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chcampb t1_j4qdn3k wrote

"Negative Derivatives" -> Integrals? Is this a thing? I would just say the integrals of position, in the same way jerk is the derivative of acceleration. I have heard "anti-derivative" as well.

Pipe organs and other flow based instruments were the examples I remember from when I last looked up uses for absement. The volume is based on the position of a key, which allows flow to build up in a pipe, which is proportional to how far down the key is pressed (ie, the integral of key position).

This was posted in a similar question and has a lot of good info, except for the 2nd integral of position except to say that there is a two staged absement instrument (so, what would be the sound output actually controls the "key" for the next stage of the pipe...). It's pretty contrived.

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Coomb t1_j4rnv31 wrote

The obvious application is that if you want to design a control circuit for something that's able to move around and you want to be able to tell it to remain in a specific place, you use a PID controller to actuate whatever it uses to move itself. PID stands for "proportional, integral, derivative".

In the case of trying to maintain the same position, one part of the decision of how hard to try to move in a particular direction would be how far away you are from your set point at that instant. That's your proportional control. If you're really far away, you probably want to push pretty hard to get back so that you can spend more time at your set point. Another part of the decision of how hard to try to move would be how long you have been away from your set point, and how far you were over that time (you probably want to push harder to get back to your set point if you've been very far away for a very long time, but even if you've gotten very close, if you've been away from that set point for a really long time, you need to push a tiny bit harder to get back exactly where you want to be). That's the integral control. And, of course, the derivative control is obvious: if you're away from your set point and your velocity is still in a direction away from your set point, you definitely need to push harder back towards your set point.

The integral component here is reliant on absement.

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rededelk t1_j4rzih6 wrote

Would I be wrong to simplify and say a PID loop is more or less an if this, then that algorithm? I don't do industrial process control programming (but am thinking about it) I do have to manipulate user inputs via the hmi and I understand coding and work with paid and open source process control programs. (looking for a career change). Thanks

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BobGeneric t1_j4slwpb wrote

A pure PID control is more of a calculation than an "if this than that" algorithm. There are different implementations, but at the end it's like output=errorKp + Kdd(error)/dt + Ki*integral(error)dt, where Kp, Kd and Ki are constants tuned to the system to be controled. This output is applied to an actuator that changes the system, and the objective is to zero the error. The PID control was originally a full analog circuit, done with operational amplifiers, so, no if/elses...

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Coomb t1_j4s0nub wrote

Every algorithm is a set of "if this, then that" steps. That's the definition of an algorithm. Why are you asking this question? Do you have a more specific question?

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