A Control-Loop Performance Monitor

A procedure for automatic monitoring of control-loop performance is presented. The control loop performance monitor (CLPM) detects oscillations in the control loop. These oscillations are normally caused by too-high friction in the control valve, but there are other reasons as well. The CLPM is primarily intended to be connected to PID controllers, but it can also be connected to other controllers. The procedure is automatic in the sense that no additional parameters except the normal controller parameters have to be specified. The paper contains both a derivation of the CLPM and results from industrial experiments