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ABSTRACT: A novel controller based on the decoupling of single-ended primary inductor converter (SEPIC) state-space averaging model to four simple first-order systems is proposed. Instead of designing a single controller for a fourth-order SEPIC converter, four PI controllers are designed for the four decoupled systems. Combining the four PI controllers with the four decoupled systems forms a multi-loop feedback control system which is able to work at a wider operating condition. Circuit implementation of the proposed controller is presented and experimental results are included to demonstrate the effectiveness of the proposed design scheme.
IET Power Electronics 10/2011; · 1.62 Impact Factor
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ABSTRACT: We investigate the chaotic phase synchronization in a system of coupled bursting neurons in small-world networks. A transition to mutual phase synchronization takes place on the bursting time scale of coupled oscillators, while on the spiking time scale, they behave asynchronously. It is shown that phase synchronization is largely facilitated by a large fraction of shortcuts, but saturates when it exceeds a critical value. We also study the external chaotic phase synchronization of bursting oscillators in the small-world network by a periodic driving signal applied to a single neuron. It is demonstrated that there exists an optimal small-world topology, resulting in the largest peak value of frequency locking interval in the parameter plane, where bursting synchronization is maintained, even with the external driving. The width of this interval increases with the driving amplitude, but decrease rapidly with the network size. We infer that the externally applied driving parameters outside the frequency locking region can effectively suppress pathologically synchronized rhythms of bursting neurons in the brain.
Chaos (Woodbury, N.Y.) 03/2011; 21(1):013127. · 1.80 Impact Factor
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ABSTRACT: Power spectral analysis is a traditional method used for EEG analysing. In this paper, Welch method was used to process the signals obtained from a carefully designed acupuncture experiment. The main objective of this work is to find the effect of acupuncture on brain. A protocol composed of three different manipulations has been designed to acquire the EEG signals using 22 biosensors. Totally 9 healthy volunteers with an age group of 23-27 years old have been used in this acupuncture experiment and ANOVA test was adopt to reveal the differences among several acupuncture stages. At last, an apparent phenomenon was found in the study.
Automation and Logistics (ICAL), 2010 IEEE International Conference on; 09/2010
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ABSTRACT: A simple equivalent series inductance (ESL) and equivalent series resistance (ESR) measurement technique for capacitors is presented. A low-cost square waveform voltage source coupled with a reference resistor can be used to measure the ESL, ESR and capacitance of an electrolytic capacitor. By connecting a capacitor in series with a reference resistor, the equivalent output step response of the capacitor voltage reveals the ESL and ESR of the capacitor. To effectively capture the output step response, a square input waveform is used instead. The square waveform voltage source can easily be realised using a DC voltage source and simple switching devices. Experimental results are included to demonstrate the effectiveness of the proposed scheme.
IET Power Electronics 08/2010; · 1.62 Impact Factor
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ABSTRACT: We consider the assumption of existence of the general nonlinear internal model that is introduced in the design of robust output regulators for a class of minimum-phase nonlinear systems with rth degree (r ≥ 2). The robust output regulation problem can be converted into a robust stabilisation problem of an augmented system consisting of the given plant and a high-gain nonlinear internal model, perfectly reproducing the bounded including not only periodic but also nonperiodic exogenous signal from a nonlinear system, which satisfies some general immersion assumption. The state feedback controller is designed to guarantee the asymptotic convergence of system errors to zero manifold. Furthermore, the proposed scheme makes use of output feedback dynamic controller that only processes information from the regulated output error by using high-gain observer to robustly estimate the derivatives of the regulated output error. The stabilisation analysis of the resulting closed-loop systems leads to regional as well as semi-global robust output regulation achieved for some appointed initial condition in the state space, for all possible values of the uncertain parameter vector and the exogenous signal, ranging over an arbitrary compact set.
International Journal of Control 05/2010; 83(5):1009-1024. · 0.98 Impact Factor
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ABSTRACT: In this paper different topologies of populations of FitzHugh-Nagumo neurons have been introduce to investigate the effect of high-frequency driving on the response of neuron populations to a subthreshold low-frequency signal. We show that optimal amplitude of high-frequency driving enhances the response of neuron populations to a subthreshold low-frequency input and the optimal amplitude dependences on the connection among the neurons. By analyzing several kinds of topology (i.e., random and small world) different behaviors have been observed. Several topologies behave in an optimal way with respect to the range of low-frequency amplitude leading to an improvement in the stimulus response coherence, while others with respect to the maximum values of the performance index. However, the best results in terms of both the suitable amplitude of high-frequency driving and high stimulus response coherence have been obtained when the neurons have been connected in a small-world topology.
Chaos (Woodbury, N.Y.) 03/2010; 20(1):013113. · 1.80 Impact Factor
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Neurocomputing. 01/2010; 74:230-238.
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ABSTRACT: A simple equivalent series resistance (ESR) measurement technique for capacitors at high current and high frequency is presented. A low-cost square waveform voltage source coupled with a reference resistor can be used to measure the ESR of an electrolytic capacitor. By connecting a capacitor in series with a reference resistor, the ratio of the voltage magnitude across the capacitor to the voltage magnitude of the supply voltage reveals the ESR of the capacitor if the frequency of the supply source is sufficiently high. The square waveform voltage source can easily be realised using a DC voltage source and simple switching devices. An addition of a small inductor in series with the reference resistor could eliminate the effect of the equivalent series inductance and improve the measurement accuracy. A mathematical analysis is presented to demonstrate that the use of the square waveform and the addition of the small inductor are valid. Experimental results are included to demonstrate the effectiveness of the proposed scheme.
IET Power Electronics 10/2009; · 1.62 Impact Factor
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ABSTRACT: An internal model control with conditional integrator is proposed for the robust output regulation of single-switch quadratic buck converters. The output regulation problem of a quadratic buck converter is converted to the stabilisation of an augmented system consisting of the buck converter and the internal model. The design procedures include the design of an internal model with conditional integrator and a robust state feedback stabiliser with saturation behaviour. The closed-loop stability of the converter will be theoretically analysed. Finally, the effectiveness of the proposed control scheme for large load and supply variations are also tested. The design of the controller does not require the exact circuit parameters and the stability proof demonstrates the robustness against parameter uncertainties.
IET Power Electronics 10/2009; · 1.62 Impact Factor
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ABSTRACT: Intermodulation and harmonics are important in frequency analysis of nonlinear systems. In neuron research, most investigations are taken in studying synchronization between the external stimuli and the output of neuron, but harmonics and intermodulation are often ignored. In this paper, harmonics and intermodulation of the subthreshold FitzHugh-Nagumo neuron are investigated and their magnitudes are used to predict frequency response of the neuron. Furthermore, through analyzing the magnitudes of harmonics, the intrinsic frequencies of the neuron could be identified.
Chaos (Woodbury, N.Y.) 09/2009; 19(3):033144. · 1.80 Impact Factor
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Electric Power Components and Systems 03/2009; 37(3):320-330. · 0.68 Impact Factor
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ABSTRACT: An internal model control using a conditional integrator compensator is proposed for the robust output regulation of a DC/DC buck converter. Based on the input-output linearisation from the state-space averaged model of the DC/DC buck converter, the robust output regulation problem of this type of converter can be converted into a robust stabilisation problem of an augmented system consisting of the given buck converter and the internal model by introducing a proper internal model. Another advantage of the proposed method is to sense the capacitor current instead of the inductor current. The effectiveness of the proposed converter is verified by comparing the proposed controller performance with single-loop PI control and double-loop PI control under load disturbances and supply voltage variations.
Electronics Letters 02/2008; · 0.96 Impact Factor
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ABSTRACT: A simple, fast detection scheme for voltage dip and voltage swell is presented. Applying a simple relay and lowpass filter to the supply voltage signal, an in-phase fixed magnitude reference signal with very low total harmonic distortion can be generated. Comparing the supply signal with the in-phased fixed magnitude reference sinusoid, any change of magnitude in the supply signal can be detected. The detection scheme can indicate voltage dip and voltage swell in less than a quarter of the cycle of oscillation. Experimental results are presented to demonstrate the effectiveness of the proposed detection scheme
Electronics Letters 02/2007; · 0.96 Impact Factor
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ABSTRACT: A very-low-cost active power filter with power-factor-correction capability for solving power quality problem is proposed. Model-based cascade controller design is presented for the control of the shunt active filter. Harmonic reductions and power-factor correction will both be carried out by the proposed filter. Discussions on the design of the current and voltage control loops are given. Circuit implementation of the proposed control scheme is presented and experimental results are included to demonstrate the effectiveness of the proposed design scheme
IEE Proceedings - Electric Power Applications 10/2006; · 0.55 Impact Factor
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ABSTRACT: A search algorithm for the identification of multiple inputs nonlinear systems using the orthogonal least squares estimator is derived. Because of the high dimensionality of general nonlinear systems the forward regression algorithm is used to detect the plausible size of the final fitted model and a variation of the forward regression algorithm is proposed. Instead of choosing the best candidate term at each iteration, top few candidate terms which have the largest error reduction ratios are investigated at each iteration. A search algorithm coupled with the model predicted output is derived which will sort through all plausible candidate terms to produce an optimal solution for the problem. Simulated and experimental examples are included to demonstrate the effectiveness of the proposed algorithm.
Electrical Engineering 05/2006; 88(5):357-365. · 0.40 Impact Factor
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Electric Power Components and Systems 10/2005; 33(10):1137-1143. · 0.68 Impact Factor
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Electric Power Components and Systems 09/2005; 33(9):973-983. · 0.68 Impact Factor
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ABSTRACT: In order to deal with the increasing demand for good load and supply-voltage regulation of DC/DC convertors, a new cascade controller is proposed. The control of DC/DC buck convertor is first decomposed into a primary voltage-control loop and a secondary current-control loop. The cascade controller is then implemented based on the buck-converter settings with the dynamics of the secondary loop much faster than these of the primary loop. A robustness analysis of the cascade controller against load changes and supply changes is presented. Experimental results are included to demonstrate the effectiveness of the proposed control scheme over a conventional single-loop PI controller. The proposed controller can be implemented as a low-cost addon to a conventional single-loop controller. Detail design equations are presented.
IEE Proceedings - Electric Power Applications 08/2005; · 0.55 Impact Factor
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ABSTRACT: PID controllers have been very successful in industrial applications. However, for nonlinear processes, their performances are not very satisfactory. Conventional active power factor correction (PFC) converters use classical PI controllers to carry out output voltage regulation and power factor correction. Since the process is highly nonlinear, an adaptive controller has been developed to improve the performance of PFC converters. An orthogonal least squares estimation algorithm was incorporated for the identification of boost converters. A parsimonious nonlinear model for power converters was obtained based on the output prediction and the error reduction ratio test. The least mean squares algorithm is then implemented for the online tracking of the system parameters and the adaptive controller was derived based on the fitted model. Experimental studies were carried out to demonstrate the effectiveness of the proposed identification and control algorithm for power factor correction and harmonic elimination.
IEE Proceedings - Electric Power Applications 06/2005; · 0.55 Impact Factor
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ABSTRACT: Nonlinear systems are decomposed into slow and fast response subsystems using the singular perturbation theory and second-order sliding mode controllers are designed for each of the subsystems. The combined control action forms a suboptimal controller that can eliminate chattering in the continuous control output. Simulated examples are included to demonstrate the effectiveness of the proposed algorithm.
ISA Transactions 02/2005; 44(1):117-29. · 1.11 Impact Factor
