What’s the best way to set up a continuous rotation for an axis?

pgoellner

Hi everyone,

I´m new here and try to set up a new kinematics.
For that reason my axis have to be in a “(continuous-) rotation-mode” which means that all angles must be in 0..360° (-> Angle%360).
From my transformation I got values from between 0° and 360° (or +-180°).
If I will do a move from 0° to 350° the axis should not move +350°, instead the axis should take the “short” path with -10°.

I enable in my kinematics class the function “IsContinuousRotationAxis(){… return = true;}”.
In my opinion this should solve this problem but it don’t.
Did I something wrong, or do I miss a setting?

Thanks in advance, Best Peter

Duet 3 Firmware (RepRapFirmware: v3.01-dev; RRFLibraries: dev; CoreNG: dev; FreeRTOS: master; DuetWiFiSocketServer: master)

Phaedrux

It sounds like some work is being done for this for version 3.2

https://forum.duet3d.com/topic/16788/u-axis-without-limit/12?_=1592935944738

pgoellner

@Phaedrux Thanks for that respone.

bondus

@pgoellner It worked when I played around with it.

When IsContinuousRotationAxis() returns true the firmware should always find the closest direction to rotate to reach the goal.

It has to be a G0 move for it to do this.

arhi

is there a way to set "speed" for continuousRotationAxis (start/stop) or at least multiple of 360 degrees (I need it to turn e.g. 20 turns)

bondus

@arhi It's supposed to be used with polar/arm printers, if you move 360 degrees you end up at the same place.

M92 sets steps/deg in this case and not steps/mm. For example a 0.9deg stepper with 16 microstepping and a 20:1 gearbox will be 16*20/0.9 = 355.556 steps/deg

arhi

@bondus said in What’s the best way to set up a continuous rotation for an axis?:

@arhi It's supposed to be used with polar/arm printers

Yes, but I'm thinking about multi axes cnc and want to turn a thread for e.g.
I can do it as ton of small moves but maybe a single multiturn move?
Or, I'm thinking about 3D scanner where I need to do 5-6 rotations of the table,
or, I'm thinking about "presenter" with rotating base + pan and tilt
or ..

There'a a million reasons one would like to have a precise continuous rotation of one axis

bondus

@arhi If you do not return true from IsContinuousRotationAxis() that is exactly what you get. You can still rotate multiple rotations, it only affects the automatic wrapping.

arhi

ah, perfect, thanks