This question determine the static error constants, 𝐾𝑝, 𝐾𝑣, and 𝐾𝑎 of all the open-loop systems below and then determine the system types. But i keep getting an error.

and below is the MATLAB i wrote.

a = [1,12];                                             
b = [1,15,54];                                          
rt = tf(a,b);                                          

syms s;                                                 % Symbolic variable
num = a;
den = poly2sym(b,s);
gs = num/den;                                           % Symbolic representation of OLTF

Kp = lim(gs);                                           % Position constant, Kp
Kv = lim(s*gs);                                         % Velocity constant, Kv
Ka = lim(s^2*gs);                                       % Acceleration constant, Ka
fprintf('\nc) Determine the static error constants:\n\t\t Kp = %.3f,\n\t\t Kv = %.3f,\n\t\t Ka = %.3f\n', Kp, Kv, Ka)

checkSystemType(Kp,Kv,Ka);
disp (' ')                                              % New line


%% User-defined functions
function y = lim(f)
syms s;
y = limit(f,s,0);
if isnan(y)
    y = inf;
end
end

function checkSystemType(Kp,Kv,Ka)
if ~isinf(Kp) && Kv == 0 && Ka == 0
    disp('System type: 0');
elseif isinf(Kp) && ~isinf(Kv) && Ka == 0
    disp('System type: 1');
elseif isinf(Kp) && isinf(Kv) && ~isinf(Ka)
    disp('System type: 2');
end
end

[Sachini Perera]

thank you soo much for your valuble feedback

Answer 1

[Walter Roberson]

You missed that a represents a polynomial.

a = [1,12];                                             
b = [1,15,54];                                          
rt = tf(a,b);                                          

syms s;                                                 % Symbolic variable
num = poly2sym(a, s)

num = 

den = poly2sym(b,s)

den = 

gs = num/den                                          % Symbolic representation of OLTF

gs = 

Kp = lim(gs)                                           % Position constant, Kp

Kp = 

Kv = lim(s*gs)                                         % Velocity constant, Kv

Kv = 

0

Ka = lim(s^2*gs)                                       % Acceleration constant, Ka

Ka = 

0

fprintf('\nc) Determine the static error constants:\n\t\t Kp = %.3f,\n\t\t Kv = %.3f,\n\t\t Ka = %.3f\n', Kp, Kv, Ka)

c) Determine the static error constants:
		 Kp = 0.222,
		 Kv = 0.000,
		 Ka = 0.000

checkSystemType(Kp,Kv,Ka);

System type: 0

disp (' ')                                              % New line

%% User-defined functions
function y = lim(f)
syms s;
y = limit(f,s,0);
if isnan(y)
    y = inf;
end
end

function checkSystemType(Kp,Kv,Ka)
if ~isinf(Kp) && Kv == 0 && Ka == 0
    disp('System type: 0');
elseif isinf(Kp) && ~isinf(Kv) && Ka == 0
    disp('System type: 1');
elseif isinf(Kp) && isinf(Kv) && ~isinf(Ka)
    disp('System type: 2');
end
end