Self-tuning controller

Claim 2

The method of claim 1, wherein said step of combining includes producing an overshoot value as one of said set of performance characteristics.

Claim 3

The method of claim 1, wherein said step of combining includes producing a decay value as one of said measured performance characteristics.

Claim 4

The method of claim 1, wherein the step of measuring the amplitudes includes locating and measuring a knee of said error signal, later in time to a first local extremum.

Claim 5

The method of claim 1, further including the step of measuring an error noise and updating a noise band during a quiet state of said error signal.

Claim 6

The method of claim 1, further including the step of filtering said set-point signal with a lead-lag filter to prevent an excessive error overshoot in response to a set-point change when the controller is well tuned for a load upset.

Claim 9

The method of claim 7, wherein said calculated decay characteristic value is equal to a measured noise band divided by the amplitude of the first peak minus the amplitude of the knee value.

Claim 12

The method of claim 9, further including the steps of estimating a third amplitude value and selecting a decay characteristic value determined from the smaller of a target decay value or a calculated decay value using said amplitudes.

Claim 13

The method of claim 9, wherein the step of measuring amplitude values includes measuring at least four successive amplitude values of local extrema of said error signal.

Claim 14

The method of claim 11, wherein the step of measuring amplitudes includes estimating said fourth amplitude value if said fourth amplitude value cannot be measured.

Claim 15

The method of claim 9, further including the steps of measuring a third amplitude value and calculating a decay characteristic.

Claim 16

The method of claim 13, wherein the step of measuring amplitudes further includes the step of selecting three successive amplitude values to produce the overshoot characteristic and the decay characteristic, wherein said measured decay characteristic is greater that said overshoot characteristic.

Claim 17

The method of claim 14, wherein said amplitude values are local extrema of said error signal.

Claim 18

The method of claim 9, wherein the step of measuring the second amplitude value includes locating a knee of said error signal later in time to said first amplitude value.

Claim 19

The method of claim 16, further including the step of determining the period between the first amplitude and said knee to determine a time scale of the error signal response.

Claim 20

The method of claim 17, wherein said time scale is used to determine a length of time for searching for a second extremum.

Claim 21

The method of claim 17, wherein said time scale is used to determine a period for locating and confirming a third amplitude value.

Claim 22

The method of claim 16, wherein the step of measuring the amplitudes includes selecting said knee as said second amplitude.

Claim 23

The method of claim 16, wherein the step of locating said knee of said error signal including locating said knee later in time to said second amplitude value.

Claim 24

The method of claim 9, wherein the step of automatically adjusting includes determining the type of process being regulated and selecting control parameters appropriate to the determined process type.

Claim 25

The method of claim 22, wherein the step of automatically adjusting further includes comparing measured data with interpolated data from at least two predetermined processes to determine an interpolating factor indicative of the type of process being regulated for adjusting at least one of the control parameters.

Claim 26

The method of claim 22, wherein the step of automatically adjusting further includes comparing measured data with extrapolated data from at least two predetermined processes to determine an extrapolating factor indicative of the type of process being regulated.

Claim 27

The method of claim 9, further including the steps of sampling a user-selected process variable before the step of measuring amplitude values and selecting from a previously stored set of control parameters to provide an improved tuning for the present process condition.

Claim 28

The method of claim 25, wherein the time varying process variable is subdivided into subranges in which each subrange corresponds to a set of previously adapted control parameters.

Claim 29

The method of claim 9, further including the step of filtering said set-point signal with a lead-lag filter to prevent an excessive error overshoot in response to a set-point change when the controller is well tuned for a load upset.

Claim 30

The method of claim 27, further including the step of adaptively tuning a ratio of said lag-lead filter to achieve a target overshoot value.

Claim 33

The method as in claim 29, wherein said amplitude values are local extrema of the error signal.

Claim 34

The method as in claim 29, wherein said error signal is equal to the difference between a process variable signal and a set-point signal.

Claim 35

The method of claim 29, wherein the step of automatically adjusting the control parameters includes determining the type of process being regulated and determining changes in the control parameters as a function of the process type.

Claim 36

The method of claim 32, wherein the step of automatically adjusting further includes comparing measured data with interpolated data from at least two predetermined processes to determine an interpolating factor indicative of the type of process being regulated.

Claim 37

The method of claim 33, wherein the interpolated data includes control parameters.

Claim 38

The method of claim 34, wherein the controller parameters include proportional and integral time data.

Claim 39

The method of claim 32, wherein the step of automatically adjusting further includes comparing measured data with interpolated data from at least two predetermined processes to determine appropriate changes in the control parameters.

Claim 40

The method of claim 29, wherein the step of automatically adjusting further includes comparing measured data with extrapolated data from at least two predetermined processes to determine appropriate changes in the control parameters.

Claim 41

The method as in claim 29, wherein the step of locating and measuring amplitude values includes locating and measuring at least four successive amplitude values of local extrema of said error signal.

Claim 42

The method as in claim 38, wherein the step of locating and measuring amplitudes includes estimating said fourth amplitude value if said fourth amplitude value cannot be measured.

Claim 43

The method of claim 39, wherein the step of locating and measuring the amplitudes includes locating a knee of said error signal later in time to a first local extremum.

Claim 44

The method of claim 38, further including the step of determining the period between the first local extremum and said knee to determine a time scale of the error signal response.

Claim 45

The method of claim 41, wherein the first local extremum is selected as the first of three successive amplitude values and said time scale is used to determine a maximum wait period for locating a second amplitude.

Claim 46

The method of claim 42, wherein the step of selecting the amplitude values if said maximum wait period expires before locating a second local extremum.

Claim 47

The method of claim 41, wherein said time scale is used to calculate a maximum wait period for locating a third amplitude.

Claim 48

The method of claim 38, wherein the step of locating said knee later in time to a second local extremum.

Claim 49

The method of claim 38, further including the step of validating the knee of said error signal.

Claim 50

The method of claim 29, further including sampling a user-selected process variable before the step of locating and measuring amplitude values and selecting previously adapted control parameters, based on a sampled value of the user-selected process variable, from a previously stored set of control parameters to provide an improved tuning for the present process condition.

Claim 51

The method of claim 47, wherein the process variable range is subdivided into subranges in which each subrange corresponds to a set of previously adapted control parameters.

Claim 52

The method of claim 29, wherein the step of selecting three successive amplitude values includes indicating the sign of the first amplitude values to determine whether it is positive or negative, and inverting the values of said three amplitude values if the sign of the first amplitude is negative for simplifying the step of measuring said amplitude values.

Claim 53

The method of claim 31, further including the step of filtering said set-point signal with a lead-lag filter to prevent an excessive error overshoot in response to a set-point change when the controller is well tuned for a load upset.

Claim 54

The method of claim 50, further including the step of adaptively tuning a ratio of lead-to-lag of said lead-lag filter to achieve a target overshoot value.

Claim 55

The method of claim 29, further including the steps of measuring an error noise and updating a noise band during a quiet state of said error signal.

Claim 56

The method of claim 29, further including the step of validating the measured amplitude values of local extrema.

Claim 57

A self-tuning control system comprising: a controller having control parameters for regulating a process having a measured process variable signal; means for generating an error signal representing a closed-loop response of the process to an upset condition; and an adaptor for automatically adjusting control parameters of the controller, said adaptor comprising: means for measuring amplitude values characterizing the pattern features of said error signal; means for choosing three successive amplitude values to produce measured decay and overshoot characteristics of said error signal; means for selecting three successive amplitude values wherein said measured decay characteristic is greater than said overshoot characteristic, said selection means comprising the steps of: (i) determining the measured decay and overshoot characteristics of said three successive amplitude values; and (ii) discarding said first amplitude value and locating a new third amplitude value if said measured decay characteristic is not greater than said overshoot characteristic of said three successive amplitude values; and (iii) repeating steps (i) through (ii) until the three successive amplitude values are indicative of said measured decay characteristic greater than said overshoot characteristic; and means for automatically adjusting at least one of the control parameters of the controller to improve the difference between one of said measured characteristics and a target characteristic.

Claim 58

A self-tuning control system comprising: a controller having control parameters for regulating a process having a measured process variable signal; means for generating an error signal representing a closed-loop response of the process to an upset condition; and an adaptor for automatically adjusting control parameters of the controller, said adaptor comprising: means for measuring amplitude values characterizing the pattern features of said error signal; means for choosing three successive amplitude values to produce measured decay and overshoot characteristics of said error signal; means for selecting three successive amplitude values wherein said measured decay characteristic is greater than said overshoot characteristic, said selection means comprising the steps of: (i) determining the measured decay and overshoot characteristics of said three successive amplitude values; and (ii) discarding said first amplitude value and locating a new third amplitude value if said measured decay characteristic is not greater than said overshoot characteristic of said three successive amplitude values; and (iii) repeating steps (i) through (ii) until the three successive amplitude values are indicative of said measured decay characteristic greater than said overshoot characteristic; and means for automatically adjusting at least one of the control parameters of the controller to improve the difference between one of said measured characteristics and a target characteristic.