Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Looking for help with this formula

  1. Aug 19, 2008 #1
    The torque equation of joint in 2 link manipulator is given by:
    T= J (dω /dt)+J˚ (dω2/dt)+Cω2 ω +Dω22 +T
    i couldn't find how to write 2 as super script an subscript online any way what i don't know is what C&D stand for in here .can u pls help me?
  2. jcsd
  3. Aug 20, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi mitra1343! Welcome to PF! :smile:
    To write 2, either:

    i] hit the X2 tag above the reply box, or

    ii] type [noparse]2[/noparse] :smile:

    Sorry … what's ω2 ω? and ω22? and why is T on both sides?

    Can you type it out again, and tell us the context also? :smile:
  4. Aug 20, 2008 #3


    User Avatar
    Science Advisor

    If you can point us to where the equation comes from that would be a big help. My guess off the top of my head is that C and D are length dimensions.
  5. Aug 20, 2008 #4
    hi how are u and thanks so much for ur reply
    the formula is about a 2 link planar manipulator .assume that joint l is directly driven by a dc servomotor.(because i don't know how to write power and subscript in messages the formula looks strange that is those numbers in there )any way the formula is T= J (dω /dt)+J˚ (dω2/dt)+Cω2 ω +Dω22 +Tg
    Where J is the combined moment of inertia of motor and manipulator
    J˚ Is the coupling inertia between the 2 joints Cω2 ω is caused by coriolis force; Dω 2 2 is contributed by the centripetal force due to the velocity in the other joint; and Tg is the toeque due to gravity.
    but i can't underestand what C and D stand for will u pls help me ?the formula is from the book robotics for engineers by yoram koren thanks so much again
  6. Aug 21, 2008 #5


    User Avatar
    Science Advisor
    Homework Helper

    Hi mitra1343! :smile:
    (you need to "close" every sub or sup with a [/sub] or [/sup] :wink:)

    (or just use the X2 or X2 tags just above the Reply box)

    I'm still not entirely getting this formula …

    do you mean T= J(dω/dt) + J˚(dω2/dt) + Cω2ω + Dω22 +Tg ?

    From the PF https://www.physicsforums.com/library.php?do=view_item&itemid=86":

    Coriolis force is minus mass times twice the cross-product of angular momentum, and the velocity of the object:

    [tex]-2m\,\mathbf{\omega} \times \mathbf{v}[/tex]

    Centrifugal force depends on position rather than velocity:
    [tex]m\,\mathbf{\omega} \times (\mathbf{\omega} \times \mathbf{r})\,=\,m\,\mathbf{\omega} \times \mathbf{v}[/tex].
    Last edited by a moderator: Apr 23, 2017
  7. Aug 21, 2008 #6
    thank u very much ,yes i meant the same formula u have written ,what exactly D stands for , i'm just an interested beginner with little background of physics thanks again for ur kind reply
    Last edited by a moderator: Apr 23, 2017
  8. Aug 22, 2008 #7


    User Avatar
    Science Advisor

    I would have to see the equiation in the reference. I am only taking guesses.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook