Computer Engineering / Bilgisayar Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/10

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Author: search.filters.author.Ayav, TolgaSubject: search.filters.subject.Feedback control

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Now showing 1 - 5 of 5
  • Conference Object
    Neuro-Fuzzy Controller in Real-Time Feedback Schedulers
    (Izmir Institute of Technology, 2002) Ayav, Tolga; Yılmaz, Sinan
    Traditional scheduling algorithms worked on closed and highly predictable environments. However present day systems need to work in more open and unpredictable environments; such as mobile robots, on-line trading, e-commerce, multimedia that cannot be driven well with traditional open-loop algorithms. A new scheduling paradigm, feedback control scheduling, therefore has been presented recently to fulfil the requirements of such systems. This algorithm defines error terms for schedules, monitors the error, and continuously adjusts the schedule to maintain stable performance. When PID (Proportional-Integral-Derivative) controller is used to control the CPU utilization, one of the problems faced is that when utilization setpoint is closer to 100%, in severely overloaded conditions, systems can have a longer settling time than the analysis based on the linear model since utilization feedback saturates at 100%. To overcome this problem, a neuro-fuzzy controller is designed instead of PID. Simulations showed that settling time with the neuro-fuzzy controller is approximately four times shorter than the one with the PID controller.
  • Conference Object
    Stability Properties of Adaptive Real-Time Feedback Scheduling: a Statistical Approach
    (Nessuna, 2004) Ayav, Tolga; Ferrari-Trecate, Giancarlo; Yılmaz, Sinan
    This paper focuses on the statistical analysis of an adaptive real-time feedback scheduling technique based on imprecise computation. We consider two-version tasks made of a mandatory and an optional part to be scheduled according to a feedback control rate-monotonic algorithm. A Proportional-Integral-Derivative (PID) control action provides the feedback strategy for deciding about the execution or rejection of the optional sub-tasks. By modelling the task execution times as random variables, we compute the probability density of the CPU utilization and derive conditions on PID parameters guaranteeing the stability of the overall system around a desired level of CPU utilization. This allows us to highlight the tasks statistics and the scheduling parameters that affect critically stability. The analysis is developed by first exploiting a number of simplifying assumptions that are progressively removed. The main results are also demonstrated through monte-carlo simulations of the scheduling algorithm.
  • Conference Object
    Citation - WoS: 1
    Feedback Control Static Scheduling for Real-Time Distributed Embedded Systems
    (Institute of Electrical and Electronics Engineers Inc., 2005) Ayav, Tolga; Sorel, Yves
    This paper presents an implementation of feedback control strategy on distributed static scheduling. The static schedule is created taking into account the average execution times of the tasks. Feedback control algorithm handles the unestimated dynamic behaviors in the system and keeps the performance at a desired level. The approach of feedback control supporting static scheduling yields more flexible scheduling, low scheduling overhead and better resource utilization while preserving the realtime constraints.
  • Conference Object
    Citation - Scopus: 9
    Adaptive Rtp Rate Control Method
    (Institute of Electrical and Electronics Engineers Inc., 2011) Tos, Uras; Ayav, Tolga
    In this paper, we present an adaptive method for maximizing network bandwidth utilization for the real-time applications. RTP protocol is chosen as the transport protocol and the network utilization is provided by increasing and decreasing the transmission rate of the RTP traffic. Our method employs a PID controller that keeps the RTP packet loss fraction at a predefined reference point. Packet loss fraction parameter is gathered from the RTCP receiver reports and fed into the PID controller that controls the transmission rate of the RTP traffic. Simulations are performed to demonstrate the effectiveness of the method under a bottleneck network configuration with background UDP traffic competing against the RTP traffic for the available bandwidth.
  • Article
    Optimal Control for Real-Time Feedback Rate-Monotonic Schedulers
    (Springer Verlag, 2005) Ayav, Tolga; Ferrari-Trecate, Giancarlo
    This paper presents an optimal control scheme for a real-time feedback control rate-monotonic scheduling (FC-RMS) system. We consider two-version tasks composed of a mandatory and an optional part to be scheduled according to the FC-RMS. In FC-RMS, the controller provides a feedback strategy for deciding about the execution or rejection of the optional sub-tasks. By modeling the task execution times as random variables, we first find the statistical model of FC-RMS and then we design a pure optimal controller and an optimal controller with feedforward integral compensation. The comparison of these two schemes with common Proportional-Integral-Derivative (PID) controller highlights the benefit of the optimal scheme with integral compensation. The results are demonstrated through the real implementation of FC-RMS on RT-Linux.