Some distributed optimization applications require privacy, meaning that the values of certain parameters local to a node should not be revealed to other nodes in the network during the joint optimization process. A s...
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Some distributed optimization applications require privacy, meaning that the values of certain parameters local to a node should not be revealed to other nodes in the network during the joint optimization process. A special case is the problem of private distributed averaging, in which a network of nodes computes the global average of individual node reference values in a distributed manner while preserving the privacy of each reference. We present simple iterative methods that guarantee accuracy (i.e., the exact asymptotic computation of the global average) and privacy (i.e., no node can estimate another node's reference value). To achieve this, we require that the digraph modeling the communication between nodes satisfy certain topological conditions. Our method is hot-pluggable (meaning no reinitialization of the averaging process is required when the network changes or a node enters or leaves, when there is a communication or computation fault, or when a node's reference value changes);it does not require an initial scrambling phase;it does not inject noise or other masking signals into the distributed computation;it does not require random switching of edge weights;and it does not rely on homomorphic encryption.
The regulators based on PI control law continue to be the key elements in many of the industrial systems for their control. Likewise, the wind power generation systems (WPGSs) also make extensive use of PI regulators ...
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The regulators based on PI control law continue to be the key elements in many of the industrial systems for their control. Likewise, the wind power generation systems (WPGSs) also make extensive use of PI regulators in their control schemes. The enhanced performance of these WPGS depends on proper selection of the PI regulator parameters. This paper deals with the control of a grid-tied permanent magnet synchronous generator (PMSG)-based WPGS wherein, a new attempt has been depicted to apply the most optimum design of the involved PI regulator parameters for the proposed WPGS based on standard performance indices making use of four popular optimization algorithms namely genetic algorithm (GA), cultural algorithm (CA), particle swarm optimization (PSO) and artificial bee colony (ABC). An informative discussion has also been presented which would be useful for practicing engineers/researchers to select flexibly and reasonably the PI regulators parameters meant for the control of the proposed WPGS. A detailed simulation model developed in MATLAB/Simulink has been used to analyze the performance of the proposed PMSG-based WPGS employed with the most optimum values of PI regulator parameters. The performances of WPGS have been compared while the most optimum PI regulator parameters have been included in the control system, and also when incorporating the PI regulator parameters in WPGS control designed via classical D-partition technique. The results obtained under gradually changing wind speed profile show the improvement in the performance of WPGS in terms of peak overshoot, time response and waveform oscillations. The experimental validation of the control performances have been carried out by way of real-time hardware-in-the-loop (HIL) testing making use of Typhoon HIL402 emulator and TMS320F28335 digital signal controller. The obtained real time HIL results are in close agreement to the results obtained in simulations using MATLAB/Simulink. A deviation of less than
The research work presented here tackles the problem of finding the optimum value for hyper-parameters, such as number of layers and number of neurons per layer, for a fully-connected Artificial Neural Network (ANN), ...
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The research work presented here tackles the problem of finding the optimum value for hyper-parameters, such as number of layers and number of neurons per layer, for a fully-connected Artificial Neural Network (ANN), particularly in regression problems. A proposed optimization strategy is tested on different datasets related to diverse industrial applications: (1) prediction of the performance of exploration algorithms for mobile robots, (2) prediction of the compressive strength of concrete, (3) prediction of energy output from a power plant;and (4) prediction of wine quality. Different evaluation metrics, such as Pearson correlation coefficient (R), Square Correlation Coefficient (R-2), Absolute Relative Error ( RAE), Root Mean Square Error (RMSE), and Mean Absolute Error (MAE), are used to determine the best performing prediction model when the hyper-parameter optimization algorithms are used. That result is compared to the performance of the best model previously reported in the literature on the same dataset in order to determine the gains achieved by using the hyper-parameter optimization strategy under test.
In this letter, we review an existing distributed least-squares solver and share some new insights on it. Then, by the observation that an estimation of a constant vector under output noise can be translated into find...
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In this letter, we review an existing distributed least-squares solver and share some new insights on it. Then, by the observation that an estimation of a constant vector under output noise can be translated into finding the least-squares solution, we present an algorithm for distributed estimation of the state of linear time-invariant systems under measurement noise. The proposed algorithm consists of a network of local observers, where each of them utilizes local measurements and information transmitted from the neighbors. It is proven that even under non-vanishing and time-varying measurement noise, we could obtain an almost best possible estimate with arbitrary precision. Some discussions regarding the plug-and-play operation are also given.
Purpose This paper aims to present a new model for solving the integrated production planning and scheduling. Usually, the two decision levels are treated sequentially because of their complexity. Scheduling depends o...
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Purpose This paper aims to present a new model for solving the integrated production planning and scheduling. Usually, the two decision levels are treated sequentially because of their complexity. Scheduling depends on the lot sizes calculated at the tactical level and ignoring scheduling constraints generates unrealistic and inconsistent decisions. Therefore, integrating more detail scheduling constraint in production planning is important for managing efficiently operations. Therefore, an integrated model was developed, and two evolutionary optimization approaches were suggested for solving it, namely, genetic algorithm (GA) and the hybridization of simulated annealing (SA) with GA HSAGA. The proposed algorithms have some parameters that must be adjusted using Taguchi method. Therefore, to evaluate the proposed algorithm, the authors compared the results given by GA and the hybridization. The SA-based local search is embedded into a GA search mechanism to move the GA away from being closed within local optima. The analysis shows that the combination of simulated annealing with GA gives better solutions and minimizes the total production costs. Design/methodology/approach The paper opted for an approached resolution method particularly GA and simulated annealing. The study represents a comparison between the results found using GA and the hybridization of simulated annealing and GA. A total of 45 instances were studied to evaluate job-shop problems of different sizes. Findings The results illustrate that for 36 instances of 45, the hybridization of simulated annealing and GA HSAGA has provided best production costs. The efficiency demonstrated by HSAGA approach is related to the combination between the exploration ability of GA and the capacity to escape local optimum of simulated annealing. Originality/value This study provides a new resolution approach to the integration of planning and scheduling while considering a new operational constrain. The model suggested
In this letter we propose a method to exactly certify the complexity of an active-set method which is based on reformulating strictly convex quadratic programs to nonnegative least-squares problems. The exact complexi...
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In this letter we propose a method to exactly certify the complexity of an active-set method which is based on reformulating strictly convex quadratic programs to nonnegative least-squares problems. The exact complexity of the method is determined by proving the correspondence between the method and a standard primal active-set method for quadratic programming applied to the dual of the quadratic program to be solved. Once this correspondence has been established, a complexity certification method which has already been established for the primal active-set method is used to also certify the complexity of the nonnegative least-squares method. The usefulness of the proposed method is illustrated on a multi-parametric quadratic program originating from model predictive control of an inverted pendulum.
Local optimization of adsorption systems inherently involves different scales: within the substrate, within the molecule, and between the molecule and the substrate. In this work, we show how the explicit modeling of ...
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Local optimization of adsorption systems inherently involves different scales: within the substrate, within the molecule, and between the molecule and the substrate. In this work, we show how the explicit modeling of different characteristics of the bonds in these systems improves the performance of machine learning methods for optimization. We introduce an anisotropic kernel in the Gaussian process regression framework that guides the search for the local minimum, and we show its overall good performance across different types of atomic systems. The method shows a speed-up of up to a factor of two compared with the fastest standard optimization methods on adsorption systems. Additionally, we show that a limited memory approach is not only beneficial in terms of overall computational resources but can also result in a further reduction of energy and force calculations.
This letter revisits the problem of synthesizing the optimal control laws for linear systems with a quadratic cost. Traditionally, these laws are computed using the Hamilton-Jacobi-Bellman method, where the solution t...
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This letter revisits the problem of synthesizing the optimal control laws for linear systems with a quadratic cost. Traditionally, these laws are computed using the Hamilton-Jacobi-Bellman method, where the solution to the original problem is obtained by solving the Riccati equation, which hinges upon a priori information of the optimal cost function. Within the general Krotov global optimal control framework, though being less explored in the literature, that information is no longer needed. However, utilizing this framework, the original optimization problem is translated into a non-convex problem, which is solved by using iterative methods. In this letter, we propose a new method to compute a direct (non-iterative) solution by transforming the resulting non-convex optimization problem into a convex problem. It turns out that the proposed method naturally leads to the Riccati inequality as the crucial intermediate step, of which the origin was not well understood, although it serves as a strong backbone to address linear quadratic problems and other significant linear system theoretic results. Numerical results and future directions, particularly for solving the optimal control problem for bilinear systems, are also provided to demonstrate the usability of the proposed method.
Although adaptive optimization algorithms have been successful in many applications, there are still some mysteries in terms of convergence analysis that have not been unraveled. This paper provides a novel non-convex...
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The Generalized Moving Peaks Benchmark (GMPB) [1] is a tool for generating continuous dynamic optimization problem instances with controllable dynamic and morphological characteristics. GMPB has been used in recent Co...
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