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Re: What is P.I.D.?
A layman's explanation of the 3 tuning parameters: P, I, D.
CP = current position of your mechanism
TP = target position of where you want the mechanism
P term is a how far your CP is away from the TP, the farther it is (the longer that distance), the faster this will drive your mechanism to move towards TP.
I term is the length of time, how long your mechanism has been taking to get from the "beginning of time" (when you turned on the PID algorithm and gave it the TP) to now... the longer that time is, the faster this will drive your mechanism to move toward TP.
D term is how quickly the mechanism has been closing the distance between CP and TP. The faster the distance is being closed, D will try to slow down this rate.
There's a general problem in any mechanical and sensor system in that there are always a delays in the system - delays in issuing the motor output signal to the motors actually responding and changing speed; delays in the sensors measuring distance/turns and feeding it back to the computer... By the time you've made the measurement and gotten it into the computer and your program, the mechanism has already moved on to some place else...
In this end, some system lead to overshoot and oscillation... Depending on what you need, whether your mechanism can accept overshoot and oscillations, that is the goal of a properly tuned PID system, to get your mechanism from CP to TP at the speed that you desired (or the amount of time desired) without much (or any) overshoot or oscillations...
It gets harder if you allow the TP to change mid-travel. It also gets harder if there is a lot of noise in the sensor system.
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