Our robot will pick different materials of which the loads are not a fixed range, but can be any value between a minimum and maximum.
Before we pick it we will receive the exact wheight from a Siemens plc. Of course our gripper also has a (known) weight.
What is the right procedure to tell the robot the weight it is carrying?
At moment the robot grips the material writing this variable : $LOAD={M Mass, CM Center of gravity, J Inertia}?
Do I have to put in the $LOAD variable only the load of the material, and is the load of the gripper itself in the tooldata that I configured when commissioning the tool?
Or is the $LOAD variable for the complete weight of tool and grippedmaterial?
Different loads on gripper
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SimotionD410 -
November 24, 2017 at 1:37 PM -
Thread is marked as Resolved.
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load is not just mass, it includes inertia etc.
it includes EVERYTHING that robot holds:
1. Gripper,
2. dowel pin and Bolts attaching gripper to robot flange
3. Cables, hoses, etc.
4. product held by gripper
5. anything else that is not provided by Kukaif you change MASS for one thing (say item number 4), then INERTIA, CoG etc will also change.
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$LOAD represents the entire mass mounted to the wrist flange, including the tool and whatever payload the tool may be carrying. In some material-handling applications, where the payload mass is a significant portion of the tool mass (or even more, in some cases), the value of $LOAD needs to be changed whenever the tool picks or drops a payload.
The "shortcut" is to assign your "worst case" values to $LOAD and keep them at all times, although this will cause sub-optimal cycle times.
For payloads that vary across a large range, this becomes a non-trivial problem. If you cannot re-calculate the CoG and Inertial values of the payload on the fly, you may have to simply set some "average" or "worst-case" values for them, and only change the Mass value. If the changes are very large, you may need to find some way to re-calculate the CoG and Inertia, or set some rough "ranges" which different Mass values will fall into, and switch between them.
And if you are using an Absolute Accuracy robot, all bets are off -- AA doesn't work without completely accurate $LOAD data in all respects.
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In my case the load of the product will be at least as high as the load of the gripper itself.
If I know the center of gravity of the gripper and that of the product, and the same for the intertias.
Can they be easily added together, or is this more complicated? -
For load data assignment I use different load datas.
Load data 1 is active load which is used in motions. Second is gripper without load and third is loaded gripper. And appropriate point in program you must change the load data: LOAD_DATA[1]=LOAD_DATA[2]
It depends from your application do you need use trigger or you can use advance run stop, for change take place in right point.
If you use load data which differs greatly from actual, you get acceleration or deceleration between points. I have seen case where load fell from gripper due the wrong load data.