[Johnie]

This reminds me of:

>The missile knows where it is at all times. It knows this because it knows where it isn't. By subtracting where it is from where it isn't, or where it isn't from where it is (whichever is greater), it obtains a difference, or deviation

https://knowyourmeme.com/memes/the-missile-knows-where-it-is

[enva2712]

https://www.youtube.com/watch?v=c8jWx2qmBWI

[TaylorAlexander]

the missile is eepy https://youtu.be/Csp_OABIsBM

[CasperH2O]

Up to a point that text makes a lot of sense for describing a PID controller, which is a form of control that only really looks at error and tries to get it to zero.

[constantcrying]

>a PID controller, which is a form of control that only really looks at error

As the name implies the PID controller relies on proportional, integral and derivative information about the error. What you mean is a purely P controller, which just relies on the error.

Missiles are also not guided by a PID controller, that would be silly. They (or the guidance computer in the airplane) has to take into account the trajectory of the target and guide the missile in a way to intercept that target, which is not something you can accomplish with just a PID controller.

[notfish]

It wouldn’t surprise me at all if early heat seeking missiles used just a PID controller, since a big part of what makes PID attractive is the ability to implement it with electrical components. Take a pair of IR photodiodes and wire them such that their difference is the error of your PID control, wire the output of the PID to the steering on your missile, and suddenly you have a missile that points at the nearest IR target (on one axis of course).

Modern missiles do better than this, but a missile wired this way with a proximity fuse would hit the target a reasonable amount of the time. Not silly at all if you haven’t invented microcontrollers yet.

[constantcrying]

"Although proportional navigation was apparently known by the Germans during World War II at Peenemu¨nde, no applications on the Hs. 298 or R-1 mis- siles using proportional navigation were reported [2]. The Lark missile, which had its first successful test in December 1950, was the first missile to use pro- portional navigation. Since that time proportional navigation guidance has been used in virtually all of the world’s tactical radar, infrared (IR), and television (TV) guided missiles [3]. The popularity of this interceptor guidance law is based upon its simplicity, effectiveness, and ease of implementation. Apparently, proportional navigation was first studied by C. Yuan and others at the RCA Laboratories during World War II under the auspices of the U.S. Navy [4]."

From Tactical and Strategic Missile Guidance Sixth Edition.

(To preempt the confusion. Proportional navigation isn't a simple P controller, the missile is seeking an intercept path)

>Not silly at all if you haven’t invented microcontrollers yet.

Apparently the Germans did try that during WW2, but such a missile can not be effective, outside of e.g. bomber intercept.

The "magic" of the AIM-9 Series is that it could achieve this without micro controllers.

[Jerrrry]

  >The "magic" of the AIM-9 Series is that it could achieve this without micro controllers. 

The real magic were the fearless carrier pigeons and self-less kamikaze fighter pigeons missileers.

[snypher]

PID or even just PI are often used to control missile airframe roll rate. Pitch and yaw may be more advanced systems, sure.

[bitwize]

I've observed that hacker culture exists because DARPA funded institutions like MIT for AI research, because the military wanted the missile to know where it is.

[Sakos]

This is almost weirdly philosophical. I've been thinking about this all morning.