May 26, 2019, 09:38:50 AM
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 Deccelerate and stop motion based on analog input

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May 14, 2019, 05:33:01 PM
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Plc_User


In a new application we should want to pick cardboard that is pilled on a pallet. Our robot wil have an analog distance sensor that will measure the distance between the gripper and the cardboard to pick on the pile. We don't have time to measure the hight of the pile when we are at te top position above the pile, but wil move continuously onto the cardboard and will gradualy reduce the speed and finally stop when the gripper is on the cardboard. This means our targetpoint will be at the bottom of the pallet and we will need to deccelerate and stop an ongoing motion based on the analog height measurement. How can this be accomplisched in a IRC5 robot?
Do we need an optional software package?

Today at 09:38:50 AM
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May 14, 2019, 05:43:42 PM
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Lemster68

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You could use the SpeedRefresh instruction, but be aware that there is a lag of about 0.3 seconds for it to take effect.  Another suggestion, why not just find the top piece and then just apply the math for the Z height change for all the subsequent positions?

May 14, 2019, 05:45:03 PM
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SAABoholic


You could do it that way but it seems a bit too complicated for what it is.

Normally you'd just keep track of the last known pick position, start your (vacuum) search 10mm above that and away you go.
The only time you search from the top would be if someone had accessed the cell (and you don't know where the top of the stack is since someone might have removed/added more sheets).

Is there a reason why you can't do it this way ?

May 14, 2019, 07:30:01 PM
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Plc_User


This installation is going to be a copy a another one, but that what with another brand of Robot. And that worked the way I described.
And yes, if a carboard is picked and there is certainty that nobody entered the cell, the hight could be remembered, but you still have the case something was changed and the robot has to search, while the pile can be 10 cm of 2m.
Or, my question is just, what are the options to deccelerate gradually and finally stop based on analog hight measurement, supposing it is not possible to know het height before the start of the motion.

May 15, 2019, 10:26:21 AM
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LEC2016


 Why couldn't you use SearchL\SStop,di""""""

May 15, 2019, 10:54:15 AM
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Plc_User


In the other application the robot approaches with relative high speed the cardboard, as soon as the analog height measurement on the gripper sees that the carboard is in its measurement range, speed is gradually decreased, and finally stopped if distance between gripper and cardboard is at picking distance. Without gradually decreasing speed, the stop point would not be precise enough.

May 15, 2019, 02:01:53 PM
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SAABoholic


So, you're not necessarily trying to solve a problem the best way possible, you just want to know how to exactly duplicate an application made with another robot brand - even if that is not the deal way of doing it with an ABB, correct ?


The problem I see is that any way I can think of to do that is going to be overly complex (analog traps, background tasks with speed refresh) and with that most likely slower than simply having a 2-output fixed trigger sensor set set at, say 150/20mm, or 200/50mm (depending on your search speed).
That way you can searchL without stop at high speed, switch to 100-200mm/s once you reach 150mm and switch to vacuum search once you reach 20mm...  that way you have a very simple code, no "extras" that can screw things up for your customer.

You can/should also skip the initial search, and just start 10-20mm higher than last known pick position, unless someone has entered the cell so I don't see how this would be any slower than an analog full range search.

Today at 09:38:50 AM
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May 15, 2019, 02:32:08 PM
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