Keeping It Simple: Bio-Inspired Threshold-Based Strain Sensing for Micro-Aerial Vehicles

Moths use hundreds of strain sensors (campaniform sensilla) on each wing to quickly respond to perturbations that may otherwise destabilize the moth during flight. A similar sensing approach could help stabilize micro-aerial vehicles (MAVs), but large sensor arrays are challenging due to the wiring and large latency that exists when capturing data from many traditional strain sensors. This work introduces a simplified bio-inspired strain sensor; the sensor interface and kinematics were inspired by campaniform sensilla that output a spike only in response to signals of interest. The engineered sensor outputs a discrete analog signal representing strain thresholds. A kinematic model of the sensor design is developed and describes the measured strain in terms of the sensor’s geometric parameters. This model is used to understand trade-offs between sensor resolution and range, and is validated using a finite element model (FEM) of the sensor. The sensor was designed with ease of fabrication in mind, using simple techniques and commercially available components. Fabricated sensors were tested in a four-point flexural test, and the data from the analytical and FEM model show good agreement with the experimental results. The sensors demonstrate resolutions of 83, 158, and 281 microstrain for the different designs tested. A sensor is placed on a model wing to illustrate future applications to MAVs as well as the sensor’s ability to sense both compressive and tensile strains.