Data processing: generic control systems or specific application – Generic control system – apparatus or process – Optimization or adaptive control
Patent
1998-04-03
2000-06-27
Palys, Joseph E.
Data processing: generic control systems or specific application
Generic control system, apparatus or process
Optimization or adaptive control
700 39, 700 52, 700 72, G05B 1136
Patent
active
060817518
ABSTRACT:
A system and method for automatically tuning a PID controller resident within a PID control loop. The PID control loop includes a PID controller and a process. The process supplies a process variable which is compared to the loop input. The result of the comparison is supplied to the PID controller, and the PID controller drives the process. A relay is applied to the loop input. The relay compares a set point value to the process variable. If the set point value is greater than the process variable, the relay drives the loop input with a first amplitude value. If the set point value is less than the process variable, the relay drives the loop input with a second amplitude value. In response to the set point relay, the process variable develops a sustained oscillation. The period and amplitude of the sustained oscillation are measured. A new set of PID controller parameters are calculated from the period and amplitude of sustained oscillation. In particular, the oscillation period and amplitude are used to calculated a time constant and dead time for a standard process model. The time constant and dead time are used to calculate the new PID controller parameters either (a) directly through the formulae associated with the Ziegler-Nichols reaction curve method, or (b) through the intermediate step of calculating an ultimate period and frequency from the time constant and deadtime.
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Tor Steinar Schei, "A Method for Closed Loop Automatic Tuning of PID Controllers", 1992, International Federation of Automatic Control, pp. 587-591.
Chen Dapang
Luo Rongfu
Qin S. Joe
Hood Jeffrey C.
Mai Rijue
National Instruments Corporation
Palys Joseph E.
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