I am trying to figure out the units of force applied in an angular and linear drive for a joint.
I have made a 1m lever arm with a 100g weight at the end to simulate a 1Nm force, I am looking for the minimum force capable of lifting the system.
I did this in 2 of my files and I get different values for each of them
All my files have the same following parameters:
-units in cm (0.01 meter per unit in the root layer)
-magnitude = 981
the damping and stiffness of my joint are the same.
In my first file which was an empty file, it takes an angular force of 160 to lift the lever arm.
In the second file, which is my project file, I need an angular force of 10000
For the linear drive i got 1N = 16 (force set to 16 to lift 100g) in both files
What could be the cause and what parameters does the force depend on?
When I control it throught the usd project I have these settings :
To lift the cube with linear drive :
To lift the sphere with angular drive :
When I control it throught python api I delete the joint drive and use this function :
articulation.set_joint_efforts(joint_effort , joint_indice)
I get same value for both :
effort of 10000 to lift a 100g sphere at 1meter(revolute joint), cylinder’s mass is set to 1g
effort of 100 to lift a 100g cube ( prismatic joint)
Now if I try in a new empty file, with exactly the same parameters listed above, I need an effort of 160 to lift the sphere (angular drive), and 1.6 to lift the cube (linear drive)
In my previous post i said my linear effort ratio was 1N= 16 in both files:
In my emply file, i was previously in cm(root layer) with no scale on my world xform (cylinder lenth = 100 for 1m)
Now I’m still in cm(root layer) but with a 0,1 scale as shown in the previous picture (cylinder lenth = 1000 for 1m)
the x10 ratio for the linear drive should come for here. The angular ratio remain the same
As for my project file, I don’t know why it’s changed, maybe I did my test wrong beforehand.
The main fact remains that the values are not the same between the 2 files, and I don’t know where these ratios come from or whether I can rely on them.