Rotate Base instead of Robot World?

Kevin

In RS 3.1 I set up a station with an IRB140 in the default position and orientation, carrying wobjRobot and Part1, with fixed Tool1.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

On executing move along Path1, Part1 was moved vertically past Tool1.

 

I used the following procedure to rotate the robot world 20 degrees about Y:

1.  Shut down the controller.

2.  Deleted the reference to wobjRobot from the robot wrist node.

3.  Modify / Position Robot World Y orientation set to 20.

4.  Dragged wobjRobot onto the robot in the object browser, answered No then Yes.

5.  Rotated the toolframe for Tool1 -20 degrees, back to its original position.

6.  Started the controller and synchronised Path1.

 

See the resulting station below.

 

Jump to Target works ok and Move Along Path moves Part1 vertically past the tool as before.

 

When jogging linear Z in the world coordinate system however, the motion is at 20 degrees instead of vertical.

By changing the orientation in Setup Controller / Robot / Base Frame Position, I can correct the jog orientation, but this causes Move Along Path and Jump to Target to be misaligned.

 

Is there a way of rotating the robot Base coordinate system instead of the World, so that both programmed motion and jogging are correctly aligned?

 

Thanks,

 

Kevin

 

TestRotate.zip

Per Svensson

Hi Kevin

The Mechanism Status Window doesn't handle jogging correctly if you have moved the robot by using position robot world. It only works correctly if you have the robot in the default position. What may help you is to choose Base in the Mech Status Window before you start to jogg.

We are aware of this problem. 

Kevin

Hi Per,

The problem occurs when I jog using the virtual Teach Pendant.

Would you please clarify whether or not I will have the same problem when jogging the real robot.

Thanks,

Kevin

Per Svensson

Hi Kevin

The behaviour will be the same in the real controller because the world coordinate system and the baseframe will be in the same position/orientation so if you jogg in world coordinate system it will move vertical to the orientation of the world. So if you want to jogg vertical you should jogg in the workobject coordinate system instead.

Kevin

The following method of rotating the robot base frame appears to result in everything working as expected:

With VC & TP running in Auto mode, motors on.
In the object browser rotate the robot using Modify / Rotate (instead of Position Robot World).
Go to Setup Controller / Robot.
Deselect 'Use controller definition' and enter the required  orientation values.
Click on 'OK'. The controller will restart, applying the new orientation to the base coordinate frame.
'Move along path' works ok  for paths defined using both stationary and carried tools.
Jogging via the Mech Status window or TP works correctly for World, Base, Tool and Wobj coordinate systems.
Regards,
Kevin

Per Svensson

Hi Kevin

You are right BUT be aware of that you have actually changed the baseframe position relative world in the robot so if you are going to download this to a real controller you also need to modify the baseframe in the real controller, and normally in a single robot solution you don't do that.

If you want to test what's going to happen you can take these steps

1. Move the robot and change the baseframe (as you did previous)
2. Create a path with a couple of targets.
3. Sync the path to the virtual controller.
4. Change back the position of the robot to zero and also the baseframe.
5. Sync the path from VC up to RS.
You will now be able to see that the path is still in the old position and motion will be totally diffrent if you even can reach the targets. 

Kevin

Hi Per,

Thanks for explaining that.

I suppose it is pretty unusual to want to mount the robot at a strange angle. The reason is that the fixed tool will not work correctly unless it is horizontal, and in the real application there is an approach to singularity with the robot mounted normally. Rotating the base 20 degrees about Y ensures that axes 4 and 6 remain far from coaxial.

I feel it will be confusing to have the World coordinate system rotated since only the robot is physically rotated, the rest of the cell having the usual orientation. I presume that if I backup from the VC and restore to the real robot the baseframe will be automatically rotated to match the station.

Regards,

Kevin