Roll control with a reaction wheel

Discussion in 'Rocketry Electronics and Software' started by alexzogh, Mar 24, 2020 at 2:36 PM.

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  1. Mar 24, 2020 at 2:36 PM #1

    alexzogh

    alexzogh

    alexzogh

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    I've been working on a set of rollerons for roll control over the last month with limited success. Yesterday, while catching up on the latest bps.space video's, he mentioned and showed using a reaction wheel. Starts the discussion at 5:05




    Has anyone else tried this? I briefly toyed with the idea of a control moment gyroscope, but this seems much cleaner.
     
  2. Mar 24, 2020 at 6:01 PM #2

    QBrandt

    QBrandt

    QBrandt

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    Roll control was the objective of the Midwest High Power Rocketry Competition a few years ago.
    Two launches were required. On the first, the objective was to minimize the rocket's roll between burnout and deployment. On the second, the objective was to direct a fixed camera to cardinal directions by rolling the rocket.

    A lot of teams (including mine) used reaction wheels. Most of the rest used control surfaces. One used a cold gas expansion system that I don't remember much about. (Rollerons were not allowed because they are not an active system.)
    There weren't any complete successes, probably because tuning something like this requires a lot of flights beyond the timeline and budget of college teams.

    If you want to make a system like these, it might be worth reaching out to Gary Stroick (President/Owner of OffWeGo Rocketry, one of the runners of the competition), he probably has all of the teams' reports.
    The basic approach we took was to design a rocket with a ballpark payload mass for the motor/wheel/battery/etc., then determine the roll moment of inertia. From that, an assumed initial roll (1.5 Hz IIRC) and a chosen roll acceleration (be able to turn 90 degrees in 1 second, IIRC) we sized an electric motor and reaction wheel. Then a lot of iteration (Change in mass changes MoI of rocket, changes required MoI of wheel, etc.). After it was built, there was a fair amount of PID tuning and ground testing.
     
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  3. Mar 25, 2020 at 2:00 PM #3

    alexzogh

    alexzogh

    alexzogh

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    Thanks for the note. I've started the hunt for information, although I suspect it might just be easier to build one from scratch.
     

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