Initially I posted this question on EE Stack Exchange but I am also posting it here in Space Stack Exchange so I may get attention from a much related audience.

I am interested in control systems applications and currently I am trying to learn about Quanser rotary inverted pendulum system. I studied that it can be used to model/demonstrate some aspects of rocket system especially during take off (Launch) stage but I am unable to understand its relation to rocket. What are those aspects and how they relate? Can some one please guide?

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    $\begingroup$ Have you found out the equations which describe the motion of the inverted pendulum ? If so, papers similar to this will give the equations for the rocket. You will notice that they both deal with unstable, second order systems. $\endgroup$
    – AJN
    Dec 1, 2021 at 12:09

1 Answer 1


It is tempting to think of a rocket as an inverted pendulum system: both are second order unstable systems, consisting of a long stick with a control mechanism on one end. However, there are crucial differences:

  1. The control input is fundamentally different.
  2. The inverted pendulum has two stationary states: one unstable (the upright position) and one is stable (pendulum hanging down), while for a rocket during launch, there is no equilibrium state (think about what happens if the pointy end of the rocket points down and the flamy end points up...)

If you want to learn about control systems, it is an excellent exercise to derive the equations of motion and control inputs for both systems and analyze the differences!

  • $\begingroup$ If Rocket is similar to inverted pendulum during launch stage then what about return stage when rocket comes back to earth?that stage will also be similar to inverted pendulum? $\endgroup$
    – DSP_CS
    Dec 2, 2021 at 18:20

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