Function 'subindex' is not defined for values of class 'ss' of 'zpk'

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Barkat
Barkat 2017-10-26
编辑： Walter Roberson 2017-10-26
Dear All
I am following MATLAB tutorial in Mathworks "Designing PID for Disturbance Rejection with PID Tuner" While following this tutorial, I got the following error in the picture. and another error is
"Function 'subsindex' is not defined for values of class 'zpk'."
The errors occurred after the following commands
G = zpk(-5,[-1 -2 -3 -4],6,'OutputDelay',1);
G.InputName = 'u';
G.OutputName = 'y';
C = pid(0.64362,0.30314);
C.InputName = 'e';
C.OutputName = 'u';
b = 0.7;
% The following code constructs an ISA-PID from F and C
F = tf([b*C.Kp C.Ki],[C.Kp C.Ki]);
F.InputName = 'r';
F.OutputName = 'uf';
Sum = sumblk('e','uf','y','+-');
ISAPID = connect(C,F,Sum,{'r','y'},'u');
tf(ISAPID)
% Closed-loop system with PI controller for reference tracking
sys1 = feedback(G*C,1);
% Closed-loop system with ISA-PID controller
sys2 = connect(ISAPID,G,{'r','u'},'y');
% Compare responses
step(sys1,'r-',sys2(1),'b.');
legend('show','location','southeast')
title('Reference Tracking')
The link of the tutorial is : https://www.mathworks.com/help/control/examples/designing-pid-for-disturbance-rejection-with-pid-tuner.html
Can anyone guide me how to remove these errors ?
Thank you

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采纳的回答

Steven Lord
Steven Lord 2017-10-26
If you run these lines of code one by one, on which line does the error occur?
My suspicion is that you have created a variable named connect if the error occurs on the line of code where you're trying to call the connect function.

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