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Effects of Neglecting Buffers in Feed-Forward Design for Web Servers

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Author

Summary, in English

This paper addresses a problem related to control of web servers. Due to implementation issues, relevant measurements are only taken over the a limit part of the server system, which leaves the controller unaware of what happens in buffers proceeding the actual web-server (for instance in the TCP/IP layers). We model this and reveals that the unmeasured buffering introduces an extra zero in the relationship between the process control-signal and output. Furthermore, it is shown that a measurement of a disturbance-input actually is state dependent. We also investigate how these new properties affects a traditional feed--forward design. The stability analysis suggests that under certain circumstances, the system becomes unstable due to the feedback mechanism introduced by the designed feed-forward. We verify the analysis by both simulations and experiments.

Publishing year

2009

Language

English

Document type

Conference paper

Topic

  • Control Engineering

Keywords

  • Feed-forward
  • queuing theory
  • modeling

Conference name

Fourth International Workshop on Feedback Control Implementation and Design in Computing Systems and Networks

Conference date

2009-04-16

Conference place

San Francisco, California, United States

Status

Published

Research group

  • LCCC