MATLAB: How to compute control system’s performance parameters

controlControl System Toolboxcontrol systenelectric_motor_controlplotplottingstructurestheory

Hello everyone. 
J = 0.2;
b = 0.1;
K = 0.2;
R = 10;
L = 5;
s = tf('s');
p = K/((J*s+b)*(L*s+R)+K^2);
step(p,200)
[y,t]=step(p,200);
stepinfo(y)
With the following code, I want to measure the rise time. Using the stepinfo command, this is what pops in my command window :
ans = 
  struct with fields:
        RiseTime: 94.5571 %%Rise time
    SettlingTime: 172.5924
     SettlingMin: 0.1735
     SettlingMax: 0.1923
       Overshoot: 0
      Undershoot: 0
            Peak: 0.1923
        PeakTime: 1378
But when I check the parameters using the step response graph, the answer is different.
So, why am I getting two different rise times? Any solution?
Thanks in advance!

Best Answer

You are not calling stepinfo correctlly. 
stepinfo(p)
produces: 
ans = 
  struct with fields:
        RiseTime: 4.4144
    SettlingTime: 8.0108
     SettlingMin: 0.1735
     SettlingMax: 0.1923
       Overshoot: 0
      Undershoot: 0
            Peak: 0.1923
        PeakTime: 23.2961
.
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