Soemething a little different

Hi everyone,

My colleague at university requires an interesting axis combination whereby 1 axis is coupled to another but also free to move. This is like placing one linear axis on another (parallel to each other) and then having the 2nd axis follow the first but also able to move independent of the first. He cannot simply mount one axis on top of the other so I said i would take a look at whether this can be easily implemented in Linuxcnc. Ive never looked at the gantry kins but was thinking there might be some clues in there. My initial thought is the kinematics would be modified so
joint 1 = a + joint 0 i.e axis 2 follows axis 1 and moves additionally by some amount a. Do you think this can be done?

Thanks
Anthony

[quote="An" post=14955My initial thought is the kinematics would be modified so
joint 1 = a + joint 0 i.e axis 2 follows axis 1 and moves additionally by some amount a. Do you think this can be done?[/quote]

Yes, that can be done, but will it do what is required?

Perhaps start at the other end. How would you anticipate controlling the machine with G-code? What axis letters would you expect to use, and what would be the effect at the actuators?

Thanks for the Reply Andy. Hmm all good points and i need to find out more from him. In the meantime do you think it can all be done in the kinematics file, i think I can manage this, otherwise probably too hard basket.

Thanks
Anthony

An wrote: Thanks for the Reply Andy. Hmm all good points and i need to find out more from him. In the meantime do you think it can all be done in the kinematics file, i think I can manage this, otherwise probably too hard basket.

Depending on what is required, I think it should be doable in kins. And quite possibly in HAL.

Ok, thanks Andy. I just found the below reply of yours to another user from a couple of years back and im wondering what the rational for doing this type of compensation in HAL over kins is?

Thanks

forum.linuxcnc.org/10-advanced-configura...ensation-with-2-7-11

What is the advantage of doing these compensations in Hal over kinematics? More accurate

It would look a bit like this:
component wobbly_table;
pin in float x-in;
pin in float y-in;
pin in float z-in;
pin out float z-out;
function _;
;;

FUNCTION(_){
zout = z_in + 0.1 * x_in + 0.2 * y_in + 0.01 * x_in * y_in;
}

linuxcnc.org/docs/2.7/html/hal/comp.html

An wrote: Ok, thanks Andy. I just found the below reply of yours to another user from a couple of years back and im wondering what the rational for doing this type of compensation in HAL over kins is?l

That discussion was about a tiny correction. That can be done in kins (there is an example kins that trued-up an out-of-square machine)
wiki.linuxcnc.org/uploads/millkins.c

I am still very unclear what this machine looks like, so it's very hard to decide how best to control it.