arXiv subjects

Suat Gumussoy

Publications and source records attributed to Suat Gumussoy.

46 records · Page 3Linked to original sources

arXiv2020

Remarks on H-infinity Controller Design for SISO Plants with Time Delays

The skew Toeplitz approach is one of the well developed methods to design H-infinity controllers for infinite dimensional systems. In order to be able to use this method the plant needs to be factorized in some special manner. This paper investigates the largest class of SISO time delay systems for which the special factorizations required by the skew Toeplitz approach can be done. Reliable implementation of the optimal controller is also discussed. It is shown that the finite impulse response (FIR) block structure appears in these controllers not only for plants with I/O delays, but also for general time-delay plants.

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arXiv2020

Control of Systems with Infinitely Many Unstable Modes and Strongly Stabilizing Controllers Achieving a Desired Sensitivity

In this paper we consider a class of linear time invariant systems with infinitely many unstable modes. By using the parameterization of all stabilizing controllers, we show that H-infinity controllers for such systems can be computed using the techniques developed earlier for infinite dimensional plants with finitely many unstable modes. We illustrate connections between the problem solved here and an indirect method for strongly stabilizing H-infinity controller design for systems with time delays.

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arXiv2020

Controller Tuning for Active Queue Management Using a Parameter Space Method

In recent years, different mathematical models have been proposed for widely used internet control mechanisms. Simple low order controllers (such as PID, and Smith predictor based linear controllers that are easy to implement) are desired for network traffic management. In order to design such simple controllers for Active Queue Management (AQM), delay based linear models have been considered. In this paper we discuss tuning of the PID controllers by using a parameter space method, which computes stability regions of a class of quasi-polynomials in terms of free controller parameters.

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arXiv2019

Analytic Solution of a Delay Differential Equation Arising in Cost Functionals for Systems with Distributed Delays

The solvability of a delay differential equation arising in the construction of quadratic cost functionals, i.e. Lyapunov functionals, for a linear time-delay system with a constant and a distributed delay is investigated. We present a delay-free auxiliary ordinary differential equation system with algebraically coupled split-boundary conditions, that characterizes the solutions of the delay differential equation and is used for solution synthesis. A spectral property of the time-delay system yields a necessary and sufficient condition for existence and uniqueness of solutions to the auxiliary system, equivalently the delay differential equation. The result is a tractable analytic solution framework to the delay differential equation.

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arXiv2019

Power and Thermal Analysis of Commercial Mobile Platforms: Experiments and Case Studies

State-of-the-art mobile processors can deliver fast response time and high throughput to maximize the user experience. However, high performance comes at the expense of larger power density, which leads to higher skin temperatures. Since this can degrade the user experience, there is a strong need for power consumption and thermal analysis in mobile processors. In this paper, we first perform experiments on the Nexus 6P phone to study the power, performance and thermal behavior of modern smartphones. Using the insight from these experiments, we propose a control algorithm that throttles select applications without affecting other apps. We demonstrate our governor on the Exynos 5422 processor employed in the Odroid-XU3 board.

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arXiv2018

Power-Temperature Stability and Safety Analysis for Multiprocessor Systems

Modern multiprocessor system-on-chips (SoCs) integrate multiple heterogeneous cores to achieve high energy efficiency. The power consumption of each core contributes to an increase in the temperature across the chip floorplan. In turn, higher temperature increases the leakage power exponentially, and leads to a positive feedback with nonlinear dynamics. This paper presents a power-temperature stability and safety analysis technique for multiprocessor systems. This analysis reveals the conditions under which the power-temperature trajectory converges to a stable fixed point. We also present a simple formula to compute the stable fixed point and maximum thermally-safe power consumption at runtime. Hardware measurements on a state-of-the-art mobile processor show that our analytical formulation can predict the stable fixed point with an average error of 2.6%. Hence, our approach can be used at runtime to ensure thermally safe operation and guard against thermal threats.

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arXiv2018

Comments on: "Lyapunov matrices for a class of time delay systems" by V. L. Kharitonov

We prove that an auxiliary two-point boundary value problem presented in V. L. Kharitonov, Lyapunov matrices for a class of time delay systems, Systems & Control Letters 55 (2006) 610-617 has linearly dependent boundary conditions, and consequently a unique solution does not exist. Therefore, the two-point boundary value problem presented therein fails to be a basis for constructing Lyapunov matrices for the class of time delay systems investigated.

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arXiv2011

Combining Convex-Concave Decompositions and Linearization Approaches for solving BMIs, with application to Static Output Feedback

A novel optimization method is proposed to minimize a convex function subject to bilinear matrix inequality (BMI) constraints. The key idea is to decompose the bilinear mapping as a difference between two positive semidefinite convex mappings. At each iteration of the algorithm the concave part is linearized, leading to a convex subproblem.Applications to various output feedback controller synthesis problems are presented. In these applications the subproblem in each iteration step can be turned into a convex optimization problem with linear matrix inequality (LMI) constraints. The performance of the algorithm has been benchmarked on the data from COMPleib library.

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arXiv2010

H2 for HIFOO

HIFOO is a public-domain Matlab package initially designed for Hinfinity fixed-order controller synthesis, using nonsmooth nonconvex optimization techniques. It was later on extended to multi-objective synthesis, including strong and simultaneous stabilization under Hinfinity constraints. In this paper we describe a further extension of HIFOO to H2 performance criteria, making it possible to address mixed H2/Hinfinity synthesis. We give implementation details and report our extensive benchmark results.

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arXiv2009

Multiobjective Robust Control with HIFOO 2.0

Multiobjective control design is known to be a difficult problem both in theory and practice. Our approach is to search for locally optimal solutions of a nonsmooth optimization problem that is built to incorporate minimization objectives and constraints for multiple plants. We report on the success of this approach using our public-domain Matlab toolbox HIFOO 2.0, comparing our results with benchmarks in the literature.

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