Integral windup, also known as integrator windup[1] or reset windup,[2] refers to the situation in a PID controller where a large change in setpoint occurs (say a positive change) and the integral term accumulates a significant error during the rise (windup), thus overshooting and continuing to increase as this accumulated error is unwound (offset by errors in the other direction).
This problem can be addressed by Integral windup particularly occurs as a limitation of physical systems, compared with ideal systems, due to the ideal output being physically impossible (process saturation: the output of the process being limited at the top or bottom of its scale, making the error constant).
In this case, anti-windup can actually involve the integrator being turned off for periods of time until the response falls back into an acceptable range.
Integral windup was more of a problem in analog controllers.
Within modern distributed control systems and programmable logic controllers, it is much easier to prevent integral windup by either limiting the controller output, limiting the integral to produce feasible output,[5] or by using external reset feedback, which is a means of feeding back the selected output to the integral circuit of all controllers in the selection scheme so that a closed loop is maintained.