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Frédéric Rotella - One of the best experts on this subject based on the ideXlab platform.
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Performances comparison between ultra-Local Model control, integral iliding mode control and PID control for a coupled tanks system
International Journal of Modelling Identification and Control, 2018Co-Authors: Hajer Thabet, Mounir Ayadi, Frédéric RotellaAbstract:This paper deals with the comparison of robust control approaches for the level water control of coupled tanks system. A new ultra-Local Model control (ULMC) approach leading to adaptive controller is proposed. The parameter identification of the ultra-Local Model is based on the algebraic derivation techniques. The main advantages of this control strategy are its simplicity and robustness. A comparison study with the integral sliding mode control (ISMC) approach is carried out. The perfect knowledge of the output variable degree, which is a standard assumption for sliding modes, is assumed here. The comparison of the simulation results for the proposed adaptive controller with the ISMC controller and the classical PID controller has a better performances in the presence of external perturbations and parameter uncertainties.
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Design of adaptive PID controllers based on adaptive Smith predictor for ultra-Local Model control
International Journal of Automation and Control, 2017Co-Authors: Hajer Thabet, Mounir Ayadi, Frédéric RotellaAbstract:In this paper, an ultra-Local Model control approach based on adaptive Smith predictor is proposed. The design of adaptive PID controller takes into account the estimation of variable time delay which is compensated by the addition of an adaptive Smith predictor. The purpose of this paper is to solve the online estimation problem of time delay thanks to the proposed identification method of ultra-Local Model parameters. A performance comparison between the proposed control approach and the Smith predictor control with classical PID is carried out. The numerical simulation results of the thermal process study with severe constraints and operating conditions show the superiority of the adaptive PID controller. The robustness with respect to noises, disturbances and system parameter uncertainties of control approaches are highlighted.
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Towards an ultra-Local Model control of two-tank-system
International Journal of Dynamics and Control, 2016Co-Authors: Hajer Thabet, Mounir Ayadi, Frédéric RotellaAbstract:This paper deals with the design of an ultra-Local Model control. The proposed approach is based on the estimation of the ultra-Local Model parameters using least squares resolution technique instead of numerical derivation technique. The closed-loop control is implemented through an adaptive PI in order to reject the influences of the disturbance and noise output signals. Its main advantages are: its simplicity and its robustness with respect to the parameter uncertainties of system. In this paper, it is processed to test the efficiency of the parameter estimation method compared with the performance of numerical derivation technique. The method is applied to the water level control of a two-tank-system. Numerical simulations show that the generated desired trajectory is followed in an efficient way even with severe operating conditions.
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Experimental comparison of new adaptive PI controllers based on the ultra-Local Model parameter identification
International Journal of Control Automation and Systems, 2016Co-Authors: Hajer Thabet, Mounir Ayadi, Frédéric RotellaAbstract:This paper is devoted to an experimental comparison between two different methods of ultra-Local Model control. The concept of the first proposed technique is based on the linear system resolution technique to estimate the ultra-Local Model parameters. The second proposed method is based on the linear adaptive observer which allows the joint estimation of state and unknown system parameters. The closed-loop control is implemented via an adaptive PID controller. In order to show the efficiency of these two control strategies, experimental validations are carried out on a two-tank system. The experimental results show the effectiveness and robustness of the proposed controllers.
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An algebraic control approach based on the estimation of an ultra-Local Broïda Model
2015Co-Authors: Hajer Thabet, Mounir Ayadi, Frédéric RotellaAbstract:This paper deals with a new parameter estimation method for an ultra-Local Model of Broïda. The proposed approach is based on the algebraic derivation techniques and the linear system resolution method, in order to estimate the ultra-Local Model parameters, such that the variable time-delay. The closed-loop control is achieved via an adaptive PI controller to reject the influence of noises and disturbances. A simulation results of a thermal process application are given to validate the effectiveness of the proposed strategy. A performance comparison with a classical PID controller is achieved.
Benoît Goyeau - One of the best experts on this subject based on the ideXlab platform.
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Infiltration of a porous matrix by a solidifying liquid metal: A Local Model
International Journal of Thermal Sciences, 2017Co-Authors: Nadine Moussa, Dominique Gobin, Hervé Duval, Benoît GoyeauAbstract:This paper describes the first step of a study dedicated to the development of a macroscopic Model of casting of a metal foam by infiltration and solidification of a liquid metal in a porous mould. The first stage presented here describes a Local Model of injection of the metallic melt in a capillary tube and subsequent solidification of the metal by heat transfer to the duct walls. The Model is intended to account for the air/liquid interface displacement during the infiltration phase, for the heat transfer to the wall and for the growth of the solid phase in the presence of the fluid flow. The objective is to determine the influence of the operating conditions on the penetration depth and on the solidification time in a simplified geometry before using this Local information in a macroscopic homogenized Model presently under development.
Hajer Thabet - One of the best experts on this subject based on the ideXlab platform.
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Performances comparison between ultra-Local Model control, integral iliding mode control and PID control for a coupled tanks system
International Journal of Modelling Identification and Control, 2018Co-Authors: Hajer Thabet, Mounir Ayadi, Frédéric RotellaAbstract:This paper deals with the comparison of robust control approaches for the level water control of coupled tanks system. A new ultra-Local Model control (ULMC) approach leading to adaptive controller is proposed. The parameter identification of the ultra-Local Model is based on the algebraic derivation techniques. The main advantages of this control strategy are its simplicity and robustness. A comparison study with the integral sliding mode control (ISMC) approach is carried out. The perfect knowledge of the output variable degree, which is a standard assumption for sliding modes, is assumed here. The comparison of the simulation results for the proposed adaptive controller with the ISMC controller and the classical PID controller has a better performances in the presence of external perturbations and parameter uncertainties.
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Design of adaptive PID controllers based on adaptive Smith predictor for ultra-Local Model control
International Journal of Automation and Control, 2017Co-Authors: Hajer Thabet, Mounir Ayadi, Frédéric RotellaAbstract:In this paper, an ultra-Local Model control approach based on adaptive Smith predictor is proposed. The design of adaptive PID controller takes into account the estimation of variable time delay which is compensated by the addition of an adaptive Smith predictor. The purpose of this paper is to solve the online estimation problem of time delay thanks to the proposed identification method of ultra-Local Model parameters. A performance comparison between the proposed control approach and the Smith predictor control with classical PID is carried out. The numerical simulation results of the thermal process study with severe constraints and operating conditions show the superiority of the adaptive PID controller. The robustness with respect to noises, disturbances and system parameter uncertainties of control approaches are highlighted.
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Towards an ultra-Local Model control of two-tank-system
International Journal of Dynamics and Control, 2016Co-Authors: Hajer Thabet, Mounir Ayadi, Frédéric RotellaAbstract:This paper deals with the design of an ultra-Local Model control. The proposed approach is based on the estimation of the ultra-Local Model parameters using least squares resolution technique instead of numerical derivation technique. The closed-loop control is implemented through an adaptive PI in order to reject the influences of the disturbance and noise output signals. Its main advantages are: its simplicity and its robustness with respect to the parameter uncertainties of system. In this paper, it is processed to test the efficiency of the parameter estimation method compared with the performance of numerical derivation technique. The method is applied to the water level control of a two-tank-system. Numerical simulations show that the generated desired trajectory is followed in an efficient way even with severe operating conditions.
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Experimental comparison of new adaptive PI controllers based on the ultra-Local Model parameter identification
International Journal of Control Automation and Systems, 2016Co-Authors: Hajer Thabet, Mounir Ayadi, Frédéric RotellaAbstract:This paper is devoted to an experimental comparison between two different methods of ultra-Local Model control. The concept of the first proposed technique is based on the linear system resolution technique to estimate the ultra-Local Model parameters. The second proposed method is based on the linear adaptive observer which allows the joint estimation of state and unknown system parameters. The closed-loop control is implemented via an adaptive PID controller. In order to show the efficiency of these two control strategies, experimental validations are carried out on a two-tank system. The experimental results show the effectiveness and robustness of the proposed controllers.
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An algebraic control approach based on the estimation of an ultra-Local Broïda Model
2015Co-Authors: Hajer Thabet, Mounir Ayadi, Frédéric RotellaAbstract:This paper deals with a new parameter estimation method for an ultra-Local Model of Broïda. The proposed approach is based on the algebraic derivation techniques and the linear system resolution method, in order to estimate the ultra-Local Model parameters, such that the variable time-delay. The closed-loop control is achieved via an adaptive PI controller to reject the influence of noises and disturbances. A simulation results of a thermal process application are given to validate the effectiveness of the proposed strategy. A performance comparison with a classical PID controller is achieved.
Ali M Sadegh - One of the best experts on this subject based on the ideXlab platform.
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effect of trabecular architecture on transferring load impact to the brain a Local Model of single trabecula
ASME 2011 Summer Bioengineering Conference Parts A and B, 2011Co-Authors: Parisa Saboori, Ali M SadeghAbstract:In this paper the mechanotransduction of the external load through the trabeculae in the subarachnoid space (SAS) was investigated. This has been accomplished by employing the results of our animal studies, i.e. the histology and architecture of trabeculae, and by creating Local Models consist of a trabecula. It is concluded that the trabeculae are mainly configured as an upright tree-like shaped, where the branches are attached to the pia mater and the stems are attached to the arachnoid. The result of the analysis reveal that said configuration of the trabeculae creates less strain in the brain when the head in subjected to external loads, and thereby damps the impact.Copyright © 2011 by ASME
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Effect of Trabecular Architecture on Transferring Load/Impact to the Brain: A Local Model of Single Trabecula
ASME 2011 Summer Bioengineering Conference Parts A and B, 2011Co-Authors: Parisa Saboori, Ali M SadeghAbstract:In this paper the mechanotransduction of the external load through the trabeculae in the subarachnoid space (SAS) was investigated. This has been accomplished by employing the results of our animal studies, i.e. the histology and architecture of trabeculae, and by creating Local Models consist of a trabecula. It is concluded that the trabeculae are mainly configured as an upright tree-like shaped, where the branches are attached to the pia mater and the stems are attached to the arachnoid. The result of the analysis reveal that said configuration of the trabeculae creates less strain in the brain when the head in subjected to external loads, and thereby damps the impact.Copyright © 2011 by ASME
Seth Pettie - One of the best experts on this subject based on the ideXlab platform.
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an exponential separation between randomized and deterministic complexity in the Local Model
SIAM Journal on Computing, 2019Co-Authors: Yijun Chang, Tsvi Kopelowitz, Seth PettieAbstract:Over the past 30 years numerous algorithms have been designed for symmetry breaking problems in the Local Model, such as maximal matching, MIS, vertex coloring, and edge coloring. For most problems...
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a time hierarchy theorem for the Local Model
SIAM Journal on Computing, 2019Co-Authors: Yijun Chang, Seth PettieAbstract:The celebrated time hierarchy theorem for Turing machines states, informally, that more problems can be solved given more time. The extent to which a time hierarchy--type theorem holds in the class...
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a time hierarchy theorem for the Local Model
Foundations of Computer Science, 2017Co-Authors: Yijun Chang, Seth PettieAbstract:The celebrated Time Hierarchy Theorem for Turing machines states, informally, that more problems can be solved given more time. The extent to which a time hierarchy-type theorem holds in the classic distributed Local Model has been open for many years. In particular, it is consistent with previous results that all natural problems in the Local Model can be classified according to a small constant number of complexities, such as O(1), O(log* n), O(log n), 2^{O(sqrt{log n}), etc.In this paper we establish the first time hierarchy theorem for the Local Model and prove that several gaps exist in the Local time hierarchy. Our main results are as follows:• We define an infinite set of simple coloring problems called Hierarchical 2½-Coloring. A correctly colored graph can be confirmed by simply checking the neighborhood of each vertex, so this problem fits into the class of Locally checkable labeling (LCL) problems. However, the complexity of the k-level Hierarchical 2½-Coloring problem is Θ(n^{1/k}), for positive integer k. The upper and lower bounds hold for both general graphs and trees, and for both randomized and deterministic algorithms.• Consider any LCL problem on bounded degree trees. We prove an automatic-speedup theorem that states that any randomized n^{o(1)}-time algorithm solving the LCL can be transformed into a deterministic O(log n)-time algorithm. Together with a previous result, this establishes that on trees, there are no natural deterministic complexities in the ranges ω(log* n)—o(log n) or ω(log n)—n^{o(1)}.• We expose a gap in the randomized time hierarchy on general graphs. Roughly speaking, any randomized algorithm that solves an LCL problem in sublogarithmic time can be sped up to run in O(T_{LLL}) time, which is the complexity of the distributed Lovasz Local lemma problem, currently known to be Ω(log log n) and 2^{O(sqrt{log log n})} on bounded degree graphs.Finally, we revisit Naor and Stockmeyers characterization of O(1)-time Local algorithms for LCL problems (as order-invariant w.r.t. vertex IDs) and calculate the complexity gaps that are directly implied by their proof. For n-rings we see a ω(1)—o(log* n) complexity gap, for (sqrt{n} × √{n})-tori an ω(1)—o(sqrt{log* n}) gap, and for bounded degree trees and general graphs, an ω(1)—o(log(log* n)) complexity gap.
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a time hierarchy theorem for the Local Model
arXiv: Distributed Parallel and Cluster Computing, 2017Co-Authors: Yijun Chang, Seth PettieAbstract:The celebrated Time Hierarchy Theorem for Turing machines states, informally, that more problems can be solved given more time. The extent to which a time hierarchy-type theorem holds in the distributed Local Model has been open for many years. It is consistent with previous results that all natural problems in the Local Model can be classified according to a small constant number of complexities, such as $O(1),O(\log^* n), O(\log n), 2^{O(\sqrt{\log n})}$, etc. In this paper we establish the first time hierarchy theorem for the Local Model and prove that several gaps exist in the Local time hierarchy. 1. We define an infinite set of simple coloring problems called Hierarchical $2\frac{1}{2}$-Coloring}. A correctly colored graph can be confirmed by simply checking the neighborhood of each vertex, so this problem fits into the class of Locally checkable labeling (LCL) problems. However, the complexity of the $k$-level Hierarchical $2\frac{1}{2}$-Coloring problem is $\Theta(n^{1/k})$, for $k\in\mathbb{Z}^+$. The upper and lower bounds hold for both general graphs and trees, and for both randomized and deterministic algorithms. 2. Consider any LCL problem on bounded degree trees. We prove an automatic-speedup theorem that states that any randomized $n^{o(1)}$-time algorithm solving the LCL can be transformed into a deterministic $O(\log n)$-time algorithm. Together with a previous result, this establishes that on trees, there are no natural deterministic complexities in the ranges $\omega(\log^* n)$---$o(\log n)$ or $\omega(\log n)$---$n^{o(1)}$. 3. We expose a gap in the randomized time hierarchy on general graphs. Any randomized algorithm that solves an LCL problem in sublogarithmic time can be sped up to run in $O(T_{LLL})$ time, which is the complexity of the distributed Lovasz Local lemma problem, currently known to be $\Omega(\log\log n)$ and $O(\log n)$.
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an exponential separation between randomized and deterministic complexity in the Local Model
Foundations of Computer Science, 2016Co-Authors: Yijun Chang, Tsvi Kopelowitz, Seth PettieAbstract:Over the past 30 years numerous algorithms have been designed for symmetry breaking problems in the Local Model, such as maximal matching, MIS, vertex coloring, and edge coloring. For most problems the best randomized algorithm is at least exponentially faster than the best deterministic algorithm. We prove that these exponential gaps are necessary and establish numerous connections between the deterministic and randomized complexities in the Local Model. Each of our results has a very compelling take-away message: 1) Building on the recent randomized lower bounds of Brandt et al. [1], we prove that the randomized complexity of Δ-coloring a tree with maximum degree Δ is O(log Δ log n + log*n), for any Δ > = 55, whereas its deterministic complexity is Ω(log Δ n) for any Δ > = 3. This also establishes a large separation between the deterministic complexity of Δ-coloring and (Δ+1)-coloring trees. 2) We prove that any deterministic algorithm for a natural class of problems that runs in O(1) + o(log Δ n) rounds can be transformed to run in O(log*n - log*Δ + 1) rounds. If the transformed algorithm violates a lower bound (even allowing randomization), then one can conclude that the problem requires Ω(log Δ n) time deterministically. This gives an alternate proof that deterministically Δ-coloring a tree with small Δ takes Ω(log Δ n) rounds. 3) We prove that the randomized complexity of any natural problem on instances of size n is at least its deterministic complexity on instances of size √log n. This shows that a deterministic Ω(log Δ n) lower bound for any problem (Δ-coloring a tree, for example) implies a randomized Ω(log Δ log n) lower bound. It also illustrates that the graph shattering technique employed in recent randomized symmetry breaking algorithms is absolutely essential to the Local Model. For example, it is provably impossible to improve the 2O(√log log n) term in the complexities of the best MIS and (Δ+1)-coloring algorithms without also improving the 2O(√log n)-round Panconesi-Srinivasan algorithm.