3 ms·

Seemed a decent if over-long article to explain something I needed to know about feedback theory. Summary: to do x you may have to do, or briefly get, anti-x wh

Seemed a decent if over-long article to explain something I needed to know about feedback theory. Summary: to do x you may have to do, or briefly get, anti-x which you need to be aware of and account for. Key sentence where the importance clicked for me was: "Let’s say our airplane is running in auto-pilot. We’ve sent a request to gain altitude, so the flight controller tilts the elevators to initiate a climb. But suddenly the airplane is losing altitude, moving farther away from our target? Do we pull up even harder?" It's ok.

padolsey 4y ago
So, to me, this is just calibrating against a continuum. Right? I think of this as binary-searching a kinda normal'ish distribution? I'm not good at math so I had a hard time once the OP article got into differential equations
noduerme 4y ago
I mean, to a layman like myself, the takeaway is something about stateful, irreversible systems where x is on both sides of the equation in unequal or inverse measures, and how those systems (maybe? sometimes?) progress toward equilibrium by going through unexpected phases that seem to contradict what you're trying to input. I read the whole thing as a metaphor for Fed policies or how we elect Democrats every time the economy is about to crash, and Republicans every time it's just recovered. To the degree that some field of math can be best exemplified by various types of aircraft stalls, this didn't do a great job of explaining either the types of stalls or the feedbacks (what you might call negative REPL loops) leading to them. I agree it's ok.
jokabrink 4y ago
Fair enough, but then he wouldn't have needed to use control theory and just stuck with the examples. Edit: removed ambiguity
kubanczyk 4y ago
Talk about a borked example. First of all, I'd call airplane/plane an "aircraft" instead, not because that's what aviators and Wikipedia editors do, but because it's super confusing in an article about some other thing called "plane". And, as an aviator would probably tell you, in order to climb you should care more about the throttle (i.e. increase power) than about them elevators! So, in many cases there is absolutely no such dip. And, I know of no aircraft capable of achieving that loopy flight path using just elevators. That would require quite a bit of kinetic energy, to say the least. The bike counter-steering example clicked instantly with me, but I guess not many people have an intuition about that. I rode for decades before learning this and I think most other cyclists are not aware as well. (Most motorbike instructors teach that however.)
- brandmeyer 4y ago
  > And, as an aviator would probably tell you, in order to climb you should care more about the throttle (i.e. increase power) than about them elevators! So, in many cases there is absolutely no such dip. An autopilot responds the same way, where an altitude error input affects the throttle control. (wincing... when implemented with classical SISO controls...).
- Sohcahtoa82 4y ago
  > The bike counter-steering example clicked instantly with me, but I guess not many people have an intuition about that. I rode for decades before learning this and I think most other cyclists are not aware as well. Veritasium did a video on this: https://youtu.be/9cNmUNHSBac https://youtu.be/9cNmUNHSBac

padolsey 4y ago

So, to me, this is just calibrating against a continuum. Right? I think of this as binary-searching a kinda normal'ish distribution? I'm not good at math so I had a hard time once the OP article got into differential equations

noduerme 4y ago

I mean, to a layman like myself, the takeaway is something about stateful, irreversible systems where x is on both sides of the equation in unequal or inverse measures, and how those systems (maybe? sometimes?) progress toward equilibrium by going through unexpected phases that seem to contradict what you're trying to input. I read the whole thing as a metaphor for Fed policies or how we elect Democrats every time the economy is about to crash, and Republicans every time it's just recovered. To the degree that some field of math can be best exemplified by various types of aircraft stalls, this didn't do a great job of explaining either the types of stalls or the feedbacks (what you might call negative REPL loops) leading to them. I agree it's ok.

jokabrink 4y ago

Fair enough, but then he wouldn't have needed to use control theory and just stuck with the examples. Edit: removed ambiguity

kubanczyk 4y ago

Talk about a borked example. First of all, I'd call airplane/plane an "aircraft" instead, not because that's what aviators and Wikipedia editors do, but because it's super confusing in an article about some other thing called "plane". And, as an aviator would probably tell you, in order to climb you should care more about the throttle (i.e. increase power) than about them elevators! So, in many cases there is absolutely no such dip. And, I know of no aircraft capable of achieving that loopy flight path using just elevators. That would require quite a bit of kinetic energy, to say the least. The bike counter-steering example clicked instantly with me, but I guess not many people have an intuition about that. I rode for decades before learning this and I think most other cyclists are not aware as well. (Most motorbike instructors teach that however.)

brandmeyer 4y ago
> And, as an aviator would probably tell you, in order to climb you should care more about the throttle (i.e. increase power) than about them elevators! So, in many cases there is absolutely no such dip. An autopilot responds the same way, where an altitude error input affects the throttle control. (wincing... when implemented with classical SISO controls...).
Sohcahtoa82 4y ago
> The bike counter-steering example clicked instantly with me, but I guess not many people have an intuition about that. I rode for decades before learning this and I think most other cyclists are not aware as well. Veritasium did a video on this: https://youtu.be/9cNmUNHSBac https://youtu.be/9cNmUNHSBac