# US 10,481,562 B2 · Method and arrangement for automatic tuning of a controller

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- Number: US 10,481,562 B2
- Document ID: US10481562B2
- Status: Granted
- Kind: B2
- Application number: 15/555,992
- Filed: 2016-03-15
- Published: 2018-03-01
- Granted: 2019-11-19
- Earliest claimed: 2015-03-23
- Assignees: Siemens Aktiengesellschaft
- Applicants: Siemens Aktiengesellschaft
- Inventors: Esmaeil Jahanshahi; John Bradford Schofield; Selvanathan Sivalingam
- Web page: https://patentgrep.com/patent/US10481562B2

## CPC

- G05B 13/024: {in which a parameter or coefficient is automatically adjusted to optimise the performance}
- G05B 11/42: for obtaining a characteristic which is both proportional and time-dependent, e.g. P. I., P. I. D.
- G05B 13/025: {using a perturbation signal}
- G05B 19/0426: {Programming the control sequence}
- G05B 19/42: Recording and playback systems, i.e. in which the program is recorded from a cycle of operations, e.g. the cycle of operations being manually controlled, after which this record is played back on the same machine
- G05B 23/02: Electric testing or monitoring
- G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G)

## Abstract

A method is described for acquiring data for relay-based controller tuning of a controller controlling a system. The method includes determining, based on controller output constraint, a relay amplitude representing an amplitude of a relay signal to be added to steady state controller output to obtain a sum signal to be fed to the system as system input during the acquiring data for relay-based controller tuning; and starting acquiring controller output data and system output data when detecting a steady state of system output while controller output is fed to the system as system input.

## Claims

### Claim 1

A method of determining a relay parameter usable during acquiring of data for relay-based controller tuning of a controller, usable to control a system, comprising:
starting acquiring of controller output data and system output data in response to detecting a steady state of system output while controller output is fed to the system as system input; and
determining, based on controller output constraint and on the controller output data acquired and the system output data acquired, a relay parameter representing an amplitude of a relay signal to be added to steady state controller output to obtain a sum signal to be fed to the system as the system input during the acquiring of the data for relay-based controller tuning,
wherein a first step relay amplitude (RAMP1) is set as follows:
RAMP1=f1*ABS(Y_WIN),
wherein f1 is between 0.08 and 0.12, Y_WIN is a controller output averaged over a moving window having a fixed width, and the relay parameter representing an amplitude of the relay signal is based on the first step relay amplitude (RAMP1),
wherein a second step relay amplitude (RAMP2) is set as follows:
RAMP2=MAX(RAMP1,ABS(f2*X_MU*G−1)),
wherein X is a system output, X_MU is a system output averaged over increasing number of samples, G−1 is an inverse of a gain of the controller, f2 is between 0.08 and 0.12, and the relay parameter representing an amplitude of the relay signal is based on the second step relay amplitude (RAMP2).

### Claim 2 (depends on 1)

The method of claim 1, wherein the determining of the relay parameter is further based on a relay hysteresis (HYS), as given by:
HYS=f4*X_STD
wherein
f4 is between 4 and 6,
X_STD=sqrt (Var_X),
Var_X is a recursive mean of VX or low pass filtered mean of VX,
VX=Sqr (X−X_WIN), and
X_WIN is windowed mean of system output (X).

### Claim 3 (depends on 2)

The method of claim 2, wherein, the relay signal switches from low to high or from high to low in response to ABS(X−XR) being larger than the relay hysteresis (HYS), wherein XR is a system output reference value.

### Claim 4 (depends on 1)

The method of claim 1, wherein the controller output constraint comprises an upper limit controller output (PHOUT) and a lower limit controller output (PLOUT), wherein a third step relay amplitude (RAMP3) is set as follows:
RAMP3=MAX(RAMP2,PRAMP_MIN),
wherein
PRAMP_MIN=5*HYS*MAX(G−1,ABS(Y MAX)/ABS(X_MU)),
HYS is relay hysteresis,
Y MAX=f3*MIN(Yss−PLOUT,PHOUT−Yss),
f3 is between 0.85 and 0.95,
Yss is a steady state controller output, and
wherein the relay parameter representing an amplitude of the relay is based on the third step relay amplitude (RAMP3).

### Claim 5 (depends on 4)

The method of claim 4, wherein the relay parameter representing an amplitude of the relay (RAMP) is obtained according to:
RAMP=MIN(RAMP3,ABS(Y MAX)).

### Claim 6 (depends on 1)

The method of claim 1, wherein
steady state of system output is detected,
if X_WIN is between X_UL and X_LL, setting Index=1,
wherein
X_UL=X_MU+0.5*X_STD, and
X_LL=X_MU−0.5*X_STD,
wherein X is a system output or process output, X_UL is a threshold upper limit and X_LL is a threshold lower limit and X_WIN is a windowed mean of X.

### Claim 7 (depends on 6)

The method of claim 6, further comprising:
detecting a steady-state offset comprising performing:
If ABS(X_WIN-XR) is greater than 2*X_STD,
then setting BOFS=1,
else setting BOFS=0,
wherein
XR is a system output reference value,
BOFS is an offset flag and
X_STD=sqrt (Var_X), Var_X being a recursive mean of VX or low pass filtered mean of VX.

### Claim 8 (depends on 7)

The method of claim 7, further comprising:
setting a new system output reference value (SETPOINT) by performing:
If (Index=1 and BOFS=1),
then set SetPoint=X_MU;
else set SetPoint=XR.

### Claim 9 (depends on 1)

The method of claim 1, further comprising:
determining an inverse gain (G−1) of the controller by:
estimating windowed maximum of controller output, Y_MAX
estimating windowed minimum of controller output, Y_MIN
estimating windowed maximum of process output, X_MAX
estimating windowed minimum of process output, X_MIN
setting INVGtemp=(Y_MAX-Y_MIN)/(X_MAX-X_MIN); and
setting G−1=Recursive mean of INVGtemp.

### Claim 10 (depends on 1)

The method of claim 1, wherein, for performing relay-based controller tuning, controller output data and system output data are acquired, while the sum signal is fed to the system as system input data using relay amplitude as determined previously.

### Claim 11 (depends on 1)

The method of claim 1, wherein, for performing relay-based controller tuning, controller output data and system output data are acquired over several cycles of the relay signal switching from low to high or from high to low.

### Claim 12 (depends on 1)

The method of claim 1, wherein the acquiring of the controller output data and the system output data is stopped, in response to several cycles being performed a maximum number of times or if the controller output is outside a range bounded by PLOUT, PHOUT, wherein PLOUT is lower limit controller output and PHOUT is an upper limit controller output.

### Claim 13 (depends on 1)

The method of claim 1, wherein f1 is 0.1.

### Claim 14 (depends on 2)

The method of claim 2, wherein f4 is 5.

### Claim 15

An arrangement for determining a relay parameter usable during acquiring of data for relay-based controller tuning of a controller to control a system, comprising:
a processor configured to
start acquiring of controller output data and system output data in response to detecting a steady state of system output while controller output is fed to the system as system input; and
determine, based on controller output constraint and on the controller output data acquired and the system output data acquired, a relay parameter representing an amplitude of a relay signal to be added to steady state controller output to obtain a sum signal to be fed to the system as the system input during the acquiring of the data for relay-based controller tuning,
wherein a first step relay amplitude (RAMP1) is set as follows:
RAMP1=f1*ABS(Y_WIN),
wherein f1 is between 0.08 and 0.12, Y_WIN is a controller output averaged over a moving window having a fixed width, and the relay parameter representing an amplitude of the relay signal is based on the first step relay amplitude (RAMP1),
wherein a second step relay amplitude (RAMP2) is set as follows:
RAMP2=MAX(RAMP1,ABS(f2*X_MU*G−1)),
wherein X is a system output, X_MU is a system output averaged over increasing number of samples, G−1 is an inverse of a gain of the controller, f2 is between 0.08 and 0.12, and the relay parameter representing an amplitude of the relay signal is based on the second step relay amplitude (RAMP2).