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How to prevent YuMi arms from going limp during e-stop or joint load error?

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LeonL
LeonL ✭
edited July 2019 in Collaborative Robots
The YuMi has a payload of 0.5kg and I am using the stock ABB grippers (one vacuum/grippers/camera) with some modified grippers which weigh ~70 grams a pair. The arm with the modified grippers move to a location and pick up a fixture/payload which weighs ~300 grams. I am having problems with the gripper moving the payload to its destination and am receiving "joint load too high" errors which causes the arm to stop, however the joints closest to the gripper go limp during this error which causes the objects resting on the fixture/payload to fall off the fixture and onto the ground. These parts are expensive so we cannot afford the robot to drop the parts. Is there a setting on the controller which completely seizes the motors during this 'joint load' error such that joints don't just give out and go limp? This problem also occurs if the arm is carrying parts and the e-stop is engaged. When moving the fixtures, I am using a 'MoveJ' instruction with a speed of 'v200' and zonedata value of 'fine'.

I have tried lowering the sensitivity of motion supervision for the arm as well as adjusting the tooldata weight for the modified grippers. What can I do to prevent this undesired behavior?
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  • graemepaulin
    graemepaulin mod
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    The tooldata must have the correct mass of the complete gripper (gripper without fingers is listed as 239.5 g plus 70 grams for your fingers = 309.5 g) - also the center of gravity and inertia values for best motion.

    When you pick up the load use the command GripLoad "the load name" - the load data must have the correct mass (300 g) - as for tooldata center of gravity and inertia for best motion.

    The total needs to be below the maximum payload of Yumi which as you say is 500 g -> you are over this by 39.5 g.

    You should ask you local ABB to find out from the factory support if this overload is acceptable and if so what restrictions there are on acceleration, etc.

  • LeonL
    LeonL ✭
    edited July 2019
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    graemepaulin said:

    The tooldata must have the correct mass of the complete gripper (gripper without fingers is listed as 239.5 g plus 70 grams for your fingers = 309.5 g) - also the center of gravity and inertia values for best motion.

    When you pick up the load use the command GripLoad "the load name" - the load data must have the correct mass (300 g) - as for tooldata center of gravity and inertia for best motion.

    The total needs to be below the maximum payload of Yumi which as you say is 500 g -> you are over this by 39.5 g.

    You should ask you local ABB to find out from the factory support if this overload is acceptable and if so what restrictions there are on acceleration, etc.


    Let's say the payload was light enough to be under the 500 g limit. What do I need to do in order to fully engage brakes and prevent tipping when the e-stop is engaged or one of the joints closest to the grippers senses too high of a torque value?
  • graemepaulin
    graemepaulin mod
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    I do not think you will be able to stop this happening for the e-stop, but for the other errors you may be able to trap them by error code and then stop the movement but not go motors off.

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