The Experts below are selected from a list of 110565 Experts worldwide ranked by ideXlab platform
Miroslav Fikar - One of the best experts on this subject based on the ideXlab platform.
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Complexity Reduction of explicit model predictive control via separation
Automatica, 2013Co-Authors: Michal Kvasnica, Juraj Hledik, Ivana Rauova, Miroslav FikarAbstract:The problem of reducing Complexity of explicit MPC feedback laws for linear systems is considered. We propose to simplify controllers defined by continuous Piecewise Affine (PWA) functions by employing separating functions. If a state resides in a region where the optimal control action attains a saturated value, the optimal control move is determined from the sign of the separator. Thus, instead of storing all regions, only the unconstrained regions and the separator are needed. We propose several approaches to construct separators with different efficacy and properties.
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clipping based Complexity Reduction in explicit mpc
IEEE Transactions on Automatic Control, 2012Co-Authors: Michal Kvasnica, Miroslav FikarAbstract:The idea of explicit model predictive control (MPC) is to characterize optimal control inputs as an explicit piecewise affine (PWA) function of the initial conditions. The function, however, is often too complex and either requires too much processing power to evaluate on-line, or consumes a prohibitive amount of memory. The paper focuses on the memory issue and proposes a novel method of replacing a generic continuous PWA function by a different function of significantly lower Complexity in such a way that the simple function guarantees the same properties as the original. The idea is based on eliminating regions of the PWA function over which the function attains a saturated value. An extensive case study is presented which confirms that a significant Reduction of Complexity is achieved in general.
Manfred Morari - One of the best experts on this subject based on the ideXlab platform.
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optimal Complexity Reduction of polyhedral piecewise affine systems
Automatica, 2008Co-Authors: Tobias Geyer, Fabio Danilo Torrisi, Manfred MorariAbstract:This paper focuses on the NP-hard problem of reducing the Complexity of piecewise polyhedral systems (e.g. polyhedral piecewise affine (PWA) systems). The results are fourfold. Firstly, the paper presents two computationally attractive algorithms for optimal Complexity Reduction that, under the assumption that the system is defined over the cells of a hyperplane arrangement, derive an equivalent polyhedral piecewise system that is minimal in the number of polyhedra. The algorithms are based on the cells and the markings of the hyperplane arrangement. In particular, the first algorithm yields a set of disjoint (non overlapping) merged polyhedra by executing a branch and bound search on the markings of the cells. The second approach leads to non-disjoint (overlapping) polyhedra by formulating and solving an equivalent (and well-studied) logic minimization problem. Secondly, the results are extended to systems defined on general polyhedral partitions (and not on cells of hyperplane arrangements). Thirdly, the paper proposes a technique to further reduce the Complexity of piecewise polyhedral systems if the introduction of an adjustable degree of error is acceptable. Fourthly, the paper shows that based on the notion of the hyperplane arrangement PWA state feedback control laws can be implemented efficiently. Three examples, including a challenging industrial problem, illustrate the algorithms and show their computational effectiveness in reducing the Complexity by up to one order of magnitude.
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controller Complexity Reduction for piecewise affine systems through safe region elimination
Conference on Decision and Control, 2007Co-Authors: Frank J Christophersen, Melanie N Zeilinger, Colin N Jones, Manfred MorariAbstract:We consider the class of piecewise affine optimal state feedback control laws applied to discrete-time piecewise affine systems, motivated by recent work on the computation of closed-form MPC controllers. The storage demand and Complexity of these optimal closed-form solutions limit their applicability in most real-life situations. In this paper we present a novel algorithm to a posteriori reduce the storage demand and Complexity of the closed-form controller without losing closed-loop stability or all time feasibility while guaranteeing a bounded performance decay compared to the optimal solution. The algorithm combines simple polyhedral manipulations with (multi-parametric) linear programming and the effectiveness of the algorithm is demonstrated on a large numerical example.
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Complexity Reduction of receding horizon control
Conference on Decision and Control, 2003Co-Authors: P Grieder, Manfred MorariAbstract:The off-line solution of constrained optimal control problems has garnered much attention because implementation can be realized with a simple look-up table. In this paper, a detailed Complexity analysis of algorithms used to compute the explicit optimal control solution is given. Based on this analysis, two novel algorithms to compute controllers of significantly lower Complexity are presented. Stability and feasibility of the closed-loop system are guaranteed by both algorithms. Extensive simulation results suggest that, on average, the controller Complexity can be reduced by orders of magnitude at the cost of a performance decrease below 0.5%.
Michal Kvasnica - One of the best experts on this subject based on the ideXlab platform.
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Complexity Reduction of explicit model predictive control via separation
Automatica, 2013Co-Authors: Michal Kvasnica, Juraj Hledik, Ivana Rauova, Miroslav FikarAbstract:The problem of reducing Complexity of explicit MPC feedback laws for linear systems is considered. We propose to simplify controllers defined by continuous Piecewise Affine (PWA) functions by employing separating functions. If a state resides in a region where the optimal control action attains a saturated value, the optimal control move is determined from the sign of the separator. Thus, instead of storing all regions, only the unconstrained regions and the separator are needed. We propose several approaches to construct separators with different efficacy and properties.
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clipping based Complexity Reduction in explicit mpc
IEEE Transactions on Automatic Control, 2012Co-Authors: Michal Kvasnica, Miroslav FikarAbstract:The idea of explicit model predictive control (MPC) is to characterize optimal control inputs as an explicit piecewise affine (PWA) function of the initial conditions. The function, however, is often too complex and either requires too much processing power to evaluate on-line, or consumes a prohibitive amount of memory. The paper focuses on the memory issue and proposes a novel method of replacing a generic continuous PWA function by a different function of significantly lower Complexity in such a way that the simple function guarantees the same properties as the original. The idea is based on eliminating regions of the PWA function over which the function attains a saturated value. An extensive case study is presented which confirms that a significant Reduction of Complexity is achieved in general.
Luciano Agostini - One of the best experts on this subject based on the ideXlab platform.
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solutions for dmm 1 Complexity Reduction in 3d hevc based on gradient calculation
Latin American Symposium on Circuits and Systems, 2016Co-Authors: Mario Saldanha, Bruno Zatt, Marcelo Porto, Luciano Agostini, Gustavo SanchezAbstract:This paper proposes a space exploration over gradient-based algorithms to obtain time savings when applying Depth Modeling Mode (DMM) 1 on 3D High Efficiency Video Coding (3D-HEVC) depth maps coding. Four filtering algorithms exploring depth maps characteristics by applying a gradient filter in the depth block borders were evaluated. These filters are applied to detect the best positions to evaluate DMM-1 algorithm, without the use of a semi-brute force approach. Experimental analysis demonstrates that the proposed solutions are capable to achieve time saving results ranging from 4.9% to 8.2%, with a drawback ranging from 0.33% to 1.47% in terms of BD-Rate increase.
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a Complexity Reduction algorithm for depth maps intra prediction on the 3d hevc
Visual Communications and Image Processing, 2014Co-Authors: Gustavo Sanchez, Mario Saldanha, Gabriel Balota, Bruno Zatt, Marcelo Porto, Luciano AgostiniAbstract:This paper proposes a Complexity Reduction algorithm for the depth maps intra prediction of the emerging 3D High Efficiency Video Coding standard (3D-HEVC). The 3D-HEVC introduces a new set of specific tools for the depth map coding that includes four Depth Modeling Modes (DMM) and these new features have inserted extra effort on the intra prediction. This extra effort is undesired and contributes to increasing the power consumption, which is a huge problem especially for embedded-systems. For this reason, this paper proposes a Complexity Reduction algorithm for the DMM 1, called Gradient-Based Mode One Filter (GMOF). This algorithm applies a filter to the borders of the encoded block and determines the best positions to evaluate the DMM 1, reducing the computational effort of DMM 1 process. Experimental analysis showed that GMOF is capable to achieve, in average, a Complexity Reduction of 9.8% on depth maps prediction, when evaluating under Common Test Conditions (CTC), with minor impacts on the quality of the synthesized views.
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Complexity Reduction for 3d hevc depth maps intra frame prediction using simplified edge detector algorithm
International Conference on Image Processing, 2014Co-Authors: Gustavo Sanchez, Mario Saldanha, Gabriel Balota, Bruno Zatt, Marcelo Porto, Luciano AgostiniAbstract:This paper presents a new mode decision for the depth maps intra-frame prediction in 3D-HEVC. The proposed technique decides if the traditional High Efficiency Video Coding-based (HEVC) intra-frame prediction should be performed or skipped. This technique is inspired by the fact that traditional intra-frame prediction may generate artifacts in the synthesized views when an edge is encoded. The Simplified Edge Detector (SED) algorithm has been proposed to classify if a block contains an edge or a nearly constant region demanding a minimum processing overhead. Through software evaluations, SED algorithm was capable to obtain an average Complexity Reduction of 23.8% for depth maps coding with no quality losses.
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hevc fractional motion estimation Complexity Reduction for real time applications
Latin American Symposium on Circuits and Systems, 2014Co-Authors: Henrique Maich, Bruno Zatt, Luciano Agostini, Vladimir Afonso, Marcelo PortoAbstract:This paper presents a compression analysis about the High Efficiency Video Coding (HEVC) standard targeting a computational effort Reduction at the scope of the motion estimation (ME). Restricting the Prediction Units (PUs) — among a total of 24 sizes — to the 4 square-shaped sizes in the HEVC interframes prediction, it is possible to reduce in 74% the number of operations at the cost of 4% increase in the bit-rate, considering the Y-BD-Rate metric. Based on this evaluation, a simple hardware architecture is proposed to implement the Sum of Absolute Differences (SAD) used in the Fractional Motion Estimation (FME). The proposed architecture is able to calculate SAD with a rate of 30 Full HD (1920×1080) frames per second, requiring a frequency of 1.17GHz. It represents a 63% frequency Reduction compared to a scenario where all 24 PU sizes are evaluated.
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coding tree depth estimation for Complexity Reduction of hevc
Data Compression Conference, 2013Co-Authors: Guilherme Correa, Luciano Agostini, Pedro Assuncao, Luis A Da Silva CruzAbstract:The emerging HEVC standard introduces a number of tools which increase compression efficiency in comparison to its predecessors at the cost of greater computational Complexity. This paper proposes a Complexity control method for HEVC encoders based on dynamic adjustment of the newly proposed coding tree structures. The method improves a previous solution by adopting a strategy that takes into consideration both spatial and temporal correlation in order to decide the maximum coding tree depth allowed for each coding tree block. Complexity control capability is increased in comparison to a previous work, while compression losses are decreased by 70%. Experimental results show that the encoder computational Complexity can be downscaled to 60% with an average bit rate increase around 1.3% and a PSNR decrease under 0.07 dB.
Xin Deng - One of the best experts on this subject based on the ideXlab platform.
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a deep convolutional neural network approach for Complexity Reduction on intra mode hevc
International Conference on Multimedia and Expo, 2017Co-Authors: Xin DengAbstract:The High Efficiency Video Coding (HEVC) standard significantly saves coding bit-rate over the proceeding H.264 standard, but at the expense of extremely high encoding Complexity. In fact, the coding tree unit (CTU) partition consumes a large proportion of HEVC encoding Complexity, due to the brute-force search for rate-distortion optimization (RDO). Therefore, we propose in this paper a Complexity Reduction approach for intra-mode HEVC, which learns a deep convolutional neural network (CNN) model to predict CTU partition instead of RDO. Firstly, we establish a large-scale database with diversiform patterns of CTU partition. Secondly, we model the partition as a three-level classification problem. Then, for solving the classification problem, we develop a deep CNN structure with various sizes of convolutional kernels and extensive trainable parameters, which can be learnt from the established database. Finally, experimental results show that our approach reduces intramode encoding time by 62.25% and 69.06% with negligible Bj⊘ntegaard delta bit-rate of 2.12% and 1.38%, over the test sequences and images respectively, superior to other state-of-the-art approaches.
