Feedback control in engineering structures and in the inner ear

Elliott, Stephen J. (2005) Feedback control in engineering structures and in the inner ear. In Proceedings of Forum Acusticum 2005, Budapest. European Acoustics Association. 45 pp .

Abstract

The vibration of many engineering structures can be actively controlled using multiple local feedback loops. Careful choice of the actuator and sensor type, and of their relative positioning, can ensure that the system is robustly stable, and that its performance approaches that of a fully coupled feedback control system. The advantage of such a local strategy is that it reduces complexity, it can be implemented using multiple identical modules, and that its overall stability is insensitive to individual loop failures. Examples will be presented of the application of this approach to active vibration isolation and the active vibroacoustic control of panels. The active hearing process in the cochlea is also thought to consist of multiple local control loops, distributed along the basilar membrane. In this case, however, the feedback loops act to enhance the vibration rather than attenuate it. Their action is also very nonlinear, providing maximum enhancement at low sound levels. The analysis of these multiple, coupled, nonlinear feedback loops is challenging, but may provide insight into a number of aspects of hearing, particularly otoacoustic emissions.

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