Browsing by Subject "Time delays"
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Item Open Access Air fuel ratio control using delay resistant closed loop reference model adaptive control(Hezarfen Havacılık ve Uzay Teknolojileri Enstitüsü, 2018) Yıldız, YıldırayThe focus of this paper is the air fuel ratio control of spark ignited engines. It is known that for an efficient removal of the pollutants from the exhaust gases, air fuel ratio has to be kept within a narrow band around the stoicometric ratio, which represents the condition where the air amount is perfectly matched with the fuel amount for a complete burn. The main challenges for this control problem are the inherent time delay of the system and uncertain dynamics. In this paper, employment of a high performance adaptive controller, which explicitly compensates for the delays without causing excessive oscillations, is proposed. The performance of this controller is demonstrated via simulation studies. To emphasize the importance of delay compensation, the controller is compared with the closed loop model reference adaptive controller, which do not have explicit delay compensation.Item Open Access Effect of time delays on the convergence speed of consensus dynamics(Bilkent University, 2020-01) Alhassan, Mohammed KamilWe discuss consensus problems under time delays. The presence of time delays results in an infinite-dimensional system rather than a system of ordinary differential equations. It has been shown that information transmission delays do not influence whether the system converges to a consensus value; however, further effects of delays are unknown. We show that time delays in most graphs decreases the convergence speed; while somewhat surprisingly, they can improve convergence in certain special graphs. We discuss the structure of graphs for which such improvement is possible.Item Open Access On the stabilization and stability robustness against small delays of some damped wave equations(IEEE, 1995) Morgül, O.In this note we consider a system which can be modeled by two different one-dimensional damped wave equations in a bounded domain, both parameterized by a nonnegative damping constant. We assume that the system is fixed at one end and is controlled by a boundary controller at the other end. We consider two problems, namely the stabilization and the stability robustness of the closed-loop system against arbitrary small time delays in the feedback loop. We propose a class of dynamic boundary controllers and show that these controllers solve the stabilization problem when the damping coefficient is nonnegative and stability robustness problem when the damping coefficient is strictly positive.Item Open Access Robust track following in Hard Disk Drives with time delays: An infinite dimensional approach(Elsevier, 2019-10) Yan, Y.; Özbay, Hitay; Lyuc, Z.Due to the existence of various sources of delays, the dynamical model of HDD (Hard Disk Drive) servo systems is actually infinite dimensional, although most of the existing algorithms simplified the model with Padé expansions or other finite dimensional approximations. In this paper, a robust loop shaping algorithm is developed for high accuracy track following of HDD servo systems with delays by using an H∞ synthesis approach for infinite dimensional systems. The H∞ controller is derived with a structure of an internal feedback loop including an FIR (Finite Impulse Response) filter and a first order IIR (Infinite Impulse Response) filter, which facilitates stable implementations. Digital implementation of the proposed control structure is further investigated by incorporating H∞ based sampled-data FIR filter design and approximation. Comparisons to other robust control methods are given, and the advantages of the proposed algorithm are demonstrated in terms of tracking TPI (Track-per-Inch) capability and transient responses using HDD factory measurement data.