Robot Simulation

Note

The following scripts should only be run on the default new stage and only once. You can try these by creating a new stage via File->New and running from Window-> Script Editor

Create Articulations and ArticulationView

The following snippet adds two Franka articulations to the scene and creates a view object to manipulate their properties in parallel

 1import asyncio
 2import numpy as np
 3from omni.isaac.core.world import World
 4from omni.isaac.core.articulations import ArticulationView
 5from omni.isaac.core.utils.nucleus import get_assets_root_path
 6from omni.isaac.core.utils.stage import add_reference_to_stage
 7
 8async def example():
 9    if World.instance():
10        World.instance().clear_instance()
11    world=World()
12    await world.initialize_simulation_context_async()
13    world.scene.add_default_ground_plane()
14
15    # add franka articulations
16    asset_path = get_assets_root_path() + "/Isaac/Robots/Franka/franka_alt_fingers.usd"
17    add_reference_to_stage(usd_path=asset_path, prim_path="/World/Franka_1")
18    add_reference_to_stage(usd_path=asset_path, prim_path="/World/Franka_2")
19
20    # batch process articulations via an ArticulationView
21    frankas_view = ArticulationView(prim_paths_expr="/World/Franka_[1-2]", name="frankas_view")
22    world.scene.add(frankas_view)
23    await world.reset_async()
24    # set root body poses
25    new_positions = np.array([[-1.0, 1.0, 0], [1.0, 1.0, 0]])
26    frankas_view.set_world_poses(positions=new_positions)
27    # set the joint positions for each articulation
28    frankas_view.set_joint_positions(np.array([[1.5, 1.5, 1.5, 1.5, 1.5, 1.5, 1.5, 1.5, 1.5],
29                                                    [1.5, 1.5, 1.5, 1.5, 1.5, 1.5, 1.5, 1.5, 1.5]]))
30asyncio.ensure_future(example())

See the API Documentation for all the possible operations supported by ArticulationView.

Joints Control

To run the following code snippets:

  1. The following code snippets assume that the Stage contains a Franka robot at the /Franka prim path. Go to the top menu bar and click Create > Isaac > Robots > From Library > Manipulators > Franka to add a Franka to the scene.

  2. At least one frame of simulation must occur before the Dynamic Control APIs work correctly. To start the simulation:

    1. (Option #1) Press the PLAY button to begin simulating.

    2. (Option #2) Use the following code snippet to start the simulation using the Python API before running any of the snippets below.

      1    import omni
2    omni.timeline.get_timeline_interface().play()

We recommend using the built-in Script Editor to test these snippets. For deeper development, please see the Isaac Sim Workflows tutorial.

To access the Script Editor, go to the top menu bar and click Window > Script Editor.

Note

The snippets are disparate examples, running them out of order may have unintended consequences.

Note

The snippets are for demonstrative purposes, the resulting movements may not respect the robot’s kinematic limitations.

Position Control

1from omni.isaac.dynamic_control import _dynamic_control
2import numpy as np
3dc = _dynamic_control.acquire_dynamic_control_interface()
4articulation = dc.get_articulation("/Franka")
5# Call this each frame of simulation step if the state of the articulation is changing.
6dc.wake_up_articulation(articulation)
7joint_angles = [np.random.rand(9) * 2 - 1]
8dc.set_articulation_dof_position_targets(articulation, joint_angles)

Single DOF Position Control

1from omni.isaac.dynamic_control import _dynamic_control
2import numpy as np
3dc = _dynamic_control.acquire_dynamic_control_interface()
4articulation = dc.get_articulation("/Franka")
5dc.wake_up_articulation(articulation)
6dof_ptr = dc.find_articulation_dof(articulation, "panda_joint2")
7dc.set_dof_position_target(dof_ptr, -1.5)

Velocity Control

 1from pxr import UsdPhysics
 2stage = omni.usd.get_context().get_stage()
 3for prim in stage.TraverseAll():
 4    prim_type = prim.GetTypeName()
 5    if prim_type in ["PhysicsRevoluteJoint" , "PhysicsPrismaticJoint"]:
 6        if prim_type == "PhysicsRevoluteJoint":
 7            drive = UsdPhysics.DriveAPI.Get(prim, "angular")
 8        else:
 9            drive = UsdPhysics.DriveAPI.Get(prim, "linear")
10        drive.GetStiffnessAttr().Set(0)
11from omni.isaac.dynamic_control import _dynamic_control
12import numpy as np
13dc = _dynamic_control.acquire_dynamic_control_interface()
14#Note: getting the articulation has to happen after changing the drive stiffness
15articulation = dc.get_articulation("/Franka")
16dc.wake_up_articulation(articulation)
17joint_vels = [-np.random.rand(9)*10]
18dc.set_articulation_dof_velocity_targets(articulation, joint_vels)

Single DOF Velocity Control

 1from pxr import UsdPhysics
 2stage = omni.usd.get_context().get_stage()
 3panda_joint2_drive = UsdPhysics.DriveAPI.Get(stage.GetPrimAtPath("/Franka/panda_link1/panda_joint2"), "angular")
 4panda_joint2_drive.GetStiffnessAttr().Set(0)
 5from omni.isaac.dynamic_control import _dynamic_control
 6import numpy as np
 7dc = _dynamic_control.acquire_dynamic_control_interface()
 8#Note: getting the articulation has to happen after changing the drive stiffness
 9articulation = dc.get_articulation("/Franka")
10dc.wake_up_articulation(articulation)
11dof_ptr = dc.find_articulation_dof(articulation, "panda_joint2")
12dc.set_dof_velocity_target(dof_ptr, 0.2)

Torque Control

1from omni.isaac.dynamic_control import _dynamic_control
2import numpy as np
3dc = _dynamic_control.acquire_dynamic_control_interface()
4articulation = dc.get_articulation("/Franka")
5dc.wake_up_articulation(articulation)
6joint_efforts = [-np.random.rand(9) * 1000]
7dc.set_articulation_dof_efforts(articulation, joint_efforts)

Check Object Type

1from omni.isaac.dynamic_control import _dynamic_control
2dc = _dynamic_control.acquire_dynamic_control_interface()
3
4# Check to see what type of object the target prim is
5obj_type = dc.peek_object_type("/Franka")
6# This print statement should print ObjectType.OBJECT_ARTICULATION
7print(obj_type)

Query Articulation

 1from omni.isaac.dynamic_control import _dynamic_control
 2dc = _dynamic_control.acquire_dynamic_control_interface()
 3
 4# Get a handle to the Franka articulation
 5# This handle will automatically update if simulation is stopped and restarted
 6art = dc.get_articulation("/Franka")
 7
 8# Get information about the structure of the articulation
 9num_joints = dc.get_articulation_joint_count(art)
10num_dofs = dc.get_articulation_dof_count(art)
11num_bodies = dc.get_articulation_body_count(art)
12
13# Get a specific degree of freedom on an articulation
14dof_ptr = dc.find_articulation_dof(art, "panda_joint2")

Read Joint State

 1from omni.isaac.dynamic_control import _dynamic_control
 2dc = _dynamic_control.acquire_dynamic_control_interface()
 3
 4# Print the state of each degree of freedom in the articulation
 5art = dc.get_articulation("/Franka")
 6dof_states = dc.get_articulation_dof_states(art, _dynamic_control.STATE_ALL)
 7print(dof_states)
 8
 9# Get state for a specific degree of freedom
10dof_ptr = dc.find_articulation_dof(art, "panda_joint2")
11dof_state = dc.get_dof_state(dof_ptr, _dynamic_control.STATE_ALL)
12# print position for the degree of freedom
13print(dof_state.pos)