Comment by cesarb 2 days ago
> Traditional stereo won't help you localize them [...] and LIDAR sacrifices resolution for weight and power consumption
I wonder if a more mechanical solution wouldn't help:
Whiskers, like on a cat. A long enough set of thin lightweight whiskers could touch the wire before the propellers do, giving time for the drone to stop and change course. Essentially, giving the drone a sense of touch.
Thin lightweight whiskers are going to be challenging to manage on a propeller-driven vehicle. They'll get blown all over the place. Having them extend out past the propellers will likely get them tangled in the propellers.
Sure, they'll move around in the prop wash.
But that's fine, isn't it? If they're intended to detect fixed objects, then noticing that one or more of them have ceased to be blown around in that way may be a good way to detect unanticipated contact with a fixed object: When the signal becomes less noisy, then maybe something is in the way.
And the whiskers don't have to be all floppy like a wet noodle. I myself am thinking that something rigid or semi-rigid might be good. Perhaps something akin to armature wire, or thin spring steel. Maybe even literal bamboo chopsticks.
They can also be constrained so that they don't get sent into the props.
My little brain thinks that the drone-end of the whiskers can be attached to potentiometers, with light return springs to bring them back towards center, like the mechanism used by an analog stick on a PS3 controller.
Rigid whiskers have other sets of problems. Below someone mentioned that rigid whiskers will break when they contact objects. If the whisker is as rigid as the drone itself, it plausibly breaks the same cables that the drone breaks. You also have the problem that in the event of drone failure, you now have a spike-covered drone falling out of the sky. What kind of damage does a bamboo chopstick or thin piece of steel do when it hits someone or something at ground level at drone-falling velocity with the mass of a drone behind it?
It's quite possible that these problems are solvable and can be engineered around, that there's a whisker-based solution, but I don't see it. It's certainly not an obviously workable solution.
> And the whiskers don't have to be all floppy like a wet noodle. I myself am thinking that something rigid or semi-rigid might be good.
I don't think you're right about this. The concept of the whiskers is to notice when you've collided with something. Real whiskers aren't rigid because colliding with something when you're rigid means snapping. (Ever stub your toe?)
Think of the rigidity of the whiskers as being traded off against your maximum movement speed.
A cage around the drone, there are kids toys like this, and also commercial products for inspection. Prevents contact with other objects, contact can be sensed and reacted to. https://www.flyability.com/elios-3
Doesn't protect against everything, like Spanish Moss which dangles from trees, but that is a lot bigger than a long thin wire.
As an undergrad I worked with a professor who was doing precisely that! https://sense-lab.github.io/pubs/pdf/solomon_nature_2006.pdf
I hadn't thought about this in a long time. Looks like her lab is still going strong doing research at the intersection of biology and robotics on whisker-based sensing:
https://sense-lab.github.io/robotics.html
https://sense-lab.github.io/publications.html