Error when inputting step function

m2 = 350;
m1 = 10;
Ks = 10000;
Kw = 500000;
b = 1000;
Num = Kw* [b Ks];
Den = m1*m2*[1 (b/m1 + b/m2) (Ks/m1 + Ks/m2 + Kw/m1) b*Kw/ (m1*m2) (Ks*Kw) / (m1*m2)];
step(Num,Den)

Error message:

>> help

Check for incorrect argument data type or missing argument in call to function 'step'.

Error in help (line 8)

step(Num,Den)

Answer 1

[Star Strider]

The code is missing a setp (pun intended) —

m2 = 350;
m1 = 10;
Ks = 10000;
Kw = 500000;
b = 1000;
Num = Kw* [b Ks];
Den = m1*m2*[1 (b/m1 + b/m2) (Ks/m1 + Ks/m2 + Kw/m1) b*Kw/ (m1*m2) (Ks*Kw) / (m1*m2)];
sys = tf(Num,Den)                                                                           % Create A 'system' Object With The 'tf' Function (In This Instance)

sys =
 
                     5e08 s + 5e09
  ----------------------------------------------------
  3500 s^4 + 360000 s^3 + 1.786e08 s^2 + 5e08 s + 5e09
 
Continuous-time transfer function.

figure
stepplot(sys)

.