coordinates inconsistency


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So I am performing a pick and place with sawyer. it is picking up 3 items and placing each in a box. I have the 3 items centered around Sawyer's coordinates. the first item is at like x = -200 y = 460, second is x = 0 y = 460 and the third x = 200 and y = 460. Everything runs fine for a few cycles and then the x dimension will shift with no reason, all of a sudden its off by 4mm but it says that the coordinates are still -200, 0 and 200. I have the coordinates taped out so physically nothing is changing, it seems as tho the dimensions of which sawyer is sitting on within the program are changing.

I have the newest version of intera, I have the picks and the places slowed down completely and the approaches are matching the picks. It seems like sawyer is getting lost within itself with each movement. I'm wondering if there is something going on with my Sawyer itself or if there is a bug in the newest software???

Please Help!!!!


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  • 1 month later...

I'm having the same issue. The best run I got was 10 hours then I get a call saying that it was missing its pick/place points.

At one point I thought maybe it was a duty cycle issue (i.e. the arm heated up & expanded) so we shut down the robot and then booted it back up after about an hour and it was still going to the same, incorrect points.

I marked off the pad locations on the base but it doesn't look like the robot has been jostled or moved.

At another point I thought that a crash had thrown off the encoders somehow but in this latest series of miss-picks/places the robot didn't crash before it started missing its points so that ruled that out.

Each time it misses, I always end up having to shift along the x-axis  by 1-4 mm.

My theory right now is that since just about all of my positions are based on a landmark tag, maybe the fact that that's a variable plane is screwing with things (I am not actively using the landmark as part of daily operation I just have it there as a backup in case anything shifts so I can recover without a whole lot of effort). I just re-assigned the parent on all my points to the base frame (a static reference might help I'm hoping) but I won't know if that works for another 10 hours if history is any indicator.


Are you using the landmark system or are you using the base frame as the parent to your points?

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I built a frame out of 80/20 and mounted it directly to Sawyer so it's physically impossible for Sawyer to move from it's pick and place locations. I have a Harmo robot placing objects onto the frame and Sawyer puts them into boxes that are also on the same frame.  I had problems with getting the landmark to work in the beginning so I've never used it since.

I was never able to figure it out. The first time it happened I recalibrated and it remained the same. The origin seemed to have shifted in the x-direction.  So I thought ok, it must be either within Sawyer's encoders or maybe there is something weird in my program. I remade the program and it's origin was still off from the previous time but I continued on. When it did it shifted the second time, I never recalibrated, I just deleted the program and made a whole new one (very frustrating) but it went back to the previously shifted position, not the original origin from when I started programming it. I haven't ran it that much since, so I am not sure if it will do it again. Hopefully next week I will have my one of my end effectors made so that I can run for a while and see what happens.

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I was able to resolve this issue!

I had been making modifications to the end of arm tooling since handing the robot over to production. It turns out I had added something like 214g and all my xyz center of mass coordinates were off because of those changes.

I re-weighed my tooling, update the mass in the tooling library and corrected the center of mass coordinates on the fly by just using the zero-g button and seeing which way the robot was pulling. Since then I haven't had any issue with lost coordinates in my program. I hope this helps!

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