1,256 publications from this institution
This paper is concerned with the robust control problems for the synchronization of master-slave chaotic systems with disturbance input.By constructing a series of Lyapunov functions, novel H ∞ robust synchronization controllers are designed, whose control regulation possess the characteristic of simpleness and explicitness.Finally, numerical simulations are provided to demonstrate the eectiveness of the proposed techniques.
The problem of robust reliable tracking control on the omnidirectional rehabilitative training walker is examined. The new nonlinear redundant input method is proposed when one wheel actuator fault occurs. The aim of the study is to design an asymptotically stable controller that can guarantee the safety of the user and ensure tracking on a training path planned by a physical therapist. The redundant degrees of freedom safety control and the asymptotically zero state detectable concept of the walker are presented, the model of redundant degree is constructed, and the property of center of gravity constant shift is obtained. A controller that can satisfy asymptotic stability is obtained using a common Lyapunov function for admissible uncertainties resulting from an actuator fault. Simulation results confirm the effectiveness of the proposed method and verify that the walker can provide safe sequential motion when one wheel actuator is at fault.
Current signal monitoring (CSM) can be used as an effective tool for diagnosing broken rotor bars fault in induction motors. In this paper, fault diagnosis and classification based on artificial neural networks (ANNs) is done in two stages. In the first stage, a filter is designed to remove irrelevant fault components (such as noise) of current signals. The coefficients of the filter are obtained by least square (LS) algorithm. Then by extracting suitable time domain features from filter's output, a neural network is trained for fault classification. The output vector of this network is represented in one of four categories that includes healthy mode, a 5 mm crack on a bar, one broken bar, and two broken bar modes. An optimum structure of the neural network is obtained via particle swarm optimization (PSO) algorithm.
Aerial image registration is one of the bases in many aerospace applications, such as aerial reconnaissance and aerial mapping. In this paper, we propose a novel aerial image registration algorithm which is based on Gaussian mixture models. First of all, considering the characters of the aerial images, the work uses a shape feature detector which computes the boundaries of regions with nearly the same gray-value to extract invariant feature. Then, a Gaussian mixture models (GMM) based image registration model is built and solved to estimate the transformation matrix between two aerial images. Furthermore, the proposed method is applied on real aerial images, and the results demonstrate the improved performance of the proposed algorithm.
Adaptive dynamic programming (ADP) technique is adopted in this work to investigate the optimal control problem of Markovian jump systems. By utilizing Bellman’s optimality principle, a discrete Hamilton Jacobi Bellman (HJB) equation is established to design the optimal controller for the system under consideration. Then, based on value iteration, a new ADP algorithm is proposed for finding the solution of the established HJB equation. It is proven that the iterative solution sequence generated by the developed ADP iterative approach under zero initial values is monotonically convergent. Neural networks are constructed to accomplish the presented value iteration ADP algorithm. At last, simulation researches for two Markovian jump systems demonstrate the effectiveness of the proposed optimal control method.
No abstract is provided for this article.
In this article, the issue of sliding mode control for nonlinear stochastic Markovian jump systems with uncertain time-varying delay is investigated. Considering the system state measurements and the state-dependent disturbances are not available for feedback purposes, an observer-based adaptive control strategy is proposed. Based on the decomposition of the input matrices, the state-space representation of the system is turned into a regular form with the aid of T-S fuzzy models first. Then, a fuzzy observer system is constructed, which could be transformed into two lower order subsystems. By choosing a common linear switching surface, on which it also obtains linear sliding mode dynamics in a simple form. Further, an adaptive controller is synthesized relying on the bounded system delay information to ensure the estimated states driven on the predefined sliding surface and remain the sliding motion. Also, the stochastic stability analysis of the sliding mode dynamics is undertaken with two types of transition rates, and an interesting result reveals that the stability for the dynamics with type of uncertain transition rates may cover the completely known type. Finally, a single-link robot arm model is provided to verify the validity of the proposed method.
An outline of health management for OWFs has been detailed in this chapter with description of various important elements. The need for such farm level management is explained and benefits are discussed. Key gaps to be filled in order to realize such a system are identified. The proposed health management system is mainly based on the existing knowledge of fleet-level management in the aerospace sector. Health management is much broader than CM; there are a number of aspects beyond the prognostics capabilities that are to be designed in order to arrive at a comprehensive maintenance management scheme. A comprehensive maintenance program that is sensitive to the health of the assets and adapts maintenance schedule accordingly, depending upon resource availability, logistics and inventory, is key to cost optimization while ensuring reliability and availability. The advances in CM and diagnostics in wind energy are in the right direction, and many of them are building blocks for health management. Offshore wind faces a number of unique challenges that can be satisfactorily addressed by following a suitable systematic approach. RCM implementation appears to be the most suitable as it encompasses other maintenance strategies and is suitable for farm-level deployment.
The emerging big data allows educational studies to examine teaching and learning behaviors over time and at scale. Less available is population-representative big data. This paper builds the first nationally representative sample of teachers’ online curation on a social media platform (i.e. Pinterest), the Public Instructional Network of School Resources (PINSR). This effort includes developing a big-rich data sampling framework, integrating social media data with administrative and census “ground truth” sources, and validating the population representativeness. Finally, we employ PINSR and present a worked example of teachers’ social media curation behavioral patterns across regions and time.
کشاورزی بزرگترین مصرفکنندهی منابع آب شیرین است و بنابراین هنجارهای و رفتارهای کشاورزان نقشی کلیدی در نظام مدیریت منابع آب دارند. هدف اصلی پژوهش حاضر، بررسی تعیینکنندههای هنجارهای اخلاقی و اسناد مسئولیت در زمینهی حفاظت آب بوده است. این پژوهش از نوع پژوهشهای توصیفیـ همبستگی است که با استفاده از روش پیمایش انجام شد. جامعه آماری مورد مطالعه، کشاورزان شهرستانهای مهاباد و میاندوآب در استان آذربایجان غربی بودند که 380 نفر از آنها با استفاده از روش نمونهگیری تصادفی طبقهای با انتساب متناسب بهعنوان نمونه انتخاب شدند. ابزار مطالعه، پرسشنامهای بود که روایی آن توسط گروهی از متخصصان به تأیید رسید و پایایی آن با استفاده از ضریب آلفای کرونباخ مورد تأیید قرار گرفت. نتایج نشان داد که متغیرهای نگرانی نسبت به کمبود آب، اسناد مسئولیت و دلبستگی مکانی، اثر مثبت و معنیداری بر هنجارهای اخلاقی در زمینهی حفاظت آب داشتند. همچنین، ارزش جمعگرایانه بهصورت مثبت و معنیداری، اسناد مسئولیت را تحت تأثیر قرار میدهد، این در حالی بود که ارزش فردگرایانه اثر منفی و معنیداری بر اسناد مسئولیت داشت. همچنین نتایج نشان داد که متغیرهای مستقل پژوهش حاضر، توانایی پیشبینی در حدود 58 درصد از تغییرات واریانس متغیر وابسته را دارا میباشند.
Using Haar wavelets, a computational method is presented to determine the piecewise constant feedback controls for a finite-time linear optimal control problem of a time-varying state-delayed system. The method is simple and computationally advantageous. The approximated optimal trajectory and optimal control are calculated using Haar wavelet integral operational matrix, Haar wavelet product operational matrix and Haar wavelet delay operational matrix. An illustrative example is included to demonstrate the validity and applicability of the technique
The non-fragile fault-tolerant control for a class of nonlinear Markovian jump systems with intermittent multiple actuator faults is addressed in this study. The nonlinearity in the considered system is assumed to satisfy sector constraint. Multiple Markov chains are introduced to model the multiple intermittent actuator faults, which is in a multiplicative form. To ensure the fault tolerance of the closed-loop system in the presence of potential controller perturbation, a new non-fragile fault-tolerant controller is designed, which can stabilize the resulting closed-loop system and further satisfy a prescribed performance index. After appropriately synthesizing the fault model that dominated by multiple Markov chains and the underlying nonlinear Markovian jump system, a set of sufficient conditions for the considered problem focusing on the controller design is derived with both known and partially known transition probabilities, where the controller can be determined via a convex optimization procedure. An example is given to illustrate the effectiveness of the proposed controller.
Summary The design of tracking control problem and compensation of disturbance for switched neutral systems with multiple time‐delays and external disturbances are addressed in this paper. In this regard, a modified repetitive control technique based on the Matausek‐Micic modified Smith predictor approach is being implemented, which assures the exact tracking performance and disturbance attenuation with high precision in the considered system. To be specific, the integration of transfer function with modified Smith predictor block not only provides the accurate compensation of input time‐delays but also ensures the exact estimation and attenuation of external disturbances effectually. Furthermore, according to Lyapunov stability approach combined with average‐dwell‐time technique, a group of adequate conditions is derived in the form of matrix inequalities. Simultaneously, by solving the established matrix inequalities using available software the controller gain matrices are calculated. Ultimately, the simulation results of three numerical examples are presented to validate the efficiency and dominance of the suggested control procedure.
The demand for low-cost and low-power decoder chips has resulted in renewed interest in low-complexity decoding algorithms. In this paper a novel modification of the Max-Log-MAP algorithm is proposed for use in a turbo decoding process. This is achieved by scaling the a priori information by correction weights at each iteration, in order to maximize the exchange of mutual information between the component decoders. It is shown that the proposed technique results in a performance which approaches that of a turbo decoder using the optimum MAP algorithm, while maintaining the advantages of low complexity and insensitivity to input scaling inherent in the Max-Log-MAP algorithm. A second contribution of this paper is a method for off-line computation of the optimum weight values. The convergence behaviour of the proposed decoder is analysed via extrinsic information transfer (EXIT) charts.
No abstract is provided for this article.
This paper considers the problems of delay-dependent stability and l 1-gain analysis for a class of positive two-dimensional (2D) Takagi–Sugeno (T–S) fuzzy linear systems with state delays described by the second FM model. Firstly, the co-positive type Lyapunov function method is applied to establish sufficient conditions of asymptotical stability for the addressed positive 2D T–S fuzzy system. Then, the l 1-gain performance analysis for the positive 2D T–S fuzzy delayed system is studied. All the obtained results are formulated in the form of linear matrix inequalities (LMIs) which are computationally tractable. Finally, an illustrative example is given to verify the effectiveness of the proposed method.
The authors are concerned with the accuracy of azimuth and elevation estimates provided by a planar array of sensors and its relation to the array manifold differential geometry. The paper builds on previously published results regarding the influence of manifold differential geometry on the detection and resolution capabilities of linear arrays. The manifold of a planar array is introduced in terms of two families of constant-azimuth and constant-elevation curves, and their differential geometry is analysed as a function of array configuration. Circular approximation is subsequently employed to derive novel expressions for the Cramer–Rao lower bound on azimuth and elevation estimates in terms of the arc lengths and first curvatures of the respective constant-parameter manifold curves. The scenarios considered include the cases of a single emitter as well as that of two closely spaced uncorrelated emitters of arbitrary powers. The results obtained are demonstrated for the cases of two practical array configurations.