title: PID controller - intuition for when error=0
body: <p>I have simulated a PID controller with an input parameter that affects the output, and set Kp=0.2, Kp=0.5, Kd=0 which seemed to work best the values I expect in reality.
  However one thing I could not figure out is the intuition of how the controller starts when the error is 0. I, for example, my target is 2, the output is 2, and the input variable is, say, 4 -  the controller would setthe next input to be 0 - although 4 is a perfect value.</p>
  
  <p>Is there some way that is theoretically sound to make the first steps of the algorithm take into account some "initial guess" and not go way off at the beginning of the process?</p>