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direct drive Brushless motors for robotics application.
  • Metabolik
    Hi ,

    I just ran a startup around open source and robots. For my product developpement I need to create a motor block dedicated to robotics.
    Gimbals BLDC motors are pretty close to my needs; indeed, my specific needs is to measure efficiently the motor torque.
    To measure the motor torque I plan to use impedance control (measure torque with input current). I also need to avoid any output mechanical reduction to reduce torque noise and keep the natural motor elasticity.

    During my google researsh I found some good informations on this forum... So I choose to ask you some advice around BLDC motors!

    There is 2 differents possibility for my developpement :
    - use an existing one
    - work with an industrial specialist to create my own

    here is my motors specs :

    max diameter: 32 mm
    max length: 28 mm
    power: 6-10W
    nominal voltage: 24v
    max speed: 2 rps (revolution per second)
    max torque: 3 Nm
    optimal working point 2 N.m @ 0.5 rps

    Do you know any existing motors that can approximately match with it?
    If not, do you know any guys/company who can work with us to develop this kind of device?
  • Garug
    That is pretty much specification for robotic servo. There is reason geared servos are used in many applications, it is high tongue on a small package.

    There is servos with BLDC motors, but direct driven BLDC just can not meet those specifications.

    The tongue is posible, but it takes a bigger motor and more power.
  • Metabolik
    Thank you for your reply Garug,

    Indeed my specification are really challenging, but how to change the world if it's not ;)

    This is my bigger motor (probably not the most challenging), I plan to create some smaller ones, for example :

    size : 36x36x36mm
    nominal voltage: 24v
    Torque > 0.5Nm
    Max torque > 1.5Nm
    Speed >= 2 rps
    No reduction stage

    That sound more realistic for you?

    Why I will need more power if I don't use a big reduction stage? where is the loss? that is because it's difficult (impossible?) to build extra slow BLDC motors ?

    another question, why Gimbals BLDC are particularly adapted to camera stabilization?
  • Garug
    "why Gimbals BLDC are particularly adapted to camera stabilization?" I do not understand what you mean?

    The tongue limits come form strength of magnets and winding resistance. Superconductor motor probably would not have such limitations :)
  • Metabolik
    ""why Gimbals BLDC are particularly adapted to camera stabilization?" I do not understand what you mean? "

    I mean why using this kind of motors for camera stabilization?
  • Garug
    They are perfect for it. Servos usually have at least some free play because of gears, they are also slow to accelerate because of gears and Servo motor inertia. Direct driven brushless motor does not suffer from these problems, also the tongue they provide is enough for gimbals.
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