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Question DIY linear actuator vs gear motor control

Discussion in 'DIY Motion Simulator Building Q&A / FAQ' started by chadat23, Apr 30, 2021.

  1. chadat23

    chadat23 New Member

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    Gear motor control makes sense to me; you typically use a potentiometer to always know it's absolute position. How does it work with typical diy linear actuators? I've seen mention of limit switches and pots that can continuously rotate. As a general rule, can the various motor controllers, such as SMC3 and an arduino, work with either sets on inputs or does it get noticeably more complicated dealing with controlling linear actuators?
  2. Ads Master

    Ads Master

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  3. Gadget999

    Gadget999 Well-Known Member

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    My Motion Simulator:
    2DOF, DC motor, Arduino, 6DOF
    I have looked long and hard at the difference between linear actuators and gear motors

    there are advantages and disadvantages for both

    Linear Actuators
    long actuation distances possible
    higher relative cost per performance
    suitable for flight sims
    noisy when ball screws are used

    GearMotors
    shorter actuation distances
    very fast acceleraton and speed possible
    low cost vs performance
    suitable for driving sims
    can be almost silent in operation

    most gearmotor actuators use a potentiometer on the output so any backlash in the motor movement is exaggerated - I have recently designed a gearmotor that has an encoder that is directly on the motor. there is no backlash and the motors are completely stable at rest - you can not even tell they are turned on

    Linear actuators are a much neater nicer solution but they are complicated and work out quite expensive, definitely worth the effort for a flight sim imo

    typically a linear actuator will need an encoder and limit switches for operation
  4. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    My Motion Simulator:
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    If you are referring using DC motors on Linear actuators, controlled via speed control, then yes, you would need encoder or potentiometer for closed loop position control.

    Using Servomotors, you don't need anything, not even limit switches (calibration against hard stop)...
    • Agree Agree x 1
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  5. chadat23

    chadat23 New Member

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    Thanks for all the info. It crossed my mind to use something like the below motor, a 1605 ball screw (or maybe 1204 to better fit inside the conduit and get some more force), abs drain pip, some hardware, steel conduit, 3d printed parts to hold axial alignment, and a u-joint on either end (as apposed to rod ends) to hold rotational alignment. I haven't flushed the idea out yet but at first glance it looks plausible to make it for less than a pgsaw gear motor and they have about the same power so I'd "just" have to get enough mechanical advantage. But, if controlling it is a huge pain in the butt then I'd rather use the gear motor. All that said, having never actually used a motion sim, maybe I'd just be complicating things for nothing.

    https://www.ebay.com/itm/124460382751
  6. Thanos

    Thanos Building the Future one AC Servo at a time... or 6

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    My Motion Simulator:
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    There is always this "open" linear actuator project that has lots of useful information to have a look as well:

    https://opensfx.com/