Showing papers by "Hamid Reza Karimi published in 2009"

Fault detection for discrete-time Markov jump linear systems with partially known transition probabilities

Abstract: In this article, the fault detection (FD) problem for a class of discrete-time Markov jump linear system (MJLS) with partially known transition probabilities is investigated. The proposed systems are more general, which relax the traditional assumption in Markov jump systems that all the transition probabilities must be completely known. A residual generator is constructed and the corresponding FD is formulated as an H ∞ filtering problem by which the error between residual and fault are minimised in the H ∞ sense. The linear matrix inequality-based sufficient conditions for the existence of FD filter are derived. A numerical example on a multiplier–accelerator model economic system is given to illustrate the potential of the developed theoretical results.

Robust H 1 Filter Design for Uncertain Linear Systems Over Network with Network-Induced Delays and Output Quantization

Abstract: This paper investigates a convex optimization approach to the problem of robustH1 ltering for uncertain linear systems connected over a common digital communication network. We consider the case where quantizers are static and the parameter uncertainties are norm bounded. Firstly, we propose a new model to investigate the eect of both the output quantization levels and the network conditions. Secondly, by introducing a descriptor technique, using Lyapunov-Krasovskii functional and a suitable change of variables, new required sucient conditions are established in terms of delay-dependent linear matrix inequalities (LMIs) for the existence of the desired network-based quantized lters with simultaneous consideration of network induced delays and measurement quantization. The explicit expression of the lters is derived to satisfy both asymptotic stability and a prescribed level of disturbance attenuation for all admissible norm bounded uncertainties.

Morphological diversity of Pistacia species in Iran

Abstract: Pistachio is one of the most important horticultural crops in Iran. Selection of suitable genotypes, resistant to unfavorable environmental and soil conditions and diseases, are important for increasing yield efficiency and the acreage of this important crop. The aim of this research was to evaluate wild pistachio species and genotypes native to Iran and also to determine any relationships that exist according to their phenotypical characteristics. A total of 11 pistachio types in situ from Kerman and Fars provinces and ex situ from the Iranian Pistachio Research Institute (IPRI) were used during the research. Thirty-one morphological characteristics (17 quantitative and 14 qualitative) were evaluated based on the pistachio descriptor (IPGRI). Results from simple correlation analyses showed significant positive and negative correlations in certain important characteristics. Nut thickness and weight were in significant correlation with the size (dimensions) of the leaves and terminal leaflets. Factor analysis was used to determine the effective characteristics and the number of main factors. For each factor loading a value of more than 0.65 was judged as being significant. Effective characteristics were categorized into seven main factors that contributed to 94% of the overall variance. Leaf and nut characteristics were defined mainly by the first factor contributing to 40% of the total variance. Pistachio genotypes were clustered based on seven factors and at a similarity distance of 10, these were further divided into three sub-clusters each consisting of genotypes belonging to species P. vera L., P. khinjuk Stocks. and P. atlantica Desf. Based on the results, P.khinjuk was located between the other two species, but resembled P. atlantica more than P. vera.

Semiactive Backstepping Control for Vibration Reduction in a Structure with Magnetorheological Damper Subject to Seismic Motions

Abstract: The use of magnetorheological (MR) dampers for mitigating vibrations caused by seismic motions in civil engineering structures has attracted much interest in the scientific community because of the advantages of this class of device. It is known that MR dampers can generate high damping forces with low energy requirements and low cost of production. However, the complex dynamics that characterize MR dampers make difficult the control design for achieving the vibration reduction goals in an efficient manner. In this article, a semiactive controller based on the backstepping technique is proposed. The controller was applied to a three-story building with an MR damper at its first floor subjected to seismic motions. The performance of the controller was evaluated experimentally by means of real time hybrid testing.

LMI-based H∞ synchronization of second-order neutral master-slave systems using delayed output feedback control

Abstract: Submitted version of an article published in the journal: International Journal of Control, Automation and Systems. The original publication is available at www.springerlink.com: http://dx.doi.org/10.1007/s12555-009-0306-5

Frequency domain control based on quantitative feedback theory for vibration suppression in structures equipped with magnetorheological dampers

Abstract: This paper addresses the problem of designing quantitative feedback theory (QFT) based controllers for the vibration reduction in a structure equipped with an MR damper. In this way, the controller is designed in the frequency domain and the natural frequencies of the structure can be directly accounted for in the process. Though the QFT methodology was originally conceived of for linear time invariant systems, it can be extended to nonlinear systems. A new methodology is proposed for characterizing the nonlinear hysteretic behavior of the MR damper through the uncertainty template in the Nichols chart. The resulting controller performance is evaluated in a real-time hybrid testing experiment.

Genetic relationships among Pistacia species using AFLP markers

Abstract: This study addresses the phylogenetic relationship between Pistacia species by amplified fragment length polymorphism (AFLP). The plant materials of this study consisted of a total of 44 accessions belonging to P. vera, P. eurycarpa, P. khinjuk, all subspecies of P. atlantica (atlantica, mutica, kurdica and cabulica), three unknown genotypes and three accessions, proposed to be hybrid from P. eurycarpa × P. atlantica. The accessions were from Iran, Turkey, USA and Syria. Six AFLP primer combinations produced a total of 475 fragments, with average of 79.16 fragments per primer pair, of which, 336 bands were polymorphic. Unweighted pair group method based on arithmetic average (UPGMA) analysis was performed on jaccard’s similarity coefficient matrix and also average similarity of each species. According to the results, two main clusters were developed and P. vera, P. eurycarpa, P. atlantica (subsp. atlantica, kurdica, mutica, cabulica) and the hybrid genotypes located in the first main cluster. P. khinjuk accessions from Iran and USA localized in second main cluster. The hybrid accessions located between eurycarpa and atlantica species and their hybrid nature between these two species were confirmed. One of the unknown accessions clustered with the hybrid ones and the two other were grouped closely with P. Khinjuk. According to this study, the closest species to P. vera was Eurycarpa group, followed by P. atlantica. UPGMA analysis separated P. atlantica subsp. mutica and cabulica from P. atlantica and P. eurycarpa. Subspecies mutica and cabulica were two closest genotypes; hence, P. atlantica subsp. mutica could be classified as a distinct species as P. mutica and the cabulica as a subspecies of P. mutica. This study revealed that P. eurycarpa is synonym for P. atlantica subsp. kurdica and should be considered distinct from P. atlantica; however, P. atlantica showed a closer genetic similarity to P. eurycarpa than the other species.

Energy-Efficient Cluster-Based Scheme for Handling Node Failure in Real-Time Sensor Networks

Abstract: Wireless sensor networks are characterized by dense deployment of energy constrained nodes. Owing to the deployment of large number of sensor nodes in uncontrolled hostile or harsh environments and unmonitored operation, it is common that a node becomes inactive due to a node failure or exhaustion of the respective energy resource. Such node failures result in the reduction of the cluster quality of service (Qos). This problem becomes more complex when the services in the wireless sensor network (WSN) are real-time. To avoid the degradation of QoS, it is necessary that the failures be recovered using a proper method. In this paper, we present a dynamic energy efficient real-time job allocation algorithm called ERTJA for handling such node failures in a cluster. ERTJA relies on the other cluster nodes to handle the node failure. It tries to minimize the energy consumption of the cluster by minimal activation of the sleeping nodes, while guaranteeing the QoS of the cluster application. Further, when the number of sleeping nodes is limited, the proposed algorithm uses the idle times of the existing nodes to have a graceful QoS degradation of the cluster QoS upon the node failure. Simulation results show significant performance improvements of ERTJA in terms of energy consumption comparing to the N-EDF-Plus algorithm. According to the results, ERTJA can save up to 27.2% of the cluster energy consumption with respect to N-EDF-Plus.

A mixed H 2 /H ∞ -based semiactive control for vibration mitigation in flexible structures

Abstract: In this paper, we address this problem through the design of a semiactive controller based on the mixed H 2 /H ∞ control theory. The vibrations caused by the seismic motions are mitigated by a semiactive damper installed in the bottom of the structure. It is meant by semiactive damper, a device that absorbs but cannot inject energy into the system. Sufficient conditions for the design of a desired control are given in terms of linear matrix inequalities (LMIs). A controller that guarantees asymptotic stability and a mixed H 2 /H ∞ performance is then developed. An algorithm is proposed to handle the semiactive nature of the actuator. The performance of the controller is experimentally evaluated in a real-time hybrid testing facility that consists of a physical specimen (a small-scale magnetorheological damper) and a numerical model (a large-scale three-story building).

Robust adaptive backstepping control design for a Nonlinear Hydraulic-Mechanical System

Abstract: The complex dynamics that characterize hydraulic systems make it difficult for the control design to achieve prescribed goals in an efficient manner. In this paper, we present the design and analysis of a robust nonlinear controller for a Nonlinear Hydraulic-Mechanical (NHM) System. The system consists of an electrohydraulic servo valve and two hydraulic cylinders. Specifically, by considering a part of the dynamics of the NHM system as a norm-bounded uncertainty, two adaptive controllers are developed based on the backstepping technique that ensure the tracking error signals asymptotically converge to zero despite the uncertainties in the system according to the Barbalat lemma. The resulting controllers are able to take into account the interval uncertainties in Coulomb friction parameters and in the internal leakage parameters in the cylinders. Two adaptation laws are obtained by using the Lyapunov functional method and inequality techniques. Simulation results demonstrate the performance and feasibility of the proposed method.

Stability analysis of neutral systems with mixed time-varying delays and nonlinear perturbations

Abstract: In this paper, the problem of stability analysis for a class of neutral systems with mixed time-varying neutral, discrete and distributed delays and nonlinear perturbations are addressed. By introducing a novel Lyapunov-Krasovskii functional and combining the descriptor model transformation, the Leibniz-Newton formula, some free weighting matrices and a suitable change of variables, new sufficient conditions are established for the stability of the considered system, which are neutral-delay-dependent, discrete-delay-range-dependent and distributed-delay-dependent. The conditions are presented in terms of linear matrix inequalities (LMIs) and can be easily solved by existing convex optimization techniques. A numerical example is given to demonstrate the less conservatism of the proposed results over some existence results in the literature.

Genetic Relationships of Some Pistacia Species Using RAPD and AFLP Markers

Abstract: Genetic diversity of plant species can be evaluated by various methods. The DNA markers are one of the most powerful techniques, because they are not affected by environmental factors as well as plant developmental stages. Markers such as RAPD, AFLP, RFLP and SSR are used for studying genetic diversity of plants. In order to corroborate our results and to minimize the experimental errors, in the present study, AFLP and RAPD markers were used. Genetic similarities (GS) were calculated for both markers using the Jaccard and Dice algorithms. Six AFLP primer combinations used in this study generated 475 scorable bands, of which 336 bands were polymorphic, while the 12 RAPD primers produced 130 bands, of which 118 showed polymorphism. Using Jaccard and Dice algorithms, correlation between the genetic similarity and cophenetic coefficient (CCC) for RAPD marker were 0.82 and 0.77, respectively. In the case of AFLP, CCC was 0.91 and 0.89, respectively. The highest CCCs were calculated with the Jaccard method.

Robust fault detection filter design for a class of linear systems with mixed time-varying delays and nonlinear perturbations

Abstract: In this note, the problem of robust fault detection filter (RFDF) design for a class of linear systems subjected to some nonlinear perturbations and mixed neutral and discrete time-varying delays is investigated based on an H ∞ performance condition. By introducing a descriptor technique, using Lyapunov-Krasovskii functional and a suitable change of variables, new required sufficient conditions are established in terms of delay-dependent linear matrix inequalities (LMIs) to synthesize the residual generation scheme. Based on Luenberger type observers, the explicit expression of the filters is derived for the fault such that both asymptotic stability and a prescribed level of disturbance attenuation are satisfied for all admissible nonlinear perturbations. A numerically example is provided to show performance of the proposed design approach.

On the Handling Node Failure: Energy-Efficient Job Allocation Algorithm for Real-Time Sensor Networks

Abstract: Wireless sensor networks are usually characterized by dense deployment of energy constrained nodes. Due to the usage of a large number of sensor nodes in uncontrolled hostile or harsh environments, node failure is a common event in these systems. Another common reason for node failure is the exhaustion of their energy resources and node inactivation. Such failures can have adverse effects on the quality of the real-time services in Wireless Sensor Networks (WSNs). To avoid such degradations, it is necessary that the failures be recovered in a proper manner to sustain network operation. In this paper we present a dynamic Energy efficient Real-Time Job Allocation (ERTJA) algorithm for handling node failures in a cluster of sensor nodes with the consideration of communication energy and time overheads besides the nodes' characteristics. ERTJA relies on the computation power of cluster members for handling a node failure. It also tries to minimize the energy consumption of the cluster by minimum activation of the sleeping nodes. The resulting system can then guarantee the Quality of Service (QoS) of the cluster application. Further, when the number of sleeping nodes is limited, the proposed algorithm uses the idle times of the active nodes to engage a graceful QoS degradation in the cluster. Simulation results show significant performance improvements of ERTJA in terms of the energy conservation and the probability of meeting deadlines compared with the other studied algorithms.

H∞ filter design for a class of nonlinear neutral systems with time-varying delays

Abstract: Accepted version of an article from the journal: Nonlinear Dynamics and Systems Theory. Also available from the publisher: http://www.e-ndst.kiev.ua/v9n3.htm