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

import asyncio
import numpy as np
from omni.isaac.core.world import World
from omni.isaac.core.articulations import ArticulationView
from omni.isaac.core.utils.nucleus import get_assets_root_path
from omni.isaac.core.utils.stage import add_reference_to_stage

async def example():
    if World.instance():
        World.instance().clear_instance()
    world=World()
    await world.initialize_simulation_context_async()
    world.scene.add_default_ground_plane()

    # add franka articulations
    asset_path = get_assets_root_path() + "/Isaac/Robots/Franka/franka_alt_fingers.usd"
    add_reference_to_stage(usd_path=asset_path, prim_path="/World/Franka_1")
    add_reference_to_stage(usd_path=asset_path, prim_path="/World/Franka_2")

    # batch process articulations via an ArticulationView
    frankas_view = ArticulationView(prim_paths_expr="/World/Franka_[1-2]", name="frankas_view")
    world.scene.add(frankas_view)
    await world.reset_async()
    # set root body poses
    new_positions = np.array([[-1.0, 1.0, 0], [1.0, 1.0, 0]])
    frankas_view.set_world_poses(positions=new_positions)
    # set the joint positions for each articulation
    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],
                                                    [1.5, 1.5, 1.5, 1.5, 1.5, 1.5, 1.5, 1.5, 1.5]]))
asyncio.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.

          import omni
          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

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

Single DOF Position Control

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

Velocity Control

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

Single DOF Velocity Control

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

Torque Control

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

Check Object Type

from omni.isaac.dynamic_control import _dynamic_control
dc = _dynamic_control.acquire_dynamic_control_interface()

# Check to see what type of object the target prim is
obj_type = dc.peek_object_type("/Franka")
# This print statement should print ObjectType.OBJECT_ARTICULATION
print(obj_type)

Query Articulation

from omni.isaac.dynamic_control import _dynamic_control
dc = _dynamic_control.acquire_dynamic_control_interface()

# Get a handle to the Franka articulation
# This handle will automatically update if simulation is stopped and restarted
art = dc.get_articulation("/Franka")

# Get information about the structure of the articulation
num_joints = dc.get_articulation_joint_count(art)
num_dofs = dc.get_articulation_dof_count(art)
num_bodies = dc.get_articulation_body_count(art)

# Get a specific degree of freedom on an articulation
dof_ptr = dc.find_articulation_dof(art, "panda_joint2")

Read Joint State

from omni.isaac.dynamic_control import _dynamic_control
dc = _dynamic_control.acquire_dynamic_control_interface()

# Print the state of each degree of freedom in the articulation
art = dc.get_articulation("/Franka")
dof_states = dc.get_articulation_dof_states(art, _dynamic_control.STATE_ALL)
print(dof_states)

# Get state for a specific degree of freedom
dof_ptr = dc.find_articulation_dof(art, "panda_joint2")
dof_state = dc.get_dof_state(dof_ptr, _dynamic_control.STATE_ALL)
# print position for the degree of freedom
print(dof_state.pos)