1,256 publications from this institution
In this article, a computational method based on Haar wavelet in time-domain for solving the problem of optimal control of the linear time invariant systems for any finite time interval is proposed. Haar wavelet integral operational matrix and the properties of Kronecker product are utilized to find the approximated optimal trajectory and optimal control law of the linear systems with respect to a quadratic cost function by solving only the linear algebraic equations. It is shown that parameter estimation of linear system can be done easily using the idea proposed. On the basis of Haar function properties, the results of the article, which include the time information, are illustrated in two examples.
This paper deals with the problem of mixed H 2 /H ∞ control for an offshore floating wind turbine system. Firstly, we consider the modeling of a wind turbine system with collective pitch control scheme and the interaction with drive train dynamics and tower motions. The scenario is for the above rated wind speed conditions, where the goal is to keep the rotor rotational speed at its rated value while mitigating oscillations in the drive train and tower. Secondly, we present an effective technique to design a dynamic output-feedback mixed H 2 /H ∞ controller with pole placement constraints using a linear matrix inequality (LMI) approach. Pole placement constraints are implemented in order to improve the closed loop system response. Finally, a model obtained from the wind turbine simulation software FAST is used to illustrate the effectiveness of the proposed design technique.
In this paper by applying the Quantized space and time theory, the speed limit of protons has been determined and consequently the Lorentz factor has been calculated with a high degree of accuracy. Eventually the mass equivalent to energy of Higgs boson which is created by collision of two proton beams (This experiment has been performed in LHC) has been calculated precisely to .
An exponential H8 synchronization method is addressed for a class of uncertain master and slave neural networks with mixed time-delays, where the mixed delays comprise different neutral, discrete and distributed time-delays. An appropriate discretized Lyapunov-Krasovskii functional and some free weighting matrices are utilized to establish some delay-dependent sufficient conditions for designing a delayed state-feedback control as a synchronization law in terms of linear matrix inequalities under less restrictive conditions. The controller guarantees the exponential H8 synchronization of the two coupled master and slave neural networks regardless of their initial states. Numerical simulations are provided to demonstrate the effectiveness of the established synchronization laws.
Mobile receiver complexity persists as one of the key areas of concern in the adoption of MIMO technologies for systems such as high-speed downlink packet access (HSDPA) in UMTS. This is particularly the case for high-order modulation schemes such as 16-QAM and 64-QAM, where optimum a posteriori probability (APP) detection becomes too complex, and sub-optimal detection based on serial or parallel interference cancellation performs poorly. The above issues are successfully tackled by introducing a judicious layered encoding process at the transmitter, which once appropriately exploited at the receiver, allows considerable reductions in computational complexity in addition to improvements in performance.
Industry 5.0 aims to prioritize human operators, focusing on their well-being and capabilities, while promoting collaboration between humans and robots to enhance efficiency and productivity. The integration of collaborative robots must ensure the health and well-being of human operators. Indeed, this paper addresses the need for a human-centered framework proposing a preference-based optimization algorithm in a human–robot collaboration (HRC) scenario with an ergonomics assessment to improve working conditions. The HRC application consists of optimizing a collaborative robot end-effector pose during an object-handling task. The following approach (AmPL-RULA) utilizes an Active multi-Preference Learning (AmPL) algorithm, a preference-based optimization method, where the user is requested to iteratively provide qualitative feedback by expressing pairwise preferences between a couple of candidates. To address physical well-being, an ergonomic performance index, Rapid Upper Limb Assessment (RULA), is combined with the user's pairwise preferences, so that the optimal setting can be computed. Experimental tests have been conducted to validate the method, involving collaborative assembly during the object handling performed by the robot. Results illustrate that the proposed method can improve the physical workload of the operator while easing the collaborative task.
Co-segmentation aims at segmenting common objects from a group of images. Markov random field (MRF) has been widely used to solve co-segmentation, which introduces a global constraint to make the foreground similar to each other. However, it is difficult to minimize the new model. In this paper, we propose a new Markov random field-based co-segmentation model to solve co-segmentation problem without minimization problem. In our model, foreground similarity constraint is added into the unary term of MRF model rather than the global term, which can be minimized by graph cut method. In the model, a new energy function is designed by considering both the foreground similarity and the background consistency. Then, a mutual optimization approach is used to minimize the energy function. We test the proposed method on many pairs of images. The experimental results demonstrate the effectiveness of the proposed method.
The problem of coordinated control for multiple marine vessels in the presence of external disturbances is considered in this paper. A robust coordinated control algorithm is proposed for multiple marine vessels. The proposed robust coordinated control algorithm is divided into two parts. The first part develops an extended state observer to estimate the disturbances of marine vessels. The second part presents a robust coordinated control algorithm based on the output of the extended state observer. Furthermore, the robust coordinated control algorithm is designed using the dynamic surface control method. In light of the leader-follower strategy, the trajectory for each vessel is defined according to the desired trajectory of the assigned leader and the relative distance with respect to the leader. The effectiveness of the proposed coordination algorithm is demonstrated by the simulation results.
A novel iris biometric watermarking scheme is proposed focusing on iris recognition instead of the traditional watermark for increasing the security of the digital products. The preprocess of iris image is to be done firstly, which generates the iris biometric template from person's eye images. And then the templates are to be on discrete cosine transform; the value of the discrete cosine is encoded to BCH error control coding. The host image is divided into four areas equally correspondingly. The BCH codes are embedded in the singular values of each host image's coefficients which are obtained through discrete cosine transform (DCT). Numerical results reveal that proposed method can extract the watermark effectively and illustrate its security and robustness.
Small wind turbines are becoming an attractive solution for household applications. These micro generation units can be used as standalone applications or grid connected applications. However to get the full potential benefits of these wind turbines, systems should be low cost and reliable. Introducing the wind speed and rotor speed sensors at the generator shaft may reduce the reliability of small wind turbines. In this study, a grid connected sensor-less 5 kW small wind energy conversion system has been studied. The maximum power point tracking method of the wind turbine is totally independent from wind speed and rotor speed measurements. Optimum rotor speed and actual rotor speed are estimated using output current and voltage of the generator. To estimate the optimum rotor speed of the wind turbine, power signal feedback method has been used. Moreover, a sliding-mode observer is designed to estimate the rotor speed. Performance of the sliding-mode observer system has been compared with the measured rotor speed based wind energy conversion system. The simulation results show the effectiveness of the proposed sensor-less control system for the system under consideration.
In this paper, intelligent devices in industrial manufacturing are modeled as the nodes in the network systems. The sampled-data control is adopted to guarantee the synchronization of the network systems. The proposed sampled-data control strategy can reduce the updating frequency of the controller and the network communication burden. The closed-loop system is equivalently rewritten as the feedback interaction of a linear time-invariant system and a time-delay operator. The small gain theorem is utilized to calculate the upper bound of the sampling intervals. Furthermore, the integral quadratic constraints can provide the passivity-type property of the operator and give less-conservative results. Moreover, in order to further use the information about the sampling pattern and sawtooth structure, the time-delay integral operator is replaced by sample-data integral operator, and less-conservative results are proposed. Finally, the effectiveness of the proposed sampled-data distributed control strategy is demonstrated by a numerical example.
A mixed H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">infin</sub> control design methodology is presented for second-order neutral linear systems with time-varying state and input delays. Delay-dependent sufficient conditions for the design of a desired control are given in terms of LMIs. A controller, which guarantees asymptotic stability and a mixed H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">infin</sub> performance for the closed-loop system of the second-order neutral linear system, is then developed directly instead of coupling the model to a first-order neutral system based on a Lyapunov-Krasovskii method. A numerical example with simulation results illustrates the effectiveness of the proposed methodology.
Nowadays, each newly produced car must conform to the appropriate safety standards and norms. The most direct way to observe how a car behaves during a collision and to assess its crashworthiness is to perform a crash test. Because of the fact that vehicle crash tests are complex and complicated experiments it is advisable to establish their mathematical models. This paper contains an overview of the kinematic and dynamic relationships of a vehicle in a collision. There is also presented basic mathematical model representing a collision together with its analysis. The main part of this paper is devoted to methods of establishing parameters of the vehicle crash model and to real crash data investigation i.e. - creation of a Kelvin model for a real experiment, its analysis and validation. After model's parameters extraction a quick assessment of an occupant crash severity is done.
