Recently, different approaches have been proposed for local active noise control of headrest systems. The purpose with such systems is to achieve silent zones around the ear positions without headsets. In particular, it is of interest to cancel low frequency sound. This is the case, for example, at a chair headrest for drivers of diesel locomotives. In this paper, a robust feedback approach is proposed. Low complexity models are used in a robust pole-placement design that allows shaping of different sensitivity functions. Three sensitivity functions are considered, resulting in robustness margins of the feedback loop, selective noise feedback and annihilation of the noise at the ear position. The controller is calculated from two coupled polynomial equations. A simple one-channel headrest system was built in order to investigate control design trade-offs and the use of the internal model principle for cancellation of sound at the ear position. The design resulted in two coupled polynomial equations, one for the stability problem and the other for the disturbance rejection problem, where in particular the ear position is considered. Simple models were estimated describing the electroacoustical paths. These were used for pole placement design resulting in a controller of low complexity. Real experiments verified the expected modelled characteristic behaviour of the active noise control system. To design for a zone of quiet at the ear position rather than at the physical microphone position appears to be crucial. When attenuating disturbances at the ear by 10 dB, the sound is actually increased by 5 dB at the microphone.
Low complexity robust control of a headrest system based on virtual microphones and the internal model principle
Einfache robuste Regelung eines kopfstützenbasierten Systems zur Lärmminderung mit virtuellen Mikrophonen nach dem 'Internal Model Prinzip'
2002
8 Seiten, 4 Bilder, 10 Quellen
Conference paper
English
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