assessment is based on the root mean square error computation for these algorithms. Moreover, the algorithms adjustable parameters were exploited for a range of values in the hunt for perfection

Fast Fourier Transform plays a very important role in signal analysis, but the Fast Fourier Transform traditional mutation fault fan are unable to analyze the trend of fault features, the beginning and the end, and these signals often contain important information, the fault at the same time, the local signal analysis Fast Fourier Transform of fault are also incapable of action. The method of multi scale wavelet theories and Fast Fourier Transform are combined, make up for the deficiency of the Fast Fourier Transform, and the method is applied to the fault diagnosis of fan, and achieved good results, experiments show that, this method can effectively improve the accuracy of fault diagnosis. Wavelet packet analysis due to the high, the low frequency part of the signal local refinement and retention time domain features of the original signal, which has good time-frequency localization characteristics, it can effectively identify the non-stationary signal, to achieve the purpose of fault diagnosis, get more and more extensive application in the field of fault diagnosis. Signal generating fan running most of the non-stationary signal, the wavelet packet analysis technology is used to diagnose the fault has practical significance.

In order to reduce the node position error of DV-Hop algorithm in wireless sensor network, the artificial bee colony algorithm is introduced to design the DV-Hop algorithm. A new ABCDV-Hop (Artificial Bee Colony DV-Hop) algorithm is proposed in this paper. Based on the traditional DV-Hop algorithm, by using the minimum hops of nodes and position information of anchor nodes, the average distance per hop is solved by artificial bee colony algorithm to make it more close to the actual value. The simulation results show that compared with the traditional DV-Hop algorithm, the improved algorithm can effectively reduce the positioning error without increasing the node hardware overhead.

The passengers suffer much inconvenience in a crowded subway during rush hour. The hybrid passenger density estimation (PDE) or information (PDI) system is proposed for maximizing the metro-users' convenience and saving their elapsed time to the destination. The hybrid PDIS technology is comprised of image processing for extracting passengers' head colors/motion vectors and RFID/NFC sensing for measuring the number of passengers. As a result, we can estimate fully the state of passenger density. As the system and its administrator reflect the appr

Energy efficiency is the primary goal of wireless sensor network. An energy conversion model in wireless sensor network node’s different state is established by an analysis of energy consumption of wireless sensor network, node composition and working state, considering the wireless sensor network node’s working condition and the other nodes’ data acquisition, transmission and other factors within the wireless sensor network. Optimized Kalman filtering is used for estimating the event information to be transmitted. We can obtain the more accurate distance between the nodes by using the maximum likelihood estimation. Also we can derive the time value of uncertain events occurring in the wireless sensor network by using fuzzy predictor according to the distance between nodes and the amount of information to be transmitted. Then the wireless sensor nodes state transition can be controlled intelligently through combining its occurrence with the time value of deterministic event nodes and the input signal of the nodes. Simulation and experimental results show that energy-saving effect is very obvious by this state conversion strategy of energy saving for a large data quantity and data frequent acquisition.

In this paper, we investigate the trajectory tracking problem for the 6-DOF quadrotor aircraft with both internal uncertainties and external disturbances. The nonlinear system model is established based on Modified Rodrigues Parameters and the error model is then obtained based on the trajectory tracking task. To deal with the cascade property of the controlled objective, the system is divided into the translational and rotational subsystem, respectively. Hence, a hierarchical technique is introduced to implement the control system. Then, nonlinear disturbance observer based backstepping control strategy is proposed based on each subsystem. Global stability of the closed-loop system is analyzed based on Lyapunov theorem. Simulation results verify the effectiveness of the proposed control scheme.

IoT (Internet of Things) based underground risk assessment system surrounding water pipes enables an advanced monitoring and prediction for unexpected underground hazards such as abrupt road-side subsidence and urban sinkholes due to a leak in water pipes. For the development of successful assessment technology, the PSU (Pipe Safety Unit) is under development which detects the leakage and movement of water pipes. Then, the IoT-based underground risk assessment system surrounding water pipes will be proposed. The system consists of early detection tools for underground events and correspondence services, by analyzing leakage and movement data collected from PSU. These methods must be continuous and reliable, and cover certain block area ranging a few kilometers, for properly applying to regional water supply changes.

In view of the problems of the home monitoring robot obstacle-navigation performance is poor and obstacle to restore stability is slow, according to the structural characteristics of home monitoring robot, developing a six wheels home monitoring robot, the main features of which lies in the use of independent suspension system combines a double wishbone type and McPherson independent suspension system, effectively improve the obstacle properties and stability of home monitoring robot. Based on the experimental prototype, carried out the experiment of robot obstacle movement, and proved that the structure has the performance of good stability and good obstacle.

Harmonic drive is a kind of new gear drives developed in the past decades, and it consists of flexspline, circular spline and wave generator. Due to thermal deformations and additional strains by the effects of temperature in harmonic drive, the mechanical property of harmonic drive is seriously influenced by its deformations. The harmonic drive mechanical characteristics are studied under the thermal loading, and heat-structure coupling is deduced in solving mathematical model of stress. The heat-structure coupling analysis of Harmonic Drive is solved, including stress and deformation law to explore new structures.

The purpose of this research was to make optimal design on capacity and number of multi-objective rainwater detention system that can satisfy irrigation and dimension of flood prevention as well as acquiring water source such as fire water, landscape water, and water for living in the medium and small scale basin where flood occurs frequently during focused raining due to the increase of impermeability layer. The methodology executed in this research was designed so that the construction fee and maintenance/management fee consumed in the rainwater detention system become minimized while various benefits including water and sewage cost, dam construction fee reduction, and flood damage cost reduction fee can be maximized. When considering the installation of rainwater detention system in the already developed cities or new cities, more effective design can be possible when using the same method.

In this study an attempt has been made to study the hydrodynamic performance of pumpjet propulsor. Numerical investigation based on the Reynolds Averaged Navier-Stokes (RANS) computational fluid dynamics (CFD) method using structured grid, SST k-ω turbulence model has been carried out. The grid independence inspection is applied to verify accuracy of numerical simulation. The numerical predictions of hydrodynamic performance for pumpjet propulsor are carried out with different advance ratios. Results show that the coefficient curves of thrust and torque that indicates the rotor provides the main thrust of propulsor and the balance performance of propulsor is generally satisfactory. Additionally, the curve of propulsor efficiency is in good agreement with experimental data. Furthermore, the pressure distributions around rotor and stator blades are reasonable. Beyond that, the existence of tip clearance accounts for the appearance of tip vortex that leads to a further loss in efficiency and a probability of cavitation phenomenon.

Like the Sudoku puzzle, the magic square involves recreational mathematical contexts and has attracted considerable attention. Although there are many researches available, few of them could provide an efficient solution for constructing all magic squares of order four. In this paper, we firstly formulate constraints of magic squares of order four by a collection of linear equations and provide an intuitive but computationally infeasible solution to these equations. Then, we propose an efficient algorithm for constructing all magic squares of order four. The algorithm transforms solving these equations into finding all possible permutations of seven free variables from sixteen consecutive natural integers based on the Gaussian Elimination method. Furthermore, we show the effectiveness of the proposed algorithm by 48 magic squares in the experimental section.

This paper addresses an optimal train trajectory planning and tracking problem for automatic train operation (ATO) with consideration of the train model uncertainty and constraints. Based on the discrete linear multi-points train model, an ATO control algorithm is presented to track piecewise reference by using model predictive control with constraints tightening such that the feasibility and robust convergence of this algorithm are guaranteed under the varying running resistance, automatic train protection (ATP) constraint, and train motor physical limits. Specifically, the features of the algorithm are: (i) taking traction and braking force of locomotives and braking force of carriges into account explicitly; (ii) integrating constraints tightening approach into piecewise reference tracking problem to ensure robustness; (iii) combining the optimal planning level and tracking control level together. Finally two case studies are conducted to verify the effectiveness of the algorithm.

This paper introduces an algorithm of wavelet biological image denoising integrated into quantum-inspired method, which is based on the basic principles of quantum mechanics. The quantum-inspired method is applied to estimate the respective probability of wavelet coefficients of the noise and signal of the biological image, then dynamically self-adapt to estimate the semi-soft threshold of wavelet coefficients, so as to protect the signal wavelet coefficients and filter the noise wavelet coefficient. Therefore, the proposed algorithm can restore the noise biological image and protect details of the biological image. Experimental results show that the proposed algorithm can improve the image quality and it is better than other denoising algorithms.

By introducing a parameter  and using the Euler-Maclaurin expansion, we establish an inequality of a weight coefficient. Using this inequality, we derive a new reverse Hilbert's type inequality. As applications, an equivalent form is obtained.

To establish secure communication, authenticated key agreement, which combines user authentication and key agreement, is the basic services for many security and privacy services over wireless sensor networks (WSNs). Recently, Jiang et al. proposed an efficient authenticated key agreement scheme with unlinkability for WSNs. Unfortunately, this paper shows two weaknesses in Jiang et al.’s scheme, which are the problem of global time synchronization requirement and the lack of forward secrecy. After that, this paper proposes an enhanced authenticated key agreement scheme with forward secrecy to remedy Jiang et al.’s scheme. The proposed scheme does not use timestamp that requires the global time synchronization and provides forward secrecy. It provides user anonymity and un-traceability by adopting dynamic identifier depending on each session dependent random number.

This paper addresses the bottom-following control problem of an underactuated autonomous underwater vehicle (AUV) in the presence of ocean currents and model parameters uncertainties. The Serret-Frenet frame is used to describe the bottom following of the AUV. An extra degree of freedom for controller design is introduced. The extra degree of freedom makes the virtual AUV can regulate its velocity along with the real AUV. Based on Lyapunov theory and backstepping techniques, a nonlinear adaptive control law is derived. The control law yields convergence of the AUV to the desired path asymptotically. Simulations results show the effectiveness and robustness of the derived controllers.

A fuzzy integral sliding mode control method based on the finite time stable theory and integral sliding mode control theory is proposed to solve a class of complex network problems. The complex networks are expressed by T-S fuzzy models with bounded approximation errors by using the approximation capability of T-S fuzzy models. The paper proposes fuzzy dynamic integral sliding mode control scheme and the scheme is designed for the complex networks based on their T-S fuzzy approximation models. The simulation result shows that the trajectories of the closed-loop control system are kept on the sliding surface almost since the initial time. And the sliding motion of the closed-loop control system involving the original nonlinear system can be shown to be semi globally asymptotically stable. The controller can make system convergence in finite time and reduce the system buffeting effectively.

Multipath is one of the main error sources that influence GNSS precise relative positioning. To mitigate multipath error, this paper starts from study of variation characteristics of signal-to-noise ratio (SNR) measurements, and then proposes a satellite selection method based on SNR fluctuation for static relative positioning. Test results indicate that positioning accuracy can be significantly improved by the proposed method.