System and method for automatically tuning a process controller

Claim 3

The method of claim 1, said determining step comprising: determining, from said at least one output during a first portion of said controlled self-oscillation, said time delay characteristic of said process; and determining, from said at least one output during a second portion of said controlled self-oscillation, said ultimate period characteristic and said ultimate gain characteristic of said process.

Claim 4

The method of claim 1, said applying step comprising, applying a square-wave signal superimposed on a predetermined control signal to said control input of said process.

Claim 5

The method of claim 3, said applying step further comprising: applying a first square-wave signal superimposed on said predetermined control signal for a first portion of said controlled self-oscillation; and applying a second square-wave signal superimposed on said predetermined control signal for a second portion of said controlled self-oscillation.

Claim 6

The method of claim 4, said step of determining said time delay characteristic comprising: detecting a slope of said at least one output during application of said first square-wave signal; and determining said time delay characteristic as a function of said slope.

Claim 7

The method of claim 5, said step of determining said ultimate period characteristic and said ultimate gain characteristic, comprising: measuring, during application of said second square-wave signal, an amplitude and period of said self-oscillation of said at least one output; and calculating said ultimate period characteristic and said ultimate gain characteristic as functions of said amplitude and period.

Claim 8

The method of claim 1, said process controller comprising a PID controller, and said tunable control parameters comprising, controller gain, K c , controller integral time, T i , and controller derivative time, T der .

Claim 9

The method of claim 1, said process being modeled as a first order process with time delay, said tuning step comprising: calculating a time constant of said process as a function of said time delay characteristic and said ultimate period characteristic of said process; determining a static gain of said process; and calculating said values for said tunable control parameters of said controller as a function of said [Time Delay, Time Constant and Static Gain time delay characteristic, time constant and static gain of said process.

Claim 10

The method of claim 8, said step of determining said static gain comprising: applying a perturbation to said control input of said process; measuring a magnitude of a change in said process output due to said perturbation; and calculating said static gain as a function of relative magnitudes of said perturbation and said change.

Claim 11

The method of claim 8, said step of determining said static gain of said process comprising, calculating said static gain as a function of said time delay characteristic, time constant and ultimate gain characteristic of said process.

Claim 14

A tunable control system comprising: a process controller having a process variable input and a controlled variable output, said input and output being adapted for connection to a process to be controlled; a signal generator producing a controllable generator signal adapted for connection to said process to be controlled; and a tuner, connected to said process controller and signal generator, and adapted for connection to said process to be controlled, said tuner including: means for disconnecting said controlled variable output from said process and for connecting said controllable generator signal to said process; means for controlling said signal generator to apply a signal to said process to cause said process to undergo controlled self-oscillation; means for monitoring said process variable during said controlled self-oscillation; means for determining, from a first portion of said controlled self-oscillation, a time delay of said process, and for determining from a second portion of said controlled self-oscillation, an ultimate gain and an ultimate period of said process; and means for calculating control parameters for said process controller, based upon on said time delay, ultimate period and ultimate gain of said process.

Claim 15

A tunable control system comprising: a process controller having a process variable input and a controlled variable output, said input and output being adapted for connection to a process to be controlled; a signal generator producing a controllable generator signal adapted for connection to said process to be controlled; and a tuner, connected to said process controller and signal generator, and adapted for connection to said process to be controlled, said tuner including: means for disconnecting said controlled variable output from said process and for connecting said controllable generator signal to said process; means for controlling said signal generator to apply a signal to said process to cause said process to undergo controlled self-oscillation; means for monitoring said process variable during said controlled self-oscillation; means for determining, from a first portion of said controlled self-oscillation, a time delay of said process, and for determining from a second portion of said controlled self-oscillation, an ultimate gain and an ultimate period of said process; and means for calculating control parameters for said process controller, based upon on said time delay, ultimate period and ultimate gain of said process.