Control System Analysis Techniques course error

In the Time domain section of the course when I use the step function to plot the grpah it keeps saying i am wrong even though it is the exact same code and graph. Those anyone have anny solutions

below is the code

s = tf('s');
quadcopter_ol = 0.04133/(s + 0.01479);
controller = zpk(-5,0,100);

Task 1

step(quadcopter_ol)

[Walter Roberson]

Is it look for step(controller) ?

s = tf('s');
quadcopter_ol = 0.04133/(s + 0.01479);
controller = zpk(-5,0,100);
step(controller)

[Dunbarin]

No it’s you’re meant to use the step function on the quadcopter, even the solution in the course does the same thing I do and the graphs are the same but it keeps saying I’m wrong

Answer 1

[Sam Chak]

Hi @Dunbarin

If this topic is related to control systems, you are probably required to implement the controller on the open-loop quadcopter to form a closed-loop control system with the desired characteristics, such as the settling time.

s = tf('s');

% Open-loop system
quadcopter_ol = 0.04133/(s + 0.01479)

quadcopter_ol =
 
    0.04133
  -----------
  s + 0.01479
 
Continuous-time transfer function.

% Controller
controller = zpk(-5,0,100)

controller =
 
  100 (s+5)
  ---------
      s
 
Continuous-time zero/pole/gain model.

% Closed-loop system
closedLoop = feedback(controller*quadcopter_ol, 1)

closedLoop =
 
       4.133 (s+5)
  ----------------------
  (s^2 + 4.148s + 20.66)
 
Continuous-time zero/pole/gain model.

% Step response of the closed-loop system
step(closedLoop), grid on

Warning: Graphics acceleration hardware is unavailable. Graphics quality and performance might be diminished. See MATLAB System Requirements.

[Dunbarin]

Thank you for your reply but the task specifically askes you to use the step function on quadcopter_ol, and what you did is the immediate task after completing what I said.

My issue is that I used the step function correctly but it still says I failed

[Sam Chak]

Hi @Dunbarin

I’m sorry to hear that. Have you resolved the issue? If not, please contact technical support for assistance.

[Dunbarin]

No I haven't resolved the issue yet but I have reached to tech support