PI controller
In control engineering, a PI Controller (proportional-integral controller) is a feedback controller which drives the plant to be controlled with a weighted sum of the error (difference between the output and desired set-point) and the integral of that value. It is a special case of the common PID controller in which the derivative (D) of the error is not used.
 | This engineering-related article is a stub. You can help Wikipedia by expanding it. |
Controller output = Constant KI x Summation (Error x Time)
Advantages Of a Proportional Plus Integral Controller
A PI Controller is used to remove steady-state errors.
Disadvantages Of A Proportional Plus Integral Controller
The problem with using a PI controller is that it introduces a phase-lag. This means that on a Nichols Plot, the stability margin (the phase margin) decreases. So careful design considerations with respect to the gain must be considered.
Rectifying The Phase Lag
The phase-lag can be countered/rectified by introduces a Proportional plus Differential Controller (PD Controller).