Sensing, Actuating and Controlling
PID Control
15 min · 2 worked examplesFree
The three terms, what each actually does, and a tuning method that is not guesswork.
After this lesson you can
- Say what each of the three terms responds to
- Tune a loop in a sensible order
- Recognise integral windup and stop it
The three terms
A PID controller computes an error, target minus measurement, and sums three responses to it.
Proportional acts on the error now. Larger error, larger correction. On its own it leaves a steady-state offset, because as the error shrinks so does the effort, and it settles where the remaining push balances the load.
Integral acts on the accumulated error over time. Any persistent error keeps building the integral until it is driven out, which is what removes that offset.
Derivative acts on the rate of change of error. It responds to how fast you are approaching the target and applies the brakes early, damping overshoot.
Output = Kp·e + Ki·∫e + Kd·(de/dt), which is the calculus lesson doing an entirely practical job.
In the full lesson
- The three terms
- Tuning
- Integral windup and practicalities
Free with an account. Read it, work the examples, answer the questions, then build it in the simulator.