Designing a Soil Probe

The specifications for my summer internship work have been laid out for me and they’re rather vague, giving me a lot of freedom!

I am to design an acoustic probe to be mounted to a small autonomous drone, to replace by-hand testing in the agricultural industry. They’ve also given me an accelerometer which will be used to record the audio. It’s a proprietary design, 3-axis accelerometer with a very small form factor, currently set in resin, moulded with a medicine capsule casing.

I’ve been directed to a paper by Marine Lacoste which may prove useful, as she also records audio signatures of soil biology but it seems that the main problem I’ll encounter will be how a small low-mass drone will be able to penetrate the soil. It’s summer here and the ground is hard and dry. I’ve been invited to work with a local business in the agricultural science sector and I’ve already seen the large ATVs they use to take soil samples. Since Lacoste uses a buried probe in her paper, it seems this is the way I’m being directed to go as well, but to penetrate the ground like that do a depth of maybe 10cm could prove impossible.

My first thought is to use an auger bit design, to reduce the downward force required to penetrate the soil as I’m hoping the bit will grip the soil and pull itself deeper in. I’ve designed 3D printed a modular auger bit which will hold the sensor, though a drill design means I’ll need some form of slip ring to maintain the sensor’s connections to the recording device. I’ll either have to ditch this or design my own micro slip ring soon enough, we’ll see.

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