I am trying to implement PID control loop for flight control of Quanser VTOL(vertical take off and Landing system) in Simulink.

VTOL Information book is placed at link below: https://www.mediafire.com/file/yszb2ytbjv5966k/Info_book.pdf/file

Please check the last pages specifically last two pages.

I have made my model in Simulink 2015 and i also uploaded my model on media fire,link is given below:


I am trying to get graph like the one in attached snap(this graph appears on last page of book). I have also attached snap of control loop(it is shown on pg 22/26 in book). I have also attached of my simulink model. My issue is that my simulink graph response is not matching that in book. I have made my simulink model exactly like the PID control loop shown on pg 22/26 and i have used exactly same values of variables like K, Kt etc but i am not getting proper response, instead i am getting a decaying(damped) response. I have changed the limits of saturation block but still this damping persists

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My MATLAB code for variables/parameters values is:

close all

Update I am attaching a new snap where i have changed limits of saturation block and now its limits are 0 to 4 and now graph shape becomes relatively reasonable. I can not entirely remove this block as it is also included in the snap shown on book enter image description here

  • 1
    \$\begingroup\$ what does happen if you increase the duty cycle of the pulse ? \$\endgroup\$
    – Rahmany
    Nov 7, 2022 at 15:28
  • \$\begingroup\$ Try to use built-in pid block rather than using separate gain blocks for proportional,integral and derivative gains \$\endgroup\$
    – DSP_CS
    Nov 7, 2022 at 16:40
  • \$\begingroup\$ As @Rahmany has said. The Figure 4.6 from the manufacturer indicates that the rise time is nearly 1 second and the input command given appears to be of 1/6 Hz frequency. Try changing the input command to the same frequency and duty cycle. \$\endgroup\$
    – AJN
    Nov 7, 2022 at 17:12
  • \$\begingroup\$ @Rahmany no change in output, if i increase duty cycle of rectangular \$\endgroup\$
    – DSP_CS
    Nov 8, 2022 at 11:30
  • 1
    \$\begingroup\$ what's the step response? can you update your post with its graph? \$\endgroup\$
    – Rahmany
    Nov 8, 2022 at 14:29

1 Answer 1


When i changed the limits of saturation block,damping was no more there.For this purpose i used lower limit value as '0' and upper limit value as '4'.


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