Traditional PID Control Strategy

PID control is applied to loops that typically have fast response times. Traditional PID control works on error from setpoint. For example, in a forehearth, a sensor is placed at the exit of each forehearth zone to measure glass temperature as it exits the zone. The sensor relays data to a PID controller, which adjusts the heat in an attempt to bring the glass temperature back to setpoint. As the molten glass travels through each forehearth chamber, respective controllers continue to “play catch up.” The result tends to be a lengthy recovery time, during which production values decrease.

PID control loops for the system rely on the process interrelationships between Proportional (P), Integral (I), and Derivative (D) variables; the interaction between these three control elements enables a response from the PID controller appropriate to the current process situation.

PID control works well under steady state conditions; however, such loops are extremely difficult to tune, and operators typically do not see the types of reaction times they desire for job changes. it may be necessary to implement Model Based Control to overcome these difficulties or to enhance parts of your system.