How to perform a move with a force limit?

My UR10 removes coils from a bobbin. Friction between coil and bobbin is an issue so simply using MoveL with any speed/acceleration parameter results in a protective stop.

I currently run this: (pseudocode)
Loop 10 times:
- 5mm relative move on tool X-axis
- Wait force()<100

The above performs reasonably well, but as it comes to a stop nine times, the robot must also overcome the resting friction of the coil each time, so it takes ages. Since sliding friction is always less (yay physics), it would be better to get run the movement in one go.

I tried using the Force function in the Polyscope, but it doesn't really do what I want it to do, which is to move along tool axis with a limited force. If I set it to 100N on X-axis and give a relative 50mm movement command, the robot never reaches the end point of the movement but instead tries for a random amount of time and then skips to the next step in the program which causes it to try to move through the winding machine's frame. Why doesn't the robot finish the movement?

Use an if statement and check the box for checking the condition continuously. The condition you are looking for is the force to below a certain threshold, 100 N for instance. 

Under the if statement you place the full move followed by a flag to let you know the full motion was completed.  If the If statement exits before the full point was reached the flag will not turn true 

Then in the else else you will place a stopj(12) command, this will bring the robot to a clean stop quickly following any breaking of the if statement. 

You can then then wrap this whole statement in a loop that executed so long as the made it flag is false. Something like this pseudo code

var madeIt=False
Loop (not madeIt)
  if ( force()<100) # make sure check box is checked makes it a while loop
    MoveL
      OffTheBobbinPoint
      madeIt=True
  else
    stopj(12)
  end if
end Loop

Hello

The pseudo above won't work in my case, because I am commanding a MoveL variable p[0.05,0.0,0.0,0.0,0.0,0.0]. Thus every time the force reading goes over the value set in the if statement, the StopL command is ran and whenever the robot settles and force falls below threshold, the MoveL is ran once again, effectively starting the 50mm move from zero once again. So what happens is the robot goes for a few millimeters, then stops. Moves a bit, stops, moves a bit, stops, until it is clear of the bobbin. Then runs the full 50mm because it can move unobstructed below the force threshold and only after that exits the Loop. This is slightly bad because the last full 50mm move causes it to crash to the other half of the bobbin :smiley:

I didn't know variables could be used inside a Move command like the way you use madeIt. That's a good idea!

The reason I don't use a real waypoint here is because this function goes inside a Destack function and the coils that are picked vary in width from 120mm to 250mm. Using a waypoint would mean that basically only one of the coil types would move fine and the other types would try to cut the corner of the bobbin.

I guess I have to calculate an actual Waypoint to be whatever+X[50mm] instead a variable move AND to use a madeIt type variable to check for actually reaching the Waypoint. Or to exit the loop whenever the tool is inside a "safe box".

Thank you for the ideas!

I solved this one!

Thread 1:
pos = get_actual_tcp_pose() ; creates a vector p[x,y,z,rx,ry,rz]

Thread 2:
While pos[1] < 0.09 ; Second element in vector pos[]
 if force()<150 ; This is continuously checked
  movel(pose_trans(get_forward_kin(),p[0.05,0.0,0.0,0.0,0.0,0.0],a=0.05,v=1)) ; Move along tool X-axis
 elseif         ; If force exceeds threshold
  stopl(0.1) ; soft-ish stop