IRB 6700 -- problems recovering from a jog collision

    IRB6700, IRC5, RW 6.12

    I have a set of new IRBs that are being much more difficult about recovering from jog collisions than I've become accustomed to. The really strange thing is that, when attempting to jog the robot off a collision, it'll move slightly, then stop again on the Motion Supervision fault. Normally, I would expect that I would need to clear the fault, re-engage the motors, and jog a bit more before it faults out again. Lather, rinse, repeat until I get the collision pressure off the axes.

    But on these robots, when I re-engage the motors, the robot will "jump" back to where it was previously (before I touch the joystick), undoing whatever pressure relief I managed to achieve before it faulted out. It's quite bizarre. It's almost as if the robot is trying to do a path recovery the moment the motors come on, but it shouldn't be doing that, and it just makes the situation worse. I literally got stuck in this loop for an hour one one robot before I got fed up and tried the "brake release" buttons on the side of the Joint 1 casting.

    These robots are "stock", straight from ABB with no option packages or setting customizations in the Motion parameters. The Tool and Payload ID have been done, and the correct Load data was active while this was happening. Is there a setting that we might have wrong, that could be causing this?

  • Go to Best Answer
    Quote from Skooter

    Does it have Collision Detect? It would be different to me if it didn't have it.

    613-1 Collision Detection, from the BackInfo file.

    Quote from Skooter

    I've been in that "loop" so if it's quicker and can be done safely, I've hit the brake release buttons more times than I can count (or remember).

    So, this isn't unusual? I have to say, having the robot "jump" back into the collision when the deadman is squeezed seems awfully weird. I mean, this is how it goes:

    1. Collision (motion supervision error)

    2. Clear the fault, release deadman, squeeze deadman

    3. Jog the robot away from the point of contact (simply holding the deadman without moving will cause another Motion Supervision error within a few seconds)

    4. Get a few mm of motion before the robot stops on MS error again.

    5. Release deadman, clear error, squeeze deadman

    6. before touching the joystick, robot "jumps" back, reversing the motion achieved in step 4

    • Best Answer

    We use the 6700 a lot and I would say that what you are seeing isn't that unusual. When I am in a collision like that, I have found the best way to recover it is by putting the robot in small increments and jogging it away. Once the pressure starts to release, I can normally go to medium and then turn increments off.

    I agree with bellm, I've also experienced this before. It is described in the Controller Software (IRC5) document under "What happens at a collision":

    When...then...
    the collision is detectedthe motor torques are reversed and the mechanical brakes applied in order to stop the robot
    the robot has stoppedthe robot moves in reversed direction a short distance along the path in order to remove any residual forces which may be present if a collision or jam occurred
    the residual forces are removedthe robot stops again and remains in the motors on state

    What happens is that the robot gets stuck with constant pressure on it. When you attempt to move away from the fixture, the motors reverse in an attempt to remove the residual force, but this causes it to move into the fixture. The solution of jogging away in small increments has always worked for me, but depending on the severity of the collision it may be necessary to manually release the brakes or temporarily remove the fixture itself.

    Quote from gmumaugh

    I agree with bellm, I've also experienced this before. It is described in the Controller Software (IRC5) document under "What happens at a collision":

    When...then...
    the collision is detectedthe motor torques are reversed and the mechanical brakes applied in order to stop the robot
    the robot has stoppedthe robot moves in reversed direction a short distance along the path in order to remove any residual forces which may be present if a collision or jam occurred
    the residual forces are removedthe robot stops again and remains in the motors on state

    What happens is that the robot gets stuck with constant pressure on it. When you attempt to move away from the fixture, the motors reverse in an attempt to remove the residual force, but this causes it to move into the fixture. The solution of jogging away in small increments has always worked for me, but depending on the severity of the collision it may be necessary to manually release the brakes or temporarily remove the fixture itself.

    the feature you mentioned is "path recovery option"

    Think before you talk, Read it before you think about it.

    Fran Lebowitz.

    Quote from SkyeFire

    IRB6700, IRC5, RW 6.12

    I have a set of new IRBs that are being much more difficult about recovering from jog collisions than I've become accustomed to. The really strange thing is that, when attempting to jog the robot off a collision, it'll move slightly, then stop again on the Motion Supervision fault. Normally, I would expect that I would need to clear the fault, re-engage the motors, and jog a bit more before it faults out again. Lather, rinse, repeat until I get the collision pressure off the axes.

    But on these robots, when I re-engage the motors, the robot will "jump" back to where it was previously (before I touch the joystick), undoing whatever pressure relief I managed to achieve before it faulted out. It's quite bizarre. It's almost as if the robot is trying to do a path recovery the moment the motors come on, but it shouldn't be doing that, and it just makes the situation worse. I literally got stuck in this loop for an hour one one robot before I got fed up and tried the "brake release" buttons on the side of the Joint 1 casting.

    These robots are "stock", straight from ABB with no option packages or setting customizations in the Motion parameters. The Tool and Payload ID have been done, and the correct Load data was active while this was happening. Is there a setting that we might have wrong, that could be causing this?

    This error exists in all robots. You cannot get rid of the error at the time of collision. It keeps giving an error. It comes as soon as you squeeze Deadman and make the first move. There are more than one reason for the error, the weight may be too high, the robot may be exposed to external force. I think the brake release button is a feature that saved ABB.

    Think before you talk, Read it before you think about it.

    Fran Lebowitz.

    Quote from hydra

    This error exists in all robots.

    I've never encountered it to this degree, though. And this is the first time I've ever run into a situation where the robot moves back into the collision when I'm trying to jog it away.

    I've always found ABBs to be a bit more finicky about jogging off a collision than the other brands, but this level of difficulty is new.

    Quote from hydra

    the feature you mentioned is "path recovery option"

    Is it? The section of the document I quoted was all underneath the Collision Detection [613-1] option and the Path Recovery [611-1] option is a different section. My understanding is that during a collision, the motor torques are reversed for a brief moment to attempt to remove the external force on the robot, whereas with path recovery you have to use rapid instructions to store the movement path so that you can temporarily move away, then move back to the path and continue along it.

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