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Mimicking the nonlinear compressive behavior of the mammalian cochlear amplifier that results in the compression of high-intensity sounds and amplification of faint stimuli can lead to transformative improvements in the dynamic range, sharpness of the response, and threshold of sound detection in cochlear implants to aid individuals with hearing loss. Furthermore, it can enhance the dynamic properties of sensors. This research on developing self-sensing artificial hair cells (AHCs) validates the phenomenological control algorithm established in Part I of the paper to achieve a cochlea-like response from the quadmorph AHCs. As the beam is excited, the voltage of the piezoelectric layers is measured and used to generate a control voltage. Consequently, the controller applies cubic damping to the AHC, while reducing linear damping near its first natural frequency to replicate the biological cochlea’s function. Experimental results validate the model built in Part I of the paper and the work is extended to implement a multi-channel AHC. The system works independent of external sensors and offers significant advantages over previous generations of AHCs such as the ability to embed AHCs in a limited space and to combine several AHCs in an array without the need for external feedback measurement devices.

 

Steady-state traveling waves in structures have been previously investigated for a variety of purposes including propulsion of objects and agitation of a surrounding medium. In the field of additive manufacturing, powder bed fusion (PBF) is a commonly used process that uses heat to fuse regions of metallic or polymer powders within a loose bed. PBF processes require post-process removal of loose powder, which can be difficult when blind holes or complex internal geometry are present in the fabricated part. Here, a preliminary investigation of a simple part is conducted examining the use of traveling waves for post-process de-powdering of additively manufactured specimens. The generation of steady-state traveling waves in a structure is accomplished through excitation at a frequency between two adjacent resonant frequencies of the structure, resulting in two-mode excitation. This excitation can be generated by bonded piezoceramic elements actuated by a sinusoidal voltage signal. The response of the structure is affected by the parameters of the excitation, such as the particular frequency of the voltage signal, the placement of the piezoceramic actuators, and the phase difference in the signals applied to different actuators. Careful selection of these parameters allows adjustment of the quality, wavelength, and wave speed of the resulting traveling waves. In this work, open-top rectangular box specimens composed of sintered nylon powder and coated with fine sand are used to represent freshly fabricated parts yet-to-be cleaned of un-sintered powder. Steady-state traveling waves are excited in the specimens while variations in the frequency content and phase differences between actuation points of the excitation are used to affect the characteristics of the dynamic response. The effectiveness of several response types for the purpose of moving un-sintered nylon powder within the specimens is investigated.