Browsing by Subject "Closed loop systems"
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Item Open Access Adaptive human pilot model for uncertain systems(IEEE, 2019-06) Tohidi, Shahab; Yıldız, YıldırayInspired by humans' ability to adapt to changing environments, this paper proposes an adaptive human model that mimics the crossover model despite input bandwidth deviations and plant uncertainties. The proposed human pilot model structure is based on the model reference adaptive control, and the adaptive laws are obtained using the Lyapunov-Krasovskii stability criteria applied to the overall closed loop system including the human pilot and the plant. The proposed model can be employed for human-in-the-Ioop stability and performance analyses with different controllers and plant types. A numerical example is used to demonstrate the effectiveness of the presented method.Item Open Access Numerical computation of H∞ optimal controllers for time delay systems using YALTA(Elsevier B.V., 2016) Yeğin, M. O.; Özbay, HitayNumerical computation of H∞ controllers for time delay systems has been a challenge since 1980s. Even though significant techniques are developed to obtain direct optimal controllers, application of these methods may require manual computation depending on the plant. In this paper, an alternative computational technique is proposed for direct optimal controllers originally obtained by Toker and Özbay (1995). The new controller expression contains finite dimensional transfer functions and an infinite dimensional term, which is stable. Thus it is suitable for finite dimensional approximations and practical non-fragile implementations. In this method, in order to eliminate manual computation of the plant factorization for neutral and retarded delay systems YALTA (a tool developed at INRIA) is used. The new controller computation is implemented in Matlab, and it is illustrated on an example. © 2016Item Open Access Observer based friction cancellation in mechanical systems(IEEE, 2014-10) Odabaş, Caner; Morgül, ÖmerAn adaptive nonlinear observer based friction compensation for a special time delayed system is presented in this paper. Considering existing delay, an available Coulomb observer is modified and closed loop system is formed by using a Smith predictor based controller as if the process is delay free. Implemented hierarchical feedback system structure provides two-degree of freedom and controls both velocity and position separately. For this purpose, controller parametrization method is used to extend Smith predictor structure to the position control loop for different types of inputs and disturbance attenuation. Simulation results demonstrate that without requiring much information about friction force, the method can significantly improve the performance of a control system in which it is applied. © 2014 Institute of Control, Robotics and Systems (ICROS).Item Open Access On stabilizing with PID controllers(IEEE, 2007-06) Saadaoui, K.; Özgüler, A. BülentIn this paper we give an algorithm that determines the set of all stabilizing proportional-integral-derivative (PID) controllers that places the poles of the closed loop system in a desired stability region S. The algorithm is applicable to linear, time invariant, single-input single-output plants. The solution is based on a generalization of the Hermite-Biehler theorem applicable to polynomials with complex coefficients and the the application of a stabilizing gain algorithm to three auxiliary plants. ©2007 IEEE.Item Open Access Stability analysis of human–adaptive controller interactions(American Institute of Aeronautics and Astronautics (AIAA), 2017) Yücelen, T.; Yıldız, Yıldıray; Sipahi, R.; Yousefi, Ehsan; Nguyen, N.In this paper, stability of human in the loop model reference adaptive control architectures is analyzed. For a general class of linear human models with time-delay, a fundamental stability limit of these architectures is established, which depends on the parameters of this human model as well as the reference model parameters of the adaptive controller. It is shown that when the given set of human model and reference model parameters satisfy this stability limit, the closed-loop system trajectories are guaranteed to be stable. © 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.