Improving PID Recovery from Limit Conditions

This paper addresses the performance of the PID under startup or during normal operation when the PID output becomes limited. Common techniques that have been utilized to reduce the time required to get to setpoint during process startup are reviewed. The response of the PID to conditions that limit PID operation during normal operating conditions is discussed for different implementation approaches. In particular under limiting conditions, anti-reset windup is automatically activated when a positive feedback network is used to create the reset contribution. For such implementations, the recovery from a process saturation condition may be improved by modifying the PID operation. An application example is used to show the impact of this modification on response speed and overshoot.