A Soft Material Flow Sensor for Micro Air Vehicles

Abstract

To control and navigate micro air vehicles (MAVs) efficiently, there is a need for small, lightweight, durable, sensitive, fast, and low-power airspeed sensors. When designing sensors to meet these requirements, soft materials are promising alternatives to more traditional materials due to the large deformations they can withstand. In this article, a new concept of a soft material flow sensor is presented based on elastic filament velocimetry, which fulfills all necessary criteria. This technique measures flow velocity by relating it to the strain of a soft ribbon suspended between two static supports and subjected to a flow of interest. The ribbon is manufactured from polydimethylsiloxane and can be made piezoresistive by the addition of silver nanowires. With the described manufacturing method, the sensor can be made using common laboratory tools, outside of a clean room, significantly reducing its complexity. Furthermore, it can be operated using a simple and lightweight circuit, making it a convenient alternative for MAVs. Using a piezoresistive material allows for the flow velocity to be calibrated to the resistance change of the strained ribbon. Although certain challenges remain unsolved, such as polymer creep, the sensor has demonstrated its ability to measure flow velocities down to 4 m/s in air through experiments. A time-dependent analytical model is also provided. The model shows that the current sensor has a bandwidth of 480 Hz. Most importantly, the sensitivity and the bandwidth of the sensor can be varied strictly by modifying the geometry and the material properties of the ribbon.

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“…It means that our mesh-type film sensor can work in a tremendous bandwidth from 200 Hz to 10 kHz, which is wider than those of the published works (see Table ). ,,,− This high performance of our acoustic sensor is related to the designed regular mesh pattern, giving rise to the larger contact area with the airflow. Besides, the film sensor is also able to clearly discriminate two sound signals with very closer frequencies, like 380.00 and 380.05 Hz, as shown in Figure e,f.…”

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“…Motivated by the challenges with conventional airflow sensors, there have been efforts to develop custom airflow sensing technology for multirotor drones. For example, flow speed (but not direction) can be estimated by measuring the deflection of a single sensing element [20], [21]. The whisker-like sensors used in [22] can resolve airflow direction from deflection using multiple sensing elements; however, [22] does not provide a characterization of the temporal characteristics (lag and frequency) of the sensors.…”

Smart Chemical Engineering‐Based Lightweight and Miniaturized Attachable Systems for Advanced Drug Delivery and Diagnostics

“…[ 24 ] Intriguingly, the hair‐like structures pick up flow motion to measure both the direction and velocity based on the influence on the drag forces. [ 25 ] In crickets, there is a single sensory cell below the hair shaft, whereas spiders or fishes have several cells, which facilitates flow movement detection. [ 26 ] Similarly, the tiger wandering spider ( cupiennius sale i) possesses this kind of cilia on its legs, which translates the drag force induced by the flow to mechanical bending, eliciting an electrical impulse across the hair cell membrane located at the base of the cilia.…”