US 5,331,541 AGranted

PiD control unit

AssigneeOMRON Corporation

InventorsTamio Ueda, Yoshihiro Nagami, Yumi Saito, Zhang Zhiming

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Abstract

A PID control device identifies rise characteristics of a controlled system by a step response method on changing a reference, moves to PID control when idle time and slope successively obtained at the rise reach a predetermined condition, and computes PID control parameters based on the idle time and slope obtained up to that point. If the identification is fully executed, the computed PID control parameters are immediately set. If it is not fully executed, the PID control device 1 further watches the state to compare a proportional gain of the newly computed PID control parameters with the proportional gain of previously set PID control parameters, and the currently computed PID control parameters are set when the parameters are on a safe side.

Claims4

Dependent claims

A self control type PID control unit for controlling a controlled system comprising:

step manipulated variable output means for outputting a step manipulated variable,
PID control means for generating a manipulated variable based on an error between a reference and a controlled variable obtained from the controlled system,
control mode switching means for applying said step manipulated variable to the controlled system and for stopping the application of the step manipulated variable to move to PID control by said PID control means when idle time and slope successively obtained in accordance with a change of said controlled variable reach a predetermined condition,
identification means for successively computing by a predetermined sampling period the idle time and the slope according to a change of the controlled variable by a step response of the controlled system applied by the step manipulated variable to provide an output, and
setting means for computing PID control parameters based on said idle time and said slope computed by said identification means after reaching said predetermined condition to be set to said PID control means.

2 more elements

Dependencies are inferred from the claim text.