Why Value of type "tf"is not convertible to double?

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pawel Wisniewski
pawel Wisniewski on 22 Jan 2022
Commented: Cris LaPierre on 23 Jan 2022
clc;
clear all;
x0=[0 0 0 0 0 0 ];
tic
xOptSim=fminsearch(@robot,x0);
car_sys = 500 s + 12500 ----------------------- 200 s^2 + 500 s + 12500 Continuous-time transfer function.
Warning: Ignoring extra legend entries.
Unable to perform assignment because value of type 'tf' is not convertible to 'double'.

Error in fminsearch (line 201)
fv(:,1) = funfcn(x,varargin{:});

Caused by:
Error using double
Conversion to double from tf is not possible.
t2=toc;
function [car_sys,u1] = robot(parametry)
X1=parametry(1);
X2=parametry(2);
X3=parametry(3);
X4=parametry(4);
X5=parametry(5);
X6=parametry(6);
m = 200; %kg
b = 500; %Ns/m
k = 12500; %N/m
car_sys = tf([b k],[m b k])
t = 0:0.001:10;
wd=7;
% Respuesta a bajas frecuencias
figure
u1 = sin(wd/2*t)+cos(wd*t);
lsim(car_sys, u1, t)
title('Niska charakterystyka częstotliwościowa')
legend('Odpowiedź systemu' , 'Lokalizacja' , 'SE')
ylim([-4 4])
end

Answers (1)

Cris LaPierre
Cris LaPierre on 23 Jan 2022
I believe the issue is because the order of your function outputs is not correct. The first output of your function needs to be the solution, u1. Try reversing the order of your output arguments.
x0=[0 0 0 0 0 0 ];
xOptSim=fminsearch(@robot,x0);
car_sys = 500 s + 12500 ----------------------- 200 s^2 + 500 s + 12500 Continuous-time transfer function.
Warning: Ignoring extra legend entries.
Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 1-by-10001.

Error in fminsearch (line 201)
fv(:,1) = funfcn(x,varargin{:});
function [u1,car_sys] = robot(parametry)
X1=parametry(1);
X2=parametry(2);
X3=parametry(3);
X4=parametry(4);
X5=parametry(5);
X6=parametry(6);
m = 200; %kg
b = 500; %Ns/m
k = 12500; %N/m
car_sys = tf([b k],[m b k])
t = 0:0.001:10;
wd=7;
% Respuesta a bajas frecuencias
figure
u1 = sin(wd/2*t)+cos(wd*t);
lsim(car_sys, u1, t)
title('Niska charakterystyka częstotliwościowa')
legend('Odpowiedź systemu' , 'Lokalizacja' , 'SE')
ylim([-4 4])
end
  1 Comment
Cris LaPierre
Cris LaPierre on 23 Jan 2022
The new error is because your solution vector, u1, is not the same size as x0. One thing to look into is why you are not using your X values in your function.

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