Bioinspired active whisker sensor for geometry detection of high aspect ratio microholes with simultaneous actuation and sensing capability

Abstract

This paper presents a whisker transducer (WT)—inspired by a rat’s vibrissal tactile location perception—that can be used to detect the geometry of high aspect ratio microholes. The WT acts as both the actuator that generates whisking movement and the sensor that detects the mechanical impedance at its tip. This unique, simultaneous actuation-and-sensing capability is achieved through a 2 × 2 transduction matrix model that characterizes both the forward actuation and backward sensing functions of the transducer. The WT imitates a rat’s vibrissal location perception when driven by a special signal with a low-frequency component and a high-frequency component. The low-frequency component plays the role of the ‘whisking signal,’ encoding the whisker position over time, and the high-frequency component plays the role of the ‘touch signal,’ encoding the onset time of mechanical contact. The combination of these two signals allows the WT to detect the location of an object. The proposed transducer and location detection algorithm are validated using a miniature prototype fabricated through micro-EDM process. The achieved geometry measurement capability is of high linearity (R2 > 0.99) and low measurement uncertainty (200 nm). Its potential application in detecting the taper of high aspect ratio microholes is also demonstrated.