Robot World Frame

$ROBROOT should always be held in place. $WORLD can be shifted if required. Especially if robot is mounted upside down or similar. Relationship is always $ROBROOT -> $WORLD -> Base..

I see no reason to ever fiddle with robroot.

Actually the World Coordinate System is fixed by $WORLD = $NULLFRAME (both frames are write protected).

$ROBROOT defines the frame going from Word Coordinate System to the Robot Coordinate System.

Therefore the correct relationship would be

Robot Coordinate System <== World Coordinate System ==> Base Coordinate System

I do not know too much about KUKA.Sim, but I would guess by just changing the Z-Value from $ROBROOT would be a flying robot. Maybe you would need to set the robot on top of a platform

correct...

just created new program, added P1 as motion with tool 0, base 0 (world) and touched it up when robot was at home.

then run program and it just zips through since all points are same...

then modified $ROBROOT by adding 900mm to Z (just for fun). the nice thing is one can do this change without reboot:

then i run the same program again. this time P1 is not the same as home since P1 is tied to world that is sunk by 900mm.

home position is the "cannon" since axis specific, but the added motion to P1 moved robot down, as if robot was on 900mm pedestal

of course since you never select any base.

your P1 motion refers to WORLD.

try changing that to Base 1 for example and see how your program runs when Base 1 is changed to a different value.

for example, test with values such as:

{X 0, Y 0, Z 0, A 0, B 0, C 0} ; default (this is what you see now)

{X 0, Y 0, Z 200, A 0, B 0, C 0} ; base lifted up by 200mm

{X 300, Y 0, Z 0, A 0, B 0, C 0} ; base moved away by 300mm

{X 0, Y 0, Z 0, A 20, B 0, C 0} ; base rotated about Z axis

{X 0, Y 0, Z 0, A 0, B 10, C 0} ; base rotated about Y axis

and not sure why you are trying to manipulate $ROBROOT. this should never change in program. the only time this is assigned value is when kinematics is mounted "elsewhere" (robot arm mounted on wall, or ceiling or on KL rail...)

Quote from panic mode

and not sure why you are trying to manipulate $ROBROOT. this should never change in program. the only time this is assigned value is when kinematics is mounted "elsewhere" (robot arm mounted on wall, or ceiling or on KL rail...)

Thanks as always.... I was trying to understand what $ROBROOT does so I was just playing around in KUKA.SIM but yes as per what you said I cant change $ROBROOT like that. For changing robroot I had to change it using "Move Robot World Frame". We are doing that because at times we have our robot mounted on a 15 degree plane, and when we use WORLDFRAME to job in Z it jogs in 15 degree angle rather than up and down because of how its mounted so we were seeing how we could change this so that worldframe z is always perpendicular to the ground

Did some testing with this yesterday on a physical KR10 R1100-2 HO robot and Jaiiyer was on the phone testing it in Kuka Sim. Just wanted to share some results.

1. On the physical robot the easiest way we found to update "how the robot is positioned" is in WorkVisual under Machine data configuration there is a Cell parameters > Root point that sets the XYZ position, ABC rotation and how the base is mounted Floor Wall Ceiling.

2. In Root point we offset the Z up 500mm and tipped it at an angle to of B:22deg to represent a project we are working on.

3. After deploying this change, we got a safety configuration activation code error and a safety stop. To clear this we did a cold start (reload files), and then go into the pendant under Configuration> Safety Configuration and accepted the safety configuration change

4. At this point the robot targets previously touched up were lower (as Panic Mode demonstrated earlier) and rotated from the base rotation.

We went and looked at $ROBROOT and it has the same offsets that we set in the Cell parameters >Root point. We also checked $WORLD and it was all zeros as expected.

Previously we tried putting values directly in $ROBROOT.Z from the pendant Variable > Single and it acted as though it was write protected. and gave the information/warning Z variable write -protected (Taskname: KFI). My guess is it has to recompile the motion planner when changing the base position of the robot and this requires a cold start.


jaiiyer feel free to add to this, or correct me.
In KukaSim we tried to overwrite the $ROBROOT as Jai showed in a previous post and it was wiped out each time we started the program.

We got it to work by clicking on the MoveWorldframe button at the top of the main page, and we were able to move the worldframe down -500mm.

When we ran the program and the points appeared to be lower, $World was at all zeros and $ROBROOT was at Z+500.


Two quick takeaways on this topic:

Why you’d want to do this:
We’re doing this on a current project because our robot base is elevated and tilted at 22° to improve reach.

1. Setting the robot base to match these parameters allows for intuitive jogging in World Coordinates—for example, +Z aligns with the physical floor.

2. Physical floor is zero so that everything in the cell is in the +Z space.

3. If your robot base is tilted or rotated in a way that doesn’t match the rest of your physical cell, adjusting the base settings lets your World Coordinates align with your actual workspace. This is especially helpful when setting up multiple base frames, as their positions will use intuitive, straightforward values instead of being skewed by the robot base’s orientation.

I am of course open to correction and questions.

Quote from funnyguyjake

Previously we tried putting values directly in $ROBROOT.Z from the pendant Variable > Single and it acted as though it was write protected.

It is write-protected. $ROBROOT is always the bottom center of the robot arm.

For a robot with no unusual kinematics, $WORLD and $ROBROOT are always the same by default. A wall-mounted robot should have a 90deg difference between them, and a ceiling-mount robot should have a 180deg difference. But this is part of the robot setup, not something changed programatically. In $WORLD, Z+ should always be antiparallel to gravity, as this is part of how the robot calculates the effects of $LOAD.

For a robot with certain kinds of external kinematics (say, robot mounted on an external axis), $ROBROOT moves with the base of the robot, while $WORLD is located where $ROBROOT is when the external axis is at 0.

$BASE is always an offset from $WORLD.