Re: Planar Hexapod Kinematics

[Adriaan Pelzer <adriaan-at-trispen.com>]

Hi group and Till,

I'm helping Lukas with the software side of the planar hexapod - we used
trivkins initially to implement our transforms (cartesian to hexapod), but ran
into a few troubles along the way. I just need to clear up a few things for
myself:

On 26-Mar-01 Till Franitza wrote:
> Hi!
> What I experienced with my Clavel-style kinematic is that I couldnt afford
> the kinematics functions being called as often as in the case of trivkins.
> For The genhexkins there was implementd a NO_FORWARD_TRAFO or something that

Are the genhexkins functions called less often than the Trivkins? Sorry, my
knowledge doesn't go that far (yet!). Where do you set NO_FORWARD_TRAFO (.run
file or Makefile?), or is it set already?

> prevents emcmot do calculate the actual TCP-Position out of the Motor
> Positions in each cycle. I dont remember exactly. You should have a look at
> that. Instead I think it is sufficient to assume the actual position is the
> same as the commanded position. So in emcmot this is simply assigned. As far
> as I understood it, emcmot made the control part in cartesian world
> coordinates. In their simple case these were the same as the drive


> coordinates. In the case of Parallelkinematics it is very demanding to make
> the control (PID) in world coordinates and transform back into drive
> coordinates. Many people would like to do that, because it would result in
> better behaviour, but it is simply too time consuming if the forward trafo
> is iterative. In your case, it isnt iterative, but still, methinks, in
> emcmot there are some trafo things that can simply be omitted in order to
> speed things up. Maybe your following errors have something to do with it.

Are all of the above accomplished by setting NO_FORWARD_TRAFO, or is it still
on the to do list?

 
> Lukas du Plessis wrote:
> 
>> Hi everybody
>>
>> We are experiencing problems with implementing the kinematics of our
>> planar hexapod.  When using only the inverse kinematics, by passing
>> EMCMOT_NO_FORWARD_KINEMATICS=1 to insmod when insmoding emcfreqmot.o, we
>> encounter following- errors.  Our .ini file is set up as suggested by
>> Ray to enforce 200 steps per mm (see below)
>>

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E-Mail: Adriaan Pelzer <adriaan-at-trispen.com>
Date: 28-Mar-01
Time: 08:00:10

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