1,212 research outputs found
Effect of Voltage Sag on an Induction Motor
No full textThe aim of this paper is to analyze the performance of the three phase squirrel cage induction motor under various voltage fluctuation levels. Generally, Induction motor drives are preferred for its simple and easy control. Their performance depends on relative power supply quality such as voltage sag, harmonics, voltage unbalance and voltage fluctuations. The induction motor is more sensitive to voltage fluctuations within certain amplitude levels and frequencies. This paper presents a study of voltage sag effects on an induction motor using simulation. In this paper, the impact of voltage fluctuations on induction motor performance is investigated. S. Sakthivel "Effect of Voltage Sag on an Induction Motor" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-2 | Issue-5 , August 2018, URL: https://www.ijtsrd.com/papers/ijtsrd18298.pd
Output tracking control design with anti-disturbance rejection for modified repetitive nonlinear control systems
No full textThis paper intends to analyse the disturbance rejection and output tracking control for a class of nonlinear control systems with disturbances. In this connection, we present a method that combines a proportional-integral observer and nonlinear-equivalent-input-disturbance estimator for superior disturbance rejection performance. Specifically, the nonlinear-equivalent-input-disturbance estimator comprises of equivalent-input-disturbance estimator and nonlinear feedback term, which is employed to estimate and reject the disturbances from the nonlinear system. Notably, the proportional-integral loop in the proportional-integral observer reduces the estimation inaccuracy of the nonlinear-equivalent-input-disturbance. Then the estimated disturbance is intertwined into the repetitive control input to compensate it efficiently. In order to obtain the required results, the proposed control system is converted into a two-dimensional modified repetitive control system to describe the learning and control actions. In particular, the proposed controller enables to adjust the gains directly to improve the learning and control performance and as a result, the tracking accuracy increases. Using a general Lyapunov–Krasovskii functional, singular value decomposition technique and linear matrix inequalities approach, a design algorithm for establishing proportional-integral observer and feedback gains is developed for the system under consideration. Finally, simulation results are given to illustrate the developed method's validity and superiority
Output Tracking Control for Fractional-Order Positive Switched Systems with Input Time Delay
No full textThe objective of this brief is to focus on the problem of output tracking control for a class of fractional-order positive switched systems via an observer-based controller method that combines equivalent-input-disturbance approach and Smith predictor. By employing Lyapunov theory together with average dwell-time approach, a new exponential stability criterion is derived in terms of linear matrix inequalities for the resulting closed-loop system. Based on the derived delay-dependent criterion, a design method of the proposed controller is then presented. The designed controller can assure that the output signals of the system trace the specified reference signals within the preferred neighborhood of the equilibrium. Furthermore, the solvability inclusive conditions for the proposed controller design of the considered system are established according to the state being available or not. Numerical simulation results are provided to demonstrate the strong disturbance rejection capability and the superiority of the proposed control design method over some existing ones
sj-docx-1-pie-10.1177_09544089231207476 - Supplemental material for Can pretrained networks be used in fault diagnosis of monoblock centrifugal pump?
No full textSupplemental material, sj-docx-1-pie-10.1177_09544089231207476 for Can pretrained networks be used in fault diagnosis of monoblock centrifugal pump? by Arun Balaji M, Naveen Venkatesh S, Sakthivel N R and Sugumaran V in Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering</p
A Robust Repetitive-Control Design for a Class of Uncertain Stochastic Dynamical Systems
No full textIn this brief, we study the problem of output tracking for continuous-time stochastic dynamical systems with parametric uncertainties and aperiodic disturbances by using a modified repetitive controller (MRC). More precisely, the MRC is obtained based on the equivalent input disturbance (EID) technique such that the closed-loop modified repetitive-control system is asymptotically stable in the presence of uncertainties and aperiodic disturbances. The main advantage of the proposed controller is that it can incorporate an EID estimator, which estimates and eliminates disturbances in the repetitive-control systems. Finally, simulation is conducted to reveal that the proposed controller can effectively reject the aperiodic disturbance, reduce the stochastic noise, and track the reference signal without steady-state error
Dissipative based adaptive reliable sampled-data control of time-varying delay systems
No full textThis paper is concerned with the problem of dissipative based adaptive reliable controller for a class of time delay systems subject to actuator failures and time-varying sampling with a known upper bound on the sampling intervals. By constructing a proper Lyapunov-Krasovskii functional which fully uses the available information about the actual sampling pattern and time delays, a new set of sufficient conditions is derived to obtain the required result. Then, a dissipative based adaptive sampled-data controller is designed such that the resulting closed-loop system is reliable in the sense that it is asymptotically stable and has the prescribed dissipative performance under given constraints. The existence condition of the desired dissipative based adaptive reliable sampled-data controller is obtained in terms of linear matrix inequalities. Further, the performance of the proposed controller is implemented on a liquid propellant rocket motor with a pressure feeding system model. The simulation results show the effectiveness and better performance of the proposed adaptive reliable sampled-data controller over conventional reliable controller
EID estimator-based modified repetitive control for singular systems with time-varying delay
No full textThis paper investigates the disturbance rejection for a modified repetitive control system (MRCS) that is described by a class of linear singular systems in the presence of external disturbances and time-varying delay. In particular, an equivalent-input-disturbance (EID)-based estimator is included in the MRCS to compensate both periodic and aperiodic disturbances which yields an EID-based MRCS. More precisely, the incorporation of the EID-based estimator into the control input enables rejection of all types of disturbances in MRCS and tracking of a periodic reference input is archived via a repetitive controller. Attention is focused on the state-feedback repetitive controller design which not only guarantees the regular, impulse free, and asymptotic stability of the closed-loop singular MRCS, but also provides an optimized upper bound of the time-varying delay. Based on Lyapunov stability theory and utilizing some advanced mathematical techniques, a new set of delay-dependent sufficient conditions is presented in terms of linear matrix inequalities for obtaining the required result. Then, an explicit expression for the desired state-feedback repetitive control law is developed. Further, the obtained results are validated through two numerical examples in the simulation section
Co-stimulatory molecules : genes to protein in autoimmune and inflammatory disorders
No full textCo‐stimulatory molecules are antigen‐independent generators of secondary signals which aid in maintaining the homeostasis of the immune system. The most extensively studied co‐stimulatory pathway is CD28/CTLA‐4, expressed on the T cells, interacting with CD80/CD86, expressed on the antigen presenting cells (APC). The interaction between CD28 and CD80/CD86 initiates the activation of T cells, whereas subsequent interaction between CTLA‐4 and CD80/CD86 inhibits the activated T lymphocytes. Also, there exist several other co‐stimulatory pathways. The co‐stimulatory molecules analyzed, in this study are B7H3, CD28, CD80, CD86, CTLA‐4, PD‐1, PD‐L1 and PD‐L2.This study involves both with genetic associations and protein expression of co‐stimulatory molecules (either stimulatory or inhibitory) in case‐control and population‐based studies. In the case‐control study, we categorized two types of model diseases: 1) the B‐cell induced autoantibody mediated disease, myasthenia gravis (MG) and 2) the T‐cell mediated inflammatory diseases, abdominal aortic aneurysm (AAA). In the population based study, we have selected subjects aged above 70 in the county of Uppsala, Sweden.At the genetic level, the key role of inhibitory receptors, B7H3 and Programmed Death‐1 (PD‐1), were evaluated in MG. No significant differences in genotype frequencies or allele frequencies in MG patients when compared with controls were found. The study, with PD‐ 1, was extended at mRNA and protein expression levels. Though we could not demonstrate any significant differences at mRNA levels, there was an increased expression of PD‐1 and PD‐L1 on T cells and monocytes, respectively. This demonstrates the existence regulatory mechanism behind MG.The soluble (s) forms of co‐stimulatory molecules sCD28, sCD80, sCD86, sCTLA‐4 were evaluated in patients with AAA and in general population. We could demonstrate increased circulating levels of soluble forms of CD28, CD86 and decreased levels of soluble forms of CTLA‐4 among AAA patients when compared with controls. In the general population, levels of soluble forms of co‐stimulatory molecules were positively related to pro‐inflammatory cytokines such as TNF‐α, IL‐6, IL‐1α, IL‐1β, IFN‐γ and chemokines such as IL‐8, but inversely related to CC chemokine, MCP‐1. We could not demonstrate any direct relation of soluble co‐stimulatory molecules to adhesion molecules and other atherosclerotic factors. The detection of soluble forms of PD‐1 could be demonstrated neither in the patients with MG nor in the controls.In conclusion, we suggest that the co‐stimulatory molecules have a significant impact on the status of the immune activation behind the two types of disorders. Therefore, we suggest that sCD28, sCD80, sCD86, sCTLA‐4 could be used as biomarkers for evaluating the process of inflammation. Furthermore, our study suggests a natural regulation of MG through the interaction between PD‐1/PD‐L1.List of scientific papersI. Sakthivel P, Wang X, Gharizadeh B, Giscombe R, Pirskanen R, Nyren P, Lefvert AK (2006). Single-nucleotide polymorphisms in the B7H3 gene are not associated with human autoimmune myasthenia gravis. J Genet. 85(3): 217-20. https://pubmed.ncbi.nlm.nih.gov/17406098 II. Sakthivel P, Shively V, Kakoulidou M, Pearce W, Lefvert AK (2007). The soluble forms of CD28, CD86 and CTLA-4 constitute possible immunological markers in patients with abdominal aortic aneurysm. J Intern Med. 261(4): 399-407. https://pubmed.ncbi.nlm.nih.gov/17391115 III. Sakthivel P, Wermeling F, Gu M, Hulthe J, Elmgren A, Kakoulidou M, Lefvert AK. Lind L (2007). Soluble CD28, CD80, CD86 and CTLA ]4 are related to CRP and proinflammatory cytokines and chemokines in elderly Caucasians. [Submitted]IV. Sakthivel P, Ramanujam R, Wang XB, Pirskanen Matell, Lefvert AK (2007). Programmed Death ]1: from gene to protein in autoimmune human myasthenia gravis. Journal of Neuroimmunology. [Accepted] https://pubmed.ncbi.nlm.nih.gov/18037500 </p
Detection and Analysis of Lysozyme Activity in some Tuberous Plants and Calotropis Procera’s Latex
No full textTuber extract of all the plant species used in the study exhibited lysozyme activity confirming the ubiquitous presence of lysozyme in plants. Among the different plants screened for protein content the tuber extract of Solanum tuberosum showed highest buffer soluble protein while tuber extract of Raphanus sativus showed the lowest protein content in sodium acetate buffer (50 Mm; pH 5.0). Tuber extract of Raphanus sativus showed highest lysozyme activity among all the plant species tested in this study and the activity was increased when the tuber was extracted with sodium phosphate buffer (50mM; pH 7.0). The lowest lysozyme was observed with tuber extract of Daucus carota in phosphate buffer (50mM; pH 7.0). The latex of the tropical species Calotropis procera is well known for being a rich source of the lysozyme. Lysozyme of Calotropis procera latex is not thermo labile. It did not lose much of its activity when the latex was incubated at different temperatures for 24 hours. A positive pointer for purification of this enzyme in future. Calotropis procera lysozyme can be was specifically isolated and purified from the whole latex with ammonium sulphate precipitation with 95% saturation. Calotropis procera lysozyme retained its activity even after precipitation with ammonium sulphate and dialysis and could hydrolyse the cell wall of Micrococcus lysodeikticus.Key words: Micrococcus lysodeikticus, Tuberous Plants, Latex, Ammonium sulphate precipitation, Polyacrylamide gel electrophoresis M. Sakthivel et al. Detection and Analysis of Lysozyme Activity in some Tuberous Plants and Calotropis Procera’s Latex. J Phytol 2/11 (2010) 65-72
High performance and thermally stable tandem solar selective absorber coating for concentrated solar thermal power (CSP) application
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