Artificial Whiskers: Structural Characterization and Implications for Adaptive Robots

Whisking is an active exploratory process during which rodents sweep their macro vibrissae (whiskers) across surfaces to detect prominent environmental features (object location, surface textures, friction, and shapes). The resulting sensory stimulation is typically rich in both spatial and temporal structure, and is used to guide a host of adaptive behaviors. This article explores whisker systems as a sensory modality in rodents and robots with respect to their potential for adaptive behavior. To further our understanding of the role played by the morphology (shape and material properties) of whiskers, we present and discuss the results of simulations of conical and cylindrical whiskers. Our results show that for a given mass a conical whisker is (a) stiffer, (b) more selective for particular modes of vibration, and (c) more robust against fractures. We also describe the design and implementation of a bio-inspired active sensing system built with whiskers from real rats glued to capacitor microphones. Each whisker is capable of detecting very weak mechanical forces applied to its tip. Different resonance frequencies are induced in the whisker according to the object the whisker touches or is touched by. Our experimental results show that the interval of elicited frequencies ranges from approximately 230Hz to 3kHz. We suggest that this range of frequencies is particularly useful for discriminating textures with different spatial frequencies and other environmental features.