You are right. It takes 12 numbers to specify the location the orientation of two arms. But in a typical robot there will be more than 12 axis. If you look at the stat of the art, there could be 100+ axis, see below.
With a typical robot the number of axis may not equal the number of degrees used to specify the pose. For example it is common to specify an X,Y,Z and orientation using six numbers but it very well might be there as 7 degrees (or more) of freedom in the arm. It other words there would be an infinite number of inverse kinematic solutions. And a controller would choose a plan to (say) minimize angular velocity, accelerations or toque and to avoid collisions of (say) the elbow hitting nothing while moving the hand. Typically you need extra axis to avoid collisions and "gimbal locks" and such. Machine tools are mostly very simple. We design the tool so all axis are square so to move 1 inch in X we simply move the X motor one inch. But a robot's axis are likely NOT square and the axis do not meet at the origen and the angles between the axis can change. Here is a great video of a toy-like 18 axis machine. But the control software is very primitive and depends on human in the loop remote control for path planning https://youtu.be/aH07qF_bhgA?t=9s MUCH more sophisticated control is used here. The machine is given only a high level goal. "lift and cary the box" and is otherwise self directed (notice the q-codes on the box and doors and laser scanner in the head.) https://youtu.be/rVlhMGQgDkY?t=1m22s <https://youtu.be/rVlhMGQgDkY?t=1m22s> H <https://youtu.be/rVlhMGQgDkY?t=1m22s>ow many axis are running here? Between jack and Sophia, maybe 100+ Jack is the car, sophia is in the passenger seat. This is the current state of the art. (Do NOT over estimate sophia, she uses plenty of "dumb tricks" like responding with "yes, I agree" when she has no clue what you just said) In the end this is motion control. Many dozens of motors are running and being synchronized https://youtu.be/vtX-qVUfCKI?t=40s On Thu, Jun 15, 2017 at 9:52 AM, andy pugh <bodge...@gmail.com> wrote: > On 15 June 2017 at 17:36, Chris Albertson <albertson.ch...@gmail.com> > wrote: > > > It depends on one's approach to a multi arm/leg robot. You can > > treat it as two 6 DOF arms or > > as one 12 DOF assembly. > > > > I can certainly imagine a 2-arm robot using XYZ and UVW to position two > arms. Though then you run out of orientation angles for the UVW tool. > > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is designed > for the especial use of mechanical geniuses, daredevils and lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1916 > ------------------------------------------------------------ > ------------------ > Check out the vibrant tech community on one of the world's most > engaging tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
