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Comment by riotnrrd | Hacker News Reader

I used to work in perception for autonomous aerial vehicles and horizontal wires were the hardest common object to avoid. Traditional stereo won't help you localize them -- wires are thin so even mere detection can be hard, and one portion of a wire looks much like another so feature matching fails resulting in bad or no depth estimates -- and LIDAR sacrifices resolution for weight and power consumption (which both have to be optimizied for drones). It's been years since I've worked in this field, and Amazon has many smart people thinking about it but I'm not surprised it's still a difficult problem.

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> 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.

Would help avoid damage with other misrecognized or ignired objects, too.

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.

> 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.

I don't think you read my entire comment, or perhaps you're very unfamiliar with the operation of a PS3's analog control.

(The whisker can be both rigid and also flexibly-attached. These are not mutually-exclusive constructs.)

Here, suppose you've got a rigid sensor attached to your hand by a string of yarn.

You walk in one direction, then turn around and start walking in a different direction, but as you turn the sensor slams into something.

Does it fail to take damage because the yarn is flexible?

Huh?

Suppose I've got an assembly with a chopstick attached to a gimbal with some minor centering springs and sensors (potentiometers) inside. The chopstick has many degrees of free angular movement provided by this gimbal and overall assembly.

I gently bounce ("slam"?) that chopstick off of a thing, and this results in the feedback loop that provides positioning control to provide immediate instruction to back off in the opposite direction of the apparent impact.

Does the chopstick take damage? Does the gimbal take damage? Does the greater assembly take damage?

Why, or why not?

(I feel like we're speaking two different languages here. Have you ever looked at how a PS3 analog stick works, or have you not? It's not new tech. It wasn't even new when it was new, and it's very nearly 20 years old now in PS3 form.)

> I gently bounce ("slam"?) that chopstick off of a thing

Hey, remember when I said this?

>>>> Think of the rigidity of the whiskers as being traded off against your maximum movement speed.

Appendages on a moving object can't contact anything gently. They have to strike at whatever speed they're moving at.

Yes, you've successfully confirmed: We're quite clearly speaking different languages.

(Good luck with...whatever it is that you may be talking about. My diction is good. I don't have time or patience to explain it for outliers who aren't following along well and who also insist that it must somehow be wrong. I apologize for this; I am actually sorry.)

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.

Slow down.

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

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.

Ah yeah I came up with the solution to that one. It's 'don't fly drones over our heads' approach. Also the 'upgrade the fragile infrastructure so a light breeze doesn't take out millions of people's power.'

Sorry, not profitable enough, not a "team player". Please enjoy these weekly 1:1s with your manager and HR.

It’s really hard for people too. The advice I got for landing in a field was to assume that every pole you saw had wires going to every other pole. Which is reasonable enough for that scenario, but not workable for continual low altitude flying in a built up area.

> horizontal wires were the hardest common object to avoid... Traditional stereo won't help you localize them

This makes a lot of sense. I wonder if it wouldn't be better for autonomous vision to use three cameras instead of two for better spatial reasoning.. maybe in a triangle pattern?

We experimented with a rig with more cameras on it (four, in a square) but the baseline of the cameras on the drones we were using could be measured in centimeters, so the vertical stereo pairs didn't provide much better results. Further, more cameras means more power, more weight, and much more expensive on-board processing (which also will require more power).

Definitely tough. mmWave radar is useful for this use case; I know Amazon were testing it on earlier drones but I'm not sure if they still use it.

Cables don't move often. Why not simply have a map of all of them?

Google sell maps of things like this from street view data.

All cables? Everywhere in the entire country? Accurate to the centimeter level and updated on the hour?

Edit: This was flippant, but the real issues are: any map you get will be incomplete and obsolete almost immediately and cables move and sway in the breeze.

It doesn’t need to be at the cm level. Giving them a 10m berth should be fine.

A 10m berth from wires would exclude a substantial proportion of houses in my city.

Then they shouldn’t be flying in your city.

As is apparently becoming obvious.

I can’t think of a major city I’ve been to on earth where 10M from a hung cable is realistic outside of some suburbs and rural areas.

    > I can’t think of a major city I’ve been to on earth

Does Manhattan count? I am pretty sure south of 96th street has no above ground utilities.

OpenStreetMap supports annotating poles and theirs cables. It's common for power lines (local and long distance). There are also annotations for communication lines (https://wiki.openstreetmap.org/wiki/Tag:communication%3Dline).

There are also public and proprietary "aviation obstacle" databases across the world.

Any one particular cable might not move often, but if a telco owns N bucket trucks it's a safe bet that about N cables move every workday.

Telcos are notoriously secretive about the location of their fiber. They even got most state legislatures to exempt it from state-level FOIA laws.

If you have a map of all utility poles you could probably just avoid every straight line between any of them within some reasonable distance of eachother.

it's an approximation of dangerous areas, catenary curves are more accurate than straight lines but you don't know the length of the cable so you don't know the droop height.

OpenPoleMap is achievable. Just don't expect local governments to subsidise the mapping of obstacles to drones of the likes of Amazon.

Most "utility pole maps" only show poles with power lines on them.

A ton of telco cables are on telco-only poles (basically just a really straight tree trunk shoved in the ground, no cross-arms at all).

> Traditional stereo won't help you localize them

Wouldn't making a quick circuit around the house before landing allow wires to be observed from multiple angles be enough?

Yes but tradeoffs with delivery speed, and thin wires are still hard to detect with limits on vision processing.

Helicopter pilots have trouble with them as well.

It's very simple: don't fly there

there are very little aerial lines few meters highers and ones that exist can be probably spotted from satellite images and planned around.

Especially if delivery area is limited, they could just map them out of the routes.

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