Hafiz Ahsan Ahmed - Academia.edu (original) (raw)

Papers by Hafiz Ahsan Ahmed

Research paper thumbnail of Enhanced Quasi Type-1 PLL-Based Multi-Functional Control of Single-Phase Dynamic Voltage Restorer

Applied Sciences, 2021

This paper considers the reference signal generation problem for the multi-functional operation o... more This paper considers the reference signal generation problem for the multi-functional operation of single-phase dynamic voltage restorers. For this purpose, a single-phase quasi type-1 phase-locked loop (QT1-PLL) is proposed. The pre-loop filter part of this PLL is composed of a frequency-fixed delayed signal cancellation method and a two-stage all-pass filter. Thanks to the frequency-fixed nature, the pre-loop filter is easy to implement and can provide rejection of any measurement offset. Moreover, this PLL benefits from the excellent harmonic robustness property of the conventional QT1-PLL. Small-signal modeling and gain tuning procedures are detailed in this paper. In order to track the reference voltage signals generated by the proposed PLL, a super-twisting sliding mode controller is also presented, which helps to achieve fast dynamic responses. Laboratory-scale prototype-based experimental studies were conducted to validate the developed reference generator and the controller...

Research paper thumbnail of Robust Gradient Estimator for Unknown Frequency Estimation in Noisy Environment: Application to Grid-Synchronization

IEEE Access, 2020

This work was supported by the U.K. Biotechnology and Biological Sciences Research Council throug... more This work was supported by the U.K. Biotechnology and Biological Sciences Research Council through the Magnetic and Wireless Sensor Technology for improving profit, biosecurity and carbon footprint of regional oyster production (NOSy) under Grant BB/S004203/1. Data availability: The datasets and models generated during the current study are available from the corresponding author on reasonable request.

Research paper thumbnail of Integration of Large-Scale Electric Vehicles into Utility Grid: An Efficient Approach for Impact Analysis and Power Quality Assessment

Sustainability, 2021

Electric vehicles (EVs) have received massive consideration in the automotive industries due to t... more Electric vehicles (EVs) have received massive consideration in the automotive industries due to their improved performance, efficiency and capability to minimize global warming and carbon emission impacts. The utilization of EVs has several potential benefits, such as increased use of renewable energy, less dependency on fossil-fuel-based power generations and energy-storage capability. Although EVs can significantly mitigate global carbon emissions, it is challenging to maintain power balance during charging on-peak hours. Thus, it mandates a comprehensive impact analysis of high-level electric vehicle penetration in utility grids. This paper investigates the impacts of large-scale EV penetration on low voltage distribution, considering the charging time, charging method and characteristics. Several charging scenarios are considered for EVs’ integration into the utility grid regarding power demand, voltage profile, power quality and system adequacy. A lookup-table-based charging ap...

Research paper thumbnail of Differential neural network identifier with composite learning laws for uncertain nonlinear systems

IFAC-PapersOnLine, 2020

This manuscript describes the design and numerical implementation of a novel composite differenti... more This manuscript describes the design and numerical implementation of a novel composite differential neural network aimed to estimate nonlinear uncertain systems. A differential neural network (DNN) with a composite feedback matrix approximates the structure of non-linear uncertain systems. The feedback matrix is assumed to belong to a convex set as well as the free parameters of the DNN (weights) at any instant of time. Therefore, l-different DNN works in parallel. A composite Lyapunov function finds the convex hull approximation of the set of DNN working together to improve the approximation capabilities of classical neural networks. The main result of this study shows the practical stability of the estimation error. Numerical simulations demonstrate the approximation capabilities of the composite DNN implemented in a Van Der Pol oscillator where the presence of high-frequency components makes difficult a classical DNN approximation.

Research paper thumbnail of Second-order sliding-mode differentiators: an experimental comparative analysis using Van der Pol oscillator

International Journal of Control, 2018

This document is the author's post-print version, incorporating any revisions agreed during the p... more This document is the author's post-print version, incorporating any revisions agreed during the peer-review process. Some differences between the published version and this version may remain and you are advised to consult the published version if you wish to cite from it.

Research paper thumbnail of Adaptive Filtering-Based Pseudo Open-Loop Three-Phase Grid-Synchronization Technique

Energies, 2020

This paper studies the grid-synchronization problem of three-phase system. Second-order adaptive ... more This paper studies the grid-synchronization problem of three-phase system. Second-order adaptive filters are a popular tool for grid-synchronization. In this context, reduced-order generalized integrator has attracted some attention in recent time. However, existing implementations cannot control directly the closed-loop poles (real and imaginary) of reduced-order generalized integrator. To overcome this limitation, this paper proposes a novel reduced-order generalized integrator structure. To make the proposed technique frequency adaptive, an open-loop frequency estimation technique is also used. Comparative performance analysis are provided over two other advanced and recently proposed techniques. Results demonstrate the suitability and effectiveness of the proposed technique.

Research paper thumbnail of Gradient Estimator-Based Amplitude Estimation for Dynamic Mode Atomic Force Microscopy: Small-Signal Modeling and Tuning

Sensors, 2020

Atomic force microscopy (AFM) plays an important role in nanoscale imaging application. AFM works... more Atomic force microscopy (AFM) plays an important role in nanoscale imaging application. AFM works by oscillating a microcantilever on the surface of the sample being scanned. In this process, estimating the amplitude of the cantilever deflection signal plays an important role in characterizing the topography of the surface. Existing approaches on this topic either have slow dynamic response e.g., lock-in-amplifier or high computational complexity e.g., Kalman filter. In this context, gradient estimator can be considered as a trade-off between fast dynamic response and high computational complexity. However, no constructive tuning rule is available in the literature for gradient estimator. In this paper, we consider small-signal modeling and tuning of gradient estimator. The proposed approach greatly simplifies the tuning procedure. Numerical simulation and experimental results are provided to demonstrate the suitability of the proposed tuning procedure.

Research paper thumbnail of Output Global Oscillatory Synchronization of Heterogeneous Systems

International Journal of Control, 2019

The global output synchronization problem for heterogeneous nonlinear systems having relative deg... more The global output synchronization problem for heterogeneous nonlinear systems having relative degree 2 or higher is studied. The proposed approach consists in two steps. First, a partial projection of individual subsystems into the Brockett oscillators is performed using a sliding-mode control. Second, the network of these oscillators is synchronized using the global synchronization results of a particular second order nonlinear oscillator model from Ahmed et al. (2019). Our approach is based on output feedback and uses a higher order sliding mode observer to estimate the states and perturbations of the synchronized nonlinear systems. Along with numerical simulations, the performance of the proposed synchronization scheme is experimentally verified on a network of Van der Pol oscillators.

Research paper thumbnail of Robust global synchronization of Brockett oscillators

IEEE Transactions on Control of Network Systems, 2018

In this article, motivated by a recent work of R. Brockett [1], a robust global synchronization p... more In this article, motivated by a recent work of R. Brockett [1], a robust global synchronization problem of multistable Brockett oscillators has been studied within an Input-to-State Stability (ISS) framework. Following a recent generalization of the classical ISS theory to multistable systems and its application to the synchronization of multistable systems, two synchronization protocols are designed with respect to compact invariant sets of the unperturbed Brockett oscillator. The conditions obtained in our work are global and applicable to families of non-identical oscillators in contrast to the local analysis of [1]. Numerical simulation examples illustrate our theoretical results.

Research paper thumbnail of Monitoring Biological Rhythms Through the Dynamic Model Identification of an Oyster Population

IEEE Transactions on Systems, Man, and Cybernetics: Systems, 2017

The measurements of valve activity in a population of bivalves under natural environmental condit... more The measurements of valve activity in a population of bivalves under natural environmental conditions (16 oysters in the Bay of Arcachon, France) are used for a physiological model identification. A nonlinear auto-regressive exogenous (NARX) model is designed and tested. The method to design the model has two parts. 1) Structure of the model: The model takes into account the influence of environmental conditions using measurements of the sunlight intensity, the moonlight, tide levels, precipitation and water salinity levels. A possible influence of the internal circadian/circatidal clocks is also analyzed. 2) Least square calculation of the model parameters. Through this study, it is demonstrated that the developed dynamical model of the oyster valve movement can be used for estimating normal physiological rhythms of permanently immersed oysters and can be considered for detecting perturbations of these rhythms due to changes in the water quality, i.e. for ecological monitoring.

Research paper thumbnail of On conditions of robust synchronization for multistable systems

2015 European Control Conference (ECC), 2015

This paper deals with a robust synchronization problem for multistable systems evolving on manifo... more This paper deals with a robust synchronization problem for multistable systems evolving on manifolds in the context of Input-to-State Stability (ISS) framework. Based on a recent generalization of classical ISS theory to multistable systems (may have unstable equilibrium), a robust synchronization protocol is designed with respect to a compact invariant set of the unperturbed system. The invariant set is assumed to admit a decomposition without cycles (basically no homoclinic nor heteroclinic orbits may exist). Numerical simulation examples illustrate our theoretical results.

Research paper thumbnail of Automatic spawning detection in oysters: a fault detection approach

2015 European Control Conference (ECC), 2015

Using measurements of valve activity in a population of bivalves under natural environmental cond... more Using measurements of valve activity in a population of bivalves under natural environmental condition (16 oysters in the Bay of Arcachon, France), an algorithm for the automatic detection of spawning period of oysters is proposed. The algorithm is based on the fault detection approach and it works through the estimation of velocity of valves movement activity, which can be obtained by calculating the time derivative of the valves distance. A summarized description on the method used for the derivative estimation is provided, followed by the associated signal processing and decision making algorithm to determine spawning from the velocity signal. A protection from false spawning detection is also considered by analyzing the synchronicity in spawning. Through this study, it is shown that spawning in a population of oysters living in their natural habitat (i.e. in the sea) can be automatically detected without any human expertise, like visual analysis.

Research paper thumbnail of Velocity estimation of valve movement in oysters for water quality surveillance

IFAC-PapersOnLine, 2015

The measurements of valve opening activity in a population of oysters under natural environmental... more The measurements of valve opening activity in a population of oysters under natural environmental conditions are used to estimate the velocity of their valve movement activity. Three different differentiation schemes were used to estimate the velocity, namely an algebraicbased differentiator method, a non-homogeneous higher order sliding mode differentiator and a homogeneous finite-time differentiator. The estimated velocities were then used to compare the performances of these three different differentiators. We demonstrate that this estimated velocity can be used for water quality monitoring as the differentiators can detect very rapid change in valve movements of the oyster population resulting from some external stimulus or common input.

Research paper thumbnail of Robust Synchronization for Multistable Systems

IEEE Transactions on Automatic Control, 2016

In this note, we study a robust synchronization problem for multistable systems evolving on manif... more In this note, we study a robust synchronization problem for multistable systems evolving on manifolds within an Input-to-State Stability (ISS) framework. Based on a recent generalization of the classical ISS theory to multistable systems, a robust synchronization protocol is designed with respect to a compact invariant set of the unperturbed system. The invariant set is assumed to admit a decomposition without cycles, that is, with neither homoclinic nor heteroclinic orbits. Numerical simulation examples illustrate our theoretical results.

Research paper thumbnail of Dynamical model identification of population of oysters for water quality monitoring

2014 European Control Conference (ECC), 2014

The measurements of valve activity in a population of bivalves under natural environmental condit... more The measurements of valve activity in a population of bivalves under natural environmental conditions (16 oysters in the Bay of Arcachon, France) are used for a physiological model identification. A nonlinear auto-regressive exogenous (NARX) model is designed and tested. The model takes into account the influence of environmental conditions using measurements of the sunlight intensity, the moonlight and tide levels. A possible influence of the internal circadian/circatidal clocks is also analyzed. Through this application, it is demonstrated that the developed dynamical model can be used for estimation of the normal physiological rhythms of permanently immersed oysters and considered for detection of perturbations of these rhythms due to changes in the water quality, i.e. for ecological monitoring.

Research paper thumbnail of Design of permanent magnet synchronous machines of direct-driven generator with Emetor and FLUX 2D

2012 IEEE Business, Engineering & Industrial Applications Colloquium (BEIAC), 2012

The research for optimization tool of electrical machine has developed for decades. Permanent Mag... more The research for optimization tool of electrical machine has developed for decades. Permanent Magnet is a new addition in this arena. This paper describes the design of a direct-driven generator designed with Emetor and Flux 2D. The initial analytical design is done with Emetor. Then the experimented result is verified with a FEM (Finite Element Method) simulation software from Cedrat

Research paper thumbnail of Simplified Second-Order Generalized Integrator - Frequency-Locked Loop

Advances in Electrical and Electronic Engineering, 2019

Second-Order Generalized Integrator-Frequency-Locked Loop (SOGI-FLL) is a popular technique avail... more Second-Order Generalized Integrator-Frequency-Locked Loop (SOGI-FLL) is a popular technique available in the grid synchronization literature. This technique uses gain normalization in the frequency locked-loop. This increases the computational complexity. In this paper, we propose an alternative implementation to reduce the computational complexity of the SOGI-FLL. The proposed implementation modifies mainly the frequency locked-loop part and requires normalized voltage measurement. dSPACE 1104 boardbased hardware implementation shows that the proposed implementation executes 20 % faster than the standard implementation. This could be very beneficial for high switching frequency application e.g. ≥ 1 MHz. In addition to the nominal frequency case, multi-resonant implementation is also proposed to tackle grid harmonics using a simpler harmonic decoupling network. Small signal dynamical modeling and tuning are performed for both implementations. Dynamical equivalence is also established between the two implementations. Experimental comparative analysis demonstrates similar or better performance (depending on test scenarios) with respect to the standard implementation of the SOGI-FLL.

Research paper thumbnail of A framework of artificial light management for optimal plant development for smart greenhouse application

PLOS ONE

Smart greenhouse farming has emerged as one of the solutions to global food security, where farmi... more Smart greenhouse farming has emerged as one of the solutions to global food security, where farming productivity can be managed and improved in an automated manner. While it is known that plant development is highly dependent on the quantity and quality of light exposure, the specific impact of the different light properties is yet to be fully understood. In this study, using the model plant Arabidopsis, we systematically investigate how six different light properties (i.e., photoperiod, light offset, intensity, phase of dawn, duration of twilight and period) would affect plant development i.e., flowering time and hypocotyl (seedling stem) elongation using an established mathematical model of the plant circadian system relating light input to flowering time and hypocotyl elongation outputs for smart greenhouse application. We vary each of the light properties individually and then collectively to understand their effect on plant development. Our analyses show in comparison to the no...

Research paper thumbnail of Accuracy evaluation of hand-eye calibration techniques for vision-guided robots

PLOS ONE

Hand-eye calibration is an important step in controlling a vision-guided robot in applications li... more Hand-eye calibration is an important step in controlling a vision-guided robot in applications like part assembly, bin picking and inspection operations etc. Many methods for estimating hand-eye transformations have been proposed in literature with varying degrees of complexity and accuracy. However, the success of a vision-guided application is highly impacted by the accuracy the hand-eye calibration of the vision system with the robot. The level of this accuracy depends on several factors such as rotation and translation noise, rotation and translation motion range that must be considered during calibration. Previous studies and benchmarking of the proposed algorithms have largely been focused on the combined effect of rotation and translation noise. This study provides insight on the impact of rotation and translation noise acting in isolation on the hand-eye calibration accuracy. This deviates from the most common method of assessing hand-eye calibration accuracy based on pose n...

Research paper thumbnail of Fundamental frequency sequence amplitude estimator for power and energy applications

PLOS ONE

A grid-synchronization-based fundamental frequency positive-sequence (FFPS) and negative-sequence... more A grid-synchronization-based fundamental frequency positive-sequence (FFPS) and negative-sequence (FFNS) amplitudes estimation technique is proposed for unbalanced and distorted grid. In this technique, the sequence amplitudes are extracted by extracting the phase-angle of the FFPS and FFNS components. The extracted phase-angles have DC and double frequency AC components. The AC component is filtered out by using a Moving Average Filter (MAF) of appropriate window length. From the extracted phase-angle, the unknown frequency can be estimated by using a suitable controller. A frequency-fixed equidistant samples-based pre-loop filter is also applied to eliminate the effect of measurement offset. The proposed technique has a very simple structure and is easy to tune. Small-signal modeling-based stability analysis and gain tuning procedure are also provided. The proposed technique strikes a good balance between fast convergence and disturbance rejection capability. Comparative numerical...

Research paper thumbnail of Enhanced Quasi Type-1 PLL-Based Multi-Functional Control of Single-Phase Dynamic Voltage Restorer

Applied Sciences, 2021

This paper considers the reference signal generation problem for the multi-functional operation o... more This paper considers the reference signal generation problem for the multi-functional operation of single-phase dynamic voltage restorers. For this purpose, a single-phase quasi type-1 phase-locked loop (QT1-PLL) is proposed. The pre-loop filter part of this PLL is composed of a frequency-fixed delayed signal cancellation method and a two-stage all-pass filter. Thanks to the frequency-fixed nature, the pre-loop filter is easy to implement and can provide rejection of any measurement offset. Moreover, this PLL benefits from the excellent harmonic robustness property of the conventional QT1-PLL. Small-signal modeling and gain tuning procedures are detailed in this paper. In order to track the reference voltage signals generated by the proposed PLL, a super-twisting sliding mode controller is also presented, which helps to achieve fast dynamic responses. Laboratory-scale prototype-based experimental studies were conducted to validate the developed reference generator and the controller...

Research paper thumbnail of Robust Gradient Estimator for Unknown Frequency Estimation in Noisy Environment: Application to Grid-Synchronization

IEEE Access, 2020

This work was supported by the U.K. Biotechnology and Biological Sciences Research Council throug... more This work was supported by the U.K. Biotechnology and Biological Sciences Research Council through the Magnetic and Wireless Sensor Technology for improving profit, biosecurity and carbon footprint of regional oyster production (NOSy) under Grant BB/S004203/1. Data availability: The datasets and models generated during the current study are available from the corresponding author on reasonable request.

Research paper thumbnail of Integration of Large-Scale Electric Vehicles into Utility Grid: An Efficient Approach for Impact Analysis and Power Quality Assessment

Sustainability, 2021

Electric vehicles (EVs) have received massive consideration in the automotive industries due to t... more Electric vehicles (EVs) have received massive consideration in the automotive industries due to their improved performance, efficiency and capability to minimize global warming and carbon emission impacts. The utilization of EVs has several potential benefits, such as increased use of renewable energy, less dependency on fossil-fuel-based power generations and energy-storage capability. Although EVs can significantly mitigate global carbon emissions, it is challenging to maintain power balance during charging on-peak hours. Thus, it mandates a comprehensive impact analysis of high-level electric vehicle penetration in utility grids. This paper investigates the impacts of large-scale EV penetration on low voltage distribution, considering the charging time, charging method and characteristics. Several charging scenarios are considered for EVs’ integration into the utility grid regarding power demand, voltage profile, power quality and system adequacy. A lookup-table-based charging ap...

Research paper thumbnail of Differential neural network identifier with composite learning laws for uncertain nonlinear systems

IFAC-PapersOnLine, 2020

This manuscript describes the design and numerical implementation of a novel composite differenti... more This manuscript describes the design and numerical implementation of a novel composite differential neural network aimed to estimate nonlinear uncertain systems. A differential neural network (DNN) with a composite feedback matrix approximates the structure of non-linear uncertain systems. The feedback matrix is assumed to belong to a convex set as well as the free parameters of the DNN (weights) at any instant of time. Therefore, l-different DNN works in parallel. A composite Lyapunov function finds the convex hull approximation of the set of DNN working together to improve the approximation capabilities of classical neural networks. The main result of this study shows the practical stability of the estimation error. Numerical simulations demonstrate the approximation capabilities of the composite DNN implemented in a Van Der Pol oscillator where the presence of high-frequency components makes difficult a classical DNN approximation.

Research paper thumbnail of Second-order sliding-mode differentiators: an experimental comparative analysis using Van der Pol oscillator

International Journal of Control, 2018

This document is the author's post-print version, incorporating any revisions agreed during the p... more This document is the author's post-print version, incorporating any revisions agreed during the peer-review process. Some differences between the published version and this version may remain and you are advised to consult the published version if you wish to cite from it.

Research paper thumbnail of Adaptive Filtering-Based Pseudo Open-Loop Three-Phase Grid-Synchronization Technique

Energies, 2020

This paper studies the grid-synchronization problem of three-phase system. Second-order adaptive ... more This paper studies the grid-synchronization problem of three-phase system. Second-order adaptive filters are a popular tool for grid-synchronization. In this context, reduced-order generalized integrator has attracted some attention in recent time. However, existing implementations cannot control directly the closed-loop poles (real and imaginary) of reduced-order generalized integrator. To overcome this limitation, this paper proposes a novel reduced-order generalized integrator structure. To make the proposed technique frequency adaptive, an open-loop frequency estimation technique is also used. Comparative performance analysis are provided over two other advanced and recently proposed techniques. Results demonstrate the suitability and effectiveness of the proposed technique.

Research paper thumbnail of Gradient Estimator-Based Amplitude Estimation for Dynamic Mode Atomic Force Microscopy: Small-Signal Modeling and Tuning

Sensors, 2020

Atomic force microscopy (AFM) plays an important role in nanoscale imaging application. AFM works... more Atomic force microscopy (AFM) plays an important role in nanoscale imaging application. AFM works by oscillating a microcantilever on the surface of the sample being scanned. In this process, estimating the amplitude of the cantilever deflection signal plays an important role in characterizing the topography of the surface. Existing approaches on this topic either have slow dynamic response e.g., lock-in-amplifier or high computational complexity e.g., Kalman filter. In this context, gradient estimator can be considered as a trade-off between fast dynamic response and high computational complexity. However, no constructive tuning rule is available in the literature for gradient estimator. In this paper, we consider small-signal modeling and tuning of gradient estimator. The proposed approach greatly simplifies the tuning procedure. Numerical simulation and experimental results are provided to demonstrate the suitability of the proposed tuning procedure.

Research paper thumbnail of Output Global Oscillatory Synchronization of Heterogeneous Systems

International Journal of Control, 2019

The global output synchronization problem for heterogeneous nonlinear systems having relative deg... more The global output synchronization problem for heterogeneous nonlinear systems having relative degree 2 or higher is studied. The proposed approach consists in two steps. First, a partial projection of individual subsystems into the Brockett oscillators is performed using a sliding-mode control. Second, the network of these oscillators is synchronized using the global synchronization results of a particular second order nonlinear oscillator model from Ahmed et al. (2019). Our approach is based on output feedback and uses a higher order sliding mode observer to estimate the states and perturbations of the synchronized nonlinear systems. Along with numerical simulations, the performance of the proposed synchronization scheme is experimentally verified on a network of Van der Pol oscillators.

Research paper thumbnail of Robust global synchronization of Brockett oscillators

IEEE Transactions on Control of Network Systems, 2018

In this article, motivated by a recent work of R. Brockett [1], a robust global synchronization p... more In this article, motivated by a recent work of R. Brockett [1], a robust global synchronization problem of multistable Brockett oscillators has been studied within an Input-to-State Stability (ISS) framework. Following a recent generalization of the classical ISS theory to multistable systems and its application to the synchronization of multistable systems, two synchronization protocols are designed with respect to compact invariant sets of the unperturbed Brockett oscillator. The conditions obtained in our work are global and applicable to families of non-identical oscillators in contrast to the local analysis of [1]. Numerical simulation examples illustrate our theoretical results.

Research paper thumbnail of Monitoring Biological Rhythms Through the Dynamic Model Identification of an Oyster Population

IEEE Transactions on Systems, Man, and Cybernetics: Systems, 2017

The measurements of valve activity in a population of bivalves under natural environmental condit... more The measurements of valve activity in a population of bivalves under natural environmental conditions (16 oysters in the Bay of Arcachon, France) are used for a physiological model identification. A nonlinear auto-regressive exogenous (NARX) model is designed and tested. The method to design the model has two parts. 1) Structure of the model: The model takes into account the influence of environmental conditions using measurements of the sunlight intensity, the moonlight, tide levels, precipitation and water salinity levels. A possible influence of the internal circadian/circatidal clocks is also analyzed. 2) Least square calculation of the model parameters. Through this study, it is demonstrated that the developed dynamical model of the oyster valve movement can be used for estimating normal physiological rhythms of permanently immersed oysters and can be considered for detecting perturbations of these rhythms due to changes in the water quality, i.e. for ecological monitoring.

Research paper thumbnail of On conditions of robust synchronization for multistable systems

2015 European Control Conference (ECC), 2015

This paper deals with a robust synchronization problem for multistable systems evolving on manifo... more This paper deals with a robust synchronization problem for multistable systems evolving on manifolds in the context of Input-to-State Stability (ISS) framework. Based on a recent generalization of classical ISS theory to multistable systems (may have unstable equilibrium), a robust synchronization protocol is designed with respect to a compact invariant set of the unperturbed system. The invariant set is assumed to admit a decomposition without cycles (basically no homoclinic nor heteroclinic orbits may exist). Numerical simulation examples illustrate our theoretical results.

Research paper thumbnail of Automatic spawning detection in oysters: a fault detection approach

2015 European Control Conference (ECC), 2015

Using measurements of valve activity in a population of bivalves under natural environmental cond... more Using measurements of valve activity in a population of bivalves under natural environmental condition (16 oysters in the Bay of Arcachon, France), an algorithm for the automatic detection of spawning period of oysters is proposed. The algorithm is based on the fault detection approach and it works through the estimation of velocity of valves movement activity, which can be obtained by calculating the time derivative of the valves distance. A summarized description on the method used for the derivative estimation is provided, followed by the associated signal processing and decision making algorithm to determine spawning from the velocity signal. A protection from false spawning detection is also considered by analyzing the synchronicity in spawning. Through this study, it is shown that spawning in a population of oysters living in their natural habitat (i.e. in the sea) can be automatically detected without any human expertise, like visual analysis.

Research paper thumbnail of Velocity estimation of valve movement in oysters for water quality surveillance

IFAC-PapersOnLine, 2015

The measurements of valve opening activity in a population of oysters under natural environmental... more The measurements of valve opening activity in a population of oysters under natural environmental conditions are used to estimate the velocity of their valve movement activity. Three different differentiation schemes were used to estimate the velocity, namely an algebraicbased differentiator method, a non-homogeneous higher order sliding mode differentiator and a homogeneous finite-time differentiator. The estimated velocities were then used to compare the performances of these three different differentiators. We demonstrate that this estimated velocity can be used for water quality monitoring as the differentiators can detect very rapid change in valve movements of the oyster population resulting from some external stimulus or common input.

Research paper thumbnail of Robust Synchronization for Multistable Systems

IEEE Transactions on Automatic Control, 2016

In this note, we study a robust synchronization problem for multistable systems evolving on manif... more In this note, we study a robust synchronization problem for multistable systems evolving on manifolds within an Input-to-State Stability (ISS) framework. Based on a recent generalization of the classical ISS theory to multistable systems, a robust synchronization protocol is designed with respect to a compact invariant set of the unperturbed system. The invariant set is assumed to admit a decomposition without cycles, that is, with neither homoclinic nor heteroclinic orbits. Numerical simulation examples illustrate our theoretical results.

Research paper thumbnail of Dynamical model identification of population of oysters for water quality monitoring

2014 European Control Conference (ECC), 2014

The measurements of valve activity in a population of bivalves under natural environmental condit... more The measurements of valve activity in a population of bivalves under natural environmental conditions (16 oysters in the Bay of Arcachon, France) are used for a physiological model identification. A nonlinear auto-regressive exogenous (NARX) model is designed and tested. The model takes into account the influence of environmental conditions using measurements of the sunlight intensity, the moonlight and tide levels. A possible influence of the internal circadian/circatidal clocks is also analyzed. Through this application, it is demonstrated that the developed dynamical model can be used for estimation of the normal physiological rhythms of permanently immersed oysters and considered for detection of perturbations of these rhythms due to changes in the water quality, i.e. for ecological monitoring.

Research paper thumbnail of Design of permanent magnet synchronous machines of direct-driven generator with Emetor and FLUX 2D

2012 IEEE Business, Engineering & Industrial Applications Colloquium (BEIAC), 2012

The research for optimization tool of electrical machine has developed for decades. Permanent Mag... more The research for optimization tool of electrical machine has developed for decades. Permanent Magnet is a new addition in this arena. This paper describes the design of a direct-driven generator designed with Emetor and Flux 2D. The initial analytical design is done with Emetor. Then the experimented result is verified with a FEM (Finite Element Method) simulation software from Cedrat

Research paper thumbnail of Simplified Second-Order Generalized Integrator - Frequency-Locked Loop

Advances in Electrical and Electronic Engineering, 2019

Second-Order Generalized Integrator-Frequency-Locked Loop (SOGI-FLL) is a popular technique avail... more Second-Order Generalized Integrator-Frequency-Locked Loop (SOGI-FLL) is a popular technique available in the grid synchronization literature. This technique uses gain normalization in the frequency locked-loop. This increases the computational complexity. In this paper, we propose an alternative implementation to reduce the computational complexity of the SOGI-FLL. The proposed implementation modifies mainly the frequency locked-loop part and requires normalized voltage measurement. dSPACE 1104 boardbased hardware implementation shows that the proposed implementation executes 20 % faster than the standard implementation. This could be very beneficial for high switching frequency application e.g. ≥ 1 MHz. In addition to the nominal frequency case, multi-resonant implementation is also proposed to tackle grid harmonics using a simpler harmonic decoupling network. Small signal dynamical modeling and tuning are performed for both implementations. Dynamical equivalence is also established between the two implementations. Experimental comparative analysis demonstrates similar or better performance (depending on test scenarios) with respect to the standard implementation of the SOGI-FLL.

Research paper thumbnail of A framework of artificial light management for optimal plant development for smart greenhouse application

PLOS ONE

Smart greenhouse farming has emerged as one of the solutions to global food security, where farmi... more Smart greenhouse farming has emerged as one of the solutions to global food security, where farming productivity can be managed and improved in an automated manner. While it is known that plant development is highly dependent on the quantity and quality of light exposure, the specific impact of the different light properties is yet to be fully understood. In this study, using the model plant Arabidopsis, we systematically investigate how six different light properties (i.e., photoperiod, light offset, intensity, phase of dawn, duration of twilight and period) would affect plant development i.e., flowering time and hypocotyl (seedling stem) elongation using an established mathematical model of the plant circadian system relating light input to flowering time and hypocotyl elongation outputs for smart greenhouse application. We vary each of the light properties individually and then collectively to understand their effect on plant development. Our analyses show in comparison to the no...

Research paper thumbnail of Accuracy evaluation of hand-eye calibration techniques for vision-guided robots

PLOS ONE

Hand-eye calibration is an important step in controlling a vision-guided robot in applications li... more Hand-eye calibration is an important step in controlling a vision-guided robot in applications like part assembly, bin picking and inspection operations etc. Many methods for estimating hand-eye transformations have been proposed in literature with varying degrees of complexity and accuracy. However, the success of a vision-guided application is highly impacted by the accuracy the hand-eye calibration of the vision system with the robot. The level of this accuracy depends on several factors such as rotation and translation noise, rotation and translation motion range that must be considered during calibration. Previous studies and benchmarking of the proposed algorithms have largely been focused on the combined effect of rotation and translation noise. This study provides insight on the impact of rotation and translation noise acting in isolation on the hand-eye calibration accuracy. This deviates from the most common method of assessing hand-eye calibration accuracy based on pose n...

Research paper thumbnail of Fundamental frequency sequence amplitude estimator for power and energy applications

PLOS ONE

A grid-synchronization-based fundamental frequency positive-sequence (FFPS) and negative-sequence... more A grid-synchronization-based fundamental frequency positive-sequence (FFPS) and negative-sequence (FFNS) amplitudes estimation technique is proposed for unbalanced and distorted grid. In this technique, the sequence amplitudes are extracted by extracting the phase-angle of the FFPS and FFNS components. The extracted phase-angles have DC and double frequency AC components. The AC component is filtered out by using a Moving Average Filter (MAF) of appropriate window length. From the extracted phase-angle, the unknown frequency can be estimated by using a suitable controller. A frequency-fixed equidistant samples-based pre-loop filter is also applied to eliminate the effect of measurement offset. The proposed technique has a very simple structure and is easy to tune. Small-signal modeling-based stability analysis and gain tuning procedure are also provided. The proposed technique strikes a good balance between fast convergence and disturbance rejection capability. Comparative numerical...