ARTIFICIAL COCHLEAR HAIR CELLS USING ACTIVE PIEZOELECTRIC MATERIALS
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The inner hair cells (IHCs) and outer hair cells (OHCs) in the cochlea are vital components in the process of hearing. The IHCs are responsible for converting sound-induced vibration into electrical signals. The OHCs produce forces that amplify these vibrations and therefore enhance the electrical signals produced by the IHCs. The resulting cochlear amplifier produces a nonlinear amplification which gives the ear its ability to detect sound pressure levels ranging from 20 Pa to 20 Pa (0 to 120 dB).This paper presents the modeling and testing of an artificial hair cell (AHC) piezoelectric sensor inspired by the hair cells found in the mammalian ear. The sensor is a bimorph cantilever beam consisting of a sensing piezoceramic element and an actuating piezoceramic element bonded to a brass substrate. The sensing element is used to detect the mechanical motion of the beam. Output feedback control can be used to send a voltage signal to the actuating element and alter the frequency response of the beam. A control law, which modifies the linear damping term of the first mode and introduces cubic damping, is used to create a closed-loop system perched at a Hopf bifurcation. The result is a system that produces a nonlinear amplification of the beams mechanical response in a manner which mimics the nonlinear behavior of the mammalian cochlea. This active sensor is studied under base acceleration and the initial test results are compared to a finite element model. Simulations of the closed-loop system are examined for the system with a single mode and for the system with multiple modes.
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Volume 2: Mechanics and Behavior of Active Materials; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting
