hey. I keep getting an error for this code. If anyone could help me it would be greatly appreciated.

Question

Sachini Perera 2021-10-6

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1468171-hey-i-keep-getting-an-error-for-this-code-if-anyone-could-help-me-it-would-be-greatly-appreciated

回答： Paul 2021-10-6

采纳的回答： C B

clear;

clc;

a = [1,12];

b = [1,15,54];

rt = tf(a,b);

% b) Determine the steady state errors for the open-loop systems below with the following inputs: 8𝑢(𝑡), 8𝑡𝑢(𝑡), and 8𝑡2𝑢(𝑡).

syms s;

num = a;

den = poly2sym(b,s);

gs = num/den;

es = 8/(1+lim(gs)); % Steady-state error with step input

er = 8/(lim(s*gs)); % Steady-state error with ramp input

ep = 8/(lim(s^2*gs)); % Steady-state error with parabola input

fprintf('b) Determine the steady state errors:\n\t\t with step input = %.3f,\n\t\t with ramp input = %.3f,\n\t\t with parabola input = %.3f\n', es, er, ep)

%% User-defined functions

function y = lim(f)

syms s;

y = limit(f,s,0);

if isnan(y)

y = inf;

end

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Answer 1

C B 2021-10-6

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1468171-hey-i-keep-getting-an-error-for-this-code-if-anyone-could-help-me-it-would-be-greatly-appreciated#answer_802846

编辑：C B 2021-10-6

在 MATLAB Online 中打开

It was because value of (1+lim(gs)) was

a=(1+lim(gs))
 
a =
 
[55/54, 11/9]

clear;
clc;
a = [1,12];                                           
b = [1,15,54];                                        
rt = tf(a,b);                                        
% b) Determine the steady state errors for the open-loop systems below with the following inputs: 8𝑢(𝑡), 8𝑡𝑢(𝑡), and 8𝑡2𝑢(𝑡).
syms s;                                               
num = a;
den = poly2sym(b,s);
gs = num/den;                                        
es = 8./(1+lim(gs));                                     % Steady-state error with step input
er = 8./(lim(s*gs));                                     % Steady-state error with ramp input
ep = 8./(lim(s^2*gs));                                   % Steady-state error with parabola input
fprintf('b) Determine the steady state errors:\n\t\t with step input = %.3f,\n\t\t with ramp input = %.3f,\n\t\t with parabola input = %.3f\n', es, er, ep)
%% User-defined functions
function y = lim(f)
syms s;
y = limit(f,s,0);
if isnan(y)
y = inf;
end
end