Engineering Commons^™

Properties And Determination Of Optimal Decentralized Feedback Structure, Kangsong Han

Theses

In this thesis, the decentralized feedback structure for large scale, linear time invariant systems is studied. The internal differences and the relationship between decentralized feedback structure and centralized feedback structure are discussed. The conventional diagonal feedback structure. corresponding to the classical single loop design strategy, is first analyzed. This is followed by an arbitrary decentralized information flow constraint which is dependent upon the actual plant characteristics. Although signal flow graphs have limited use in describing decentralized control systems. the concept of a control cycle unit based on signal flow is introduced as a supplementary tool to characterize some fixed modes …

Reduction Of Acoustic Feedback Oscillations By Use Of Spectrum Shifting, Youssef Abdelilah

Theses

The problem of whistling noise or self-oscillation in public address systems operating in closed halls or rooms can be very disturbing to the listeners. This noise is sustained when the positive acoustic feedback, of the public address-room system, meets the oscillation criteria. This feedback system results from the acoustic sound signal reflected off the room walls and any other obstacles in the room, originating from the public address speakers and then re-entering the microphone.

When all of the audio signal components entering the public address system are shifted by a frequency increment Δf of 6 Hz, an increase of 5 …