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Evolved antenna

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Re: Evolved antenna

#61
post #7

Reminds me of an old article about evolutionary circuit design. The computer was tasked with creating a osscilator using physical hardware. It created a really complex and unconventional design that no-one understood, but it worked, only not work outside of the lab. As it turned out the algorithm had designed it in a way that it used the radio noise from the computer it was running on as a source. It had effectively…

This is the origin of that story. From The Evolved Radio and its Implications for Modelling the Evolution of Novel Sensors "It seems that some circuits had amplified radio signals present in the air that were stable enough over the 2 ms sampling period to give good fitness scores. These signals were generated by nearby PCs in the laboratory where the experiments took place." https://people.duke.edu/~ng46/topics/evolv…

There have been quite a few papers on this probem. If you don't get your simulator AND your cost function right ... fun things happen. Things you probably didn't intend. Last year someone made a compilation paper about a series of fun techniques algorithms have used to satisfy the demands of their creators ... while not solving the problem. It was featured in popular mechanics.

https://www.popularmechanics.com/technology/robots/a19445627...

The way to solve it is something engineers hate for some reason. You explicitly design (and simulate) VERY bad hardware. What's bad hardware ? A camera that has a noise floor of 30% it's measurements. Yes, even in low light conditions (also: noise floor must vary a lot between runs of the algorithm). An actuator that goes the right way 90% of the time, and the result of a particular voltage on the motor varies by 20-30%. And in 10% of cases, it's just entirely stuck, without giving any feedback abou tthat.

https://arxiv.org/pdf/1804.10332.pdf

Or for the more visually inclined: https://www.youtube.com/watch?v=lUZUr7jxoqM

The lesson is that what engineers always do, open-loop designs (I send voltage, motor moves), can be incredibly outperformed in control, accuracy, resiliency, and more by much worse hardware closed-loop designs (I send voltage, motor moves, I check how it moves, I change voltage).

And yet somehow people seem to have incredible issues trusting such systems. For instance, autopilots are mostly open-loop designs. That's like a pilot flying a plane with his eyes glued shut, and no sense of balance (ie. he HAS to trust one instrument, and have no way to verify that, say, the plane actually goes up when they pull the stick. So if it's keeling over backwards or something, they'd just keep pulling the stick right up to the point they hit the decor). They implicitly trust the plane does what the autopilot orders it to do. If for some reason it doesn't ... it's not going to end well.

The issue is that closed-loop designs are much harder to write. The solution to that of course is to not write them, learn them. An autopilot that flies a plane, and when the plane breaks, rapidly learns how to fly a broken plane rather than just trusting it's (now inaccurate) model and killing everyone doing that.

Re: Evolved antenna

#62

Earlier quoted context omitted.

There's a reason that conventional design uses models that abstract away the particulars -- in this case the evolved solution isn't robust to process variation in the FPGA. It's really easy for optimization to exploit irrelevant details to give you designs that aren't very useful. I'm no skeptic when it comes to EAs -- I did my dissertation using them, and I've subsequently written one of my own -- but you have to ha…

Are you aware of anyone who has recreated the process, except with a large pool of different FPGAs from different manufacturers and running designs on a random one each time? I'd imagine with even a moderate pool (~10?) the variation falls away and you're left with a robust design, although the process will take significantly longer.

At that point, why not use a HDL simulator? I think that would be the best approach anyway. The constraint that the circuit can only rely on behavior that can be described by a HDL is a good thing.

Re: Evolved antenna

#63

Earlier quoted context omitted.

Are you aware of anyone who has recreated the process, except with a large pool of different FPGAs from different manufacturers and running designs on a random one each time? I'd imagine with even a moderate pool (~10?) the variation falls away and you're left with a robust design, although the process will take significantly longer.

At that point, why not use a HDL simulator? I think that would be the best approach anyway. The constraint that the circuit can only rely on behavior that can be described by a HDL is a good thing.

I'm getting well out of my domain here, but I'm wondering if there's some "common non-idealness" in FPGAs to be exploited which isn't accurately captured in simulators.

Things like this:

> A further five cells appeared to serve no logical purpose at all--there was no route of connections by which they could influence the output. And yet if he disconnected them, the circuit stopped working.

> It appears that evolution made use of some physical property of these cells--possibly a capacitive effect or electromagnetic inductance--to influence a signal passing nearby. Somehow, it seized on this subtle effect and incorporated it into the solution.

which could be implemented in a more general manner and don't rely on the peculiarities of a single board. It may not prove to be robust, but in a pure research sense I'd love to see it.

Re: Evolved antenna

#64
post #49
post #43

Earlier quoted context omitted.

One of my high-school science-fair projects was a fractal high voltage insulator. The idea was that since high voltage follows the surface of an object, why not give it a lot of surface to run out of energy on? I failed of course - the ceramic was too hard to work (I dulled so many saw blades). And I didn't have an oven to bake it at the required temperature profile, nor a high-voltage lab to test my designs. But a c…

You want a shere/distance/minimize maximum curvature.

An unanswered question was whether the voltage would just jump across the edges of the fractal or follow the surface of the ceramic. Which would likely vary with humidity. I'm sure that General Electric & Siemens test in all kinds of weather conditions - another thing I couldn't do. ;)

Re: Evolved antenna

#65
post #4
post #2

They say this is only used rarely. I’m curious why people wouldn’t design every antenna this way

I do a lot of antenna design. There are far too many variables for optimization, and also size/geometry constraints. That's not to say you wouldn't start with a base design and use an optimizer (which could be genetic). There was a company commercializing this exact algorithm several year ago. I don't think it went anywhere.

Genetic optimisers don't tend to do well over a few hundred parameters, but stochastic gradient descent does well up to billions of parameters as long as you have sufficient compute and ram. Obviously your fitness function needs to be differentiable with respect to the parameters, which most simulators can't yet do.

Re: Evolved antenna

#66

Earlier quoted context omitted.

At that point, why not use a HDL simulator? I think that would be the best approach anyway. The constraint that the circuit can only rely on behavior that can be described by a HDL is a good thing.

I'm getting well out of my domain here, but I'm wondering if there's some "common non-idealness" in FPGAs to be exploited which isn't accurately captured in simulators. Things like this: > A further five cells appeared to serve no logical purpose at all--there was no route of connections by which they could influence the output. And yet if he disconnected them, the circuit stopped working. > It appears that evolution…

As dnautics alludes in a sibling commment, the effect you're talking about is subtly floorplan dependent, and that's going to vary from manufacturer to manufacturer. I don't think it's completely impossible that there's a common non-idealness to FPGAs, but I also don't think that the common non-idealness is going to involve using disconnected cells as some kind of antenna.

Re: Evolved antenna

#67
post #60

Earlier quoted context omitted.

Evolutionary algorithms are just a variation of pseudo-random search.

Sophisticated is (also) a synonym of convulted.

All of us are products of evolution. Either you are sophisticated or convoluted. Choose.

Re: Evolved antenna

#68
post #55
post #54

I accidentally "evolved" a microwave antenna in my microwave oven, once. I put some hematite sand on the top of a glass plate that was suspended about 5 inches from the bottom of the microwave oven. I wanted to see what kind of pattern the standing waves would heat the hematite to (this microwave didn't have an RF stirring fan). Instead of some standing wave pattern, I ended up with a fractal like antenna that grew f…

I would love to see pictures or a video of this in action!

Sounds like a Star Trek episode: a creature evolving to avoid weapons, morphing into something unstoppable.

Re: Evolved antenna

#69
post #55
post #54

I accidentally "evolved" a microwave antenna in my microwave oven, once. I put some hematite sand on the top of a glass plate that was suspended about 5 inches from the bottom of the microwave oven. I wanted to see what kind of pattern the standing waves would heat the hematite to (this microwave didn't have an RF stirring fan). Instead of some standing wave pattern, I ended up with a fractal like antenna that grew f…

I would love to see pictures or a video of this in action!

I don't have a video, and I can't find the original picture, but here's a very low resolution version: https://pbs.twimg.com/profile_images/378800000340843432/c1f1...
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