Universal Robots Forum

Self Re-Teach of positions

Hello all,

I have successfully created a great pick and place, depalletizing, program for loading gears unto a conveyor. The parts are in wire baskets with 12 parts in each basket, the gripper design allows for picking up the gears and then moving the baskets. I am using the layers function to then pick and drop off the basket. All this is very successful after much time has been put into learning and trouble shooting.

Currently I am working on addressing failure modes, one being if the robot crashes it then loses its position and I have to reteach the bottom layer and all other way point positions.

question: if the robot crashes and loses these positions, is there a way to create a program that maybe uses the seek function to have the gripper go to a designated area and basically seat itself into a fixture and then use this as a datum, thus making any offsets that may be needed that would adjust all of the prior movements. basically can i have it reteach itself after a crash without manually doing this?

UR robots have true absolute encoders. Post crash, the robot knows exactly where it is unless something has physically moved the pallet relative to the robot.

In the pallet command, you can select a Feature. If you redefine the Feature, the pallet sequence will follow the movement of the Feature.

Well that’s great news! but if that is the case why have a product?

UR+ | FlexxBotics Reference for Universal robots (universal-robots.com)

The only time you’d need something like that FlexxBotics product should be when the robot base coordinate frame has shifted… i.e. you’re moving the robot around between multiple different workspaces.

Can’t see the product.

I am maybe a litle intrested, want to see the product… we do move the cobot a lot

I had this same thought when i was deploying my first UR.

I first created a reference plane using my part fixture, then created the UR waypoints relative to that plane. If i reteach the plane, the waypoints all follow.

Thanks this seems like the easiest way to doing this, the UR is on one of the movable stands that jacks up to be in place but i do have fear of it walking when running 24/7 production. I will use the conveyor or something hard set to be the reference plane to teach to.

it will not be hard mounted to the ground, it is on a movable stand with the jacks on the casters, worry is it walking over time.

You can use the visual aid offset with a Robotiq wrist, just put visual tags near the fixture and the robot will put into the correct position again.

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That’s right, you could use a vision system to realign the workspace, you could use a third party product like Flexxbotics, or you could even just do something similar yourself by adding a peg to your robot end effector and a number of holes on your “machine” that is not mechanically connected to the robot (results might not be as good as with the Flexxbotics jig but it would save you having to unmount the gripper).