IRB 2600 - Inertia moment calculation

are you sure that flange connects to gripper on the smallest face (side) and not largest one (top)?

also what kind of bags we are talking about? what is the shape. using simple body shape as approximation is ok to get you close but... you still need to use correct model and apply correct transformations.

for example here are examples for computing inertia for several simple bodies:

they all show how to compute inertia about axis of rotation that passes through center of mass. and ALL of them assume that mass distribution is uniform. last of example is for slab (which is what you are trying to use).

so for gripper for example i get inertia for principal axes at CoG:

Note: it is important to keep track of axes. Length is 0.38m which is in direction of flange Z axis. but for rotation about that axis, length of that dimension is irrelevant, hence calculation for rotation about Z axis does not include Lgr. Same way rotation about Y axis does not include Wgr etc.

But this is still only inertia about center of the body and robot flange never connects to center of the body because that is inside body. If this is shifted in some direction (but still parallel) you can easily adjust by applying parallel axis theorem (Steiner theorem):

https://en.wikipedia.org/wiki/Parallel_axis_theorem

When relationship is more complex (not just parallel shift), you need to use proper transform, Steiner theorem will not help you there. An example is if gripper is attached to a robot flange with some angle, for example using V or wedge shaped adapter.

here is an example of several ways gripper and payloads could be attached. first case is what you have described - gripper is centered on flange, on its smallest face:

btw i am not ABB guy, but i skimmed over section of manual that you are referring to and there is a number of mistakes for inertia calculation.

for example L and Z are dimensions of length: Z is parallel to flange Z, and L is in direction of X. but important part here is that both of them are in meters.

Load is in kg. and inertia is in kg*m^2 so equations published in the manual are not dimensionally correct. you cannot add meters and meters squared. also brackets are not always in pairs. L2 is probably type meant to be L^2... still leaves Z that is not squared. looks like someone was trying to decide between square of sum or sum of squares and result is neither, at least for J5.

Quote

I've opened same document for smaller robot IRB-1600 and there is

J5 = Mass x ((Z + 0.065)^2 + L^2 + max (Jox, Joy) < 0.42 kgm2^2

So we can suppose that for irb 2600 it should be

J5 = Mass x ((Z + 0.085)^2 + L^2 + max (Jox, Joy) < 2.0 kgm2^2

hmmm... nope.... that is still wrong...

it again fails both dimensional check and the brackets...

L^2 cannot be there alone. that gives meters squared, not kg*m^2

i guess technical writers just use same template and the mistake just propagates with no end in sight...

something like this is plausible:

Quote

J5 = Mass x ((Z + 0.085)^2 + L^2) + max (Jox, Joy) < 2.0 kgm2^2

but it is still an example only and requires modification to fit your exact arrangement.

but you only showed how robot is mounted relative to world, not how the gripper is mounted relative to flange which is key information when computing things like this.

this is how i understood your description, so there will be a bit more work than that one equation.

:

actually no...

coordinate system orientation does not match... also Z and L are along wrong axes and not matching manual. these details matter.