Isaac Sim Contact Sensor - No Force Data

Omniverse Isaac Sim
1

I have placed contact sensors on the end-effector of ur10 with slight offset to ensure that it touches the cube in the environment.
I do get some contact data but the impulses and the forces are zero. My data looks like this when the manipulator is in contact with the cube:

{‘time’: 16.66666753590107, ‘physics_step’: 1000.0, ‘contacts’: [{‘body0’: ‘/World/UR10/wrist_3_link’, ‘body1’: ‘/World/fixed_cube’, ‘position’: array([0.10658075, 1.2599742 , 0.38374284], dtype=float32), ‘normal’: array([ 9.6200620e-06, -1.0000000e+00, -1.3767298e-06], dtype=float32), ‘impulse’: array([ 0., -0., -0.], dtype=float32)}, {‘body0’: ‘/World/UR10/wrist_3_link’, ‘body1’: ‘/World/fixed_cube’, ‘position’: array([0.10658075, 1.2599742 , 0.38374284], dtype=float32), ‘normal’: array([ 9.6200620e-06, -1.0000000e+00, -1.3767298e-06], dtype=float32), ‘impulse’: array([ 0., -0., -0.], dtype=float32)}, {‘body0’: ‘/World/UR10/wrist_3_link’, ‘body1’: ‘/World/fixed_cube’, ‘position’: array([0.10658075, 1.2599742 , 0.38374284], dtype=float32), ‘normal’: array([ 9.6200620e-06, -1.0000000e+00, -1.3767298e-06], dtype=float32), ‘impulse’: array([ 0., -0., -0.], dtype=float32)}], ‘in_contact’: False, ‘force’: 0.0, ‘number_of_contacts’: 3}

And like this when its not

{‘time’: 16.66666753590107, ‘physics_step’: 1000.0, ‘contacts’: [], ‘in_contact’: False, ‘force’: 0.0, ‘number_of_contacts’: 0}

I would like there to be force data.

Additionally, Is there a way to cover the entire UR10 with a blanket of contact sensors, so that every single part of ur10 gives me contact data?

Please let me know
Thanks!

3

Hello! the impulse is the force that the physx engine provides. In order to convert the impulse into a force, you need to divide it by your simulation timestep (usually 60 timesteps per second: 0.01666, or multiply it by 60 :)

To have any part of the UR10 with contact reporting, you can add one contact sensor per body, and set the sensor radius to -1, therefore disabling its clipping and capturing every contact that happens on the body.

4

But the impulse has 0 value :/

5

Also, what I would like to do is get contact force at every single point on ur10 and not a net force from all the contact points. Do I have to manually place multiple contact sensors for this?

6

In that case I’d suggest you use the raw data as you were before. Your zero may also be a rounding issue when printing. Try multiplying by your time steps per second to see if you get anything above zero