Wheeled Robots [omni.isaac.wheeled_robots]

Controllers (Python API)

class DifferentialController(name: str, wheel_radius: float, wheel_base: float, max_linear_speed: float = 1e+20, max_angular_speed: float = 1e+20, max_wheel_speed: float = 1e+20)

Controller uses unicycle model for a differential drive

Parameters

• name (str) – [description]

• wheel_radius (float) – Radius of left and right wheels in cms

• wheel_base (float) – Distance between left and right wheels in cms

forward(command: numpy.ndarray) → omni.isaac.core.utils.types.ArticulationAction

Calculating the wheels speeds given the desired speed for the vehicle.

Parameters

command (np.ndarray) – desired vehicle [forward, rotation] speed

Returns

[description]

Return type

ArticulationAction

reset() → None

[summary]

class HolonomicController(name: str, wheel_radius: Optional[numpy.ndarray] = None, wheel_positions: Optional[numpy.ndarray] = None, wheel_orientations: Optional[numpy.ndarray] = None, mecanum_angles: Optional[numpy.ndarray] = None, wheel_axis: float = array([1, 0, 0]), up_axis: float = array([0, 0, 1]), max_linear_speed: float = 1e+20, max_angular_speed: float = 1e+20, max_wheel_speed: float = 1e+20, linear_gain: float = 1.0, angular_gain: float = 1.0)

[summary] Generic Holonomic drive controller. Model must have drive joints to mecanum wheels defined in the USD with the rollers angle and radius.

Parameters

• name (str) – [description]

• wheel_radius (np.ndarray) – radius of the wheels, array of 1 can be used if all wheels are the same size

• wheel_positions (np.ndarray) – position of the wheels relative to center of mass of the vehicle. number of wheels x [x,y,z]

• wheel_orientations (np.ndarray) – orientation of the wheels in quaternions relative to center of mass frame of the vehicle. number of wheels x [quaternions]

• mecanum_angles (np.ndarray) – mecanum wheel angles. Array of 1 can be used if all wheels have the same angle.

• wheel_axis (np.ndarray) – the spinning axis of the wheels. Defaults to [1,0,0]

• up_axis (np.ndarray) – Defaults to z- axis

build_base()

forward(command: numpy.ndarray) → omni.isaac.core.utils.types.ArticulationAction

Calculating the wheels speed given the desired vehicle speed.

Parameters

command (np.ndarray) – [forward_velocity, lateral_velocity, yaw_velocity].

Returns

[description]

Return type

ArticulationAction

reset() → None

[summary]

class WheelBasePoseController(name: str, open_loop_wheel_controller: omni.isaac.core.controllers.base_controller.BaseController, is_holonomic: bool = False)

[summary]

Parameters

• name (str) – [description]

• open_loop_wheel_controller (BaseController) – A controller that takes in a command of [longitudinal velocity, steering angle] and returns the ArticulationAction to be applied to the wheels if non holonomic. and [longitudinal velocity, latitude velocity, steering angle] if holonomic.

• is_holonomic (bool, optional) – [description]. Defaults to False.

forward(start_position: numpy.ndarray, start_orientation: numpy.ndarray, goal_position: numpy.ndarray, lateral_velocity: float = 0.2, yaw_velocity: float = 0.5, heading_tol: float = 0.05, position_tol: float = 0.04) → omni.isaac.core.utils.types.ArticulationAction

[summary]

Parameters

• start_position (np.ndarray) – [description]

• start_orientation (np.ndarray) – [description]

• goal_position (np.ndarray) – [description]

• lateral_velocity (float, optional) – [description]. Defaults to 20.0.

• yaw_velocity (float, optional) – [description]. Defaults to 0.5.

• heading_tol (float, optional) – [description]. Defaults to 0.05.

• position_tol (float, optional) – [description]. Defaults to 4.0.

Returns

[description]

Return type

ArticulationAction

reset() → None

[summary]

Utilities

class HolonomicRobotUsdSetup(robot_prim_path: str, com_prim_path: str)

[summary] Generic Holonomic Robot Setup. Extract from USD or compile from user input the necessary information for holonomic controller. :param name: [description] :type name: str :param prim_path: path of the robot articulation :type prim_path: str :param com_prim_path: path of the xform representing the center of mass of the vehicle :type com_prim_path: str

from_usd(robot_prim_path, com_prim_path)

if the USD contains all the necessary information, automatically extract them and compile

get_articulation_controller_params()

get_holonomic_controller_params()

property mecanum_angles

property up_axis

property wheel_axis

property wheel_dof_names

property wheel_orientations

property wheel_positions

property wheel_radius

class WheeledRobot(prim_path: str, robot_path: Optional[str] = None, wheel_dof_names: Optional[str] = None, wheel_dof_indices: Optional[int] = None, name: str = 'wheeled_robot', usd_path: Optional[str] = None, create_robot: Optional[bool] = False, position: Optional[numpy.ndarray] = None, orientation: Optional[numpy.ndarray] = None)

[summary]

Parameters

• prim_path (str) – [description]

• robot_path (str) – relative path from prim path to the robot.

• name (str) – [description]

• wheel_dof_names ([str, str]) – name of the wheels, [left,right].

• wheel_dof_indices – ([int, int]): indices of the wheels, [left, right]

• usd_path (str, optional) – [description]

• create_robot (bool) – create robot at prim_path if no robot exist at said path. Defaults to False

• position (Optional[np.ndarray], optional) – [description]. Defaults to None.

• orientation (Optional[np.ndarray], optional) – [description]. Defaults to None.

apply_action(control_actions: omni.isaac.core.utils.types.ArticulationAction) → None

Apply joint positions, velocities and/or efforts to control an articulation

Parameters

• control_actions (ArticulationAction) – actions to be applied for next physics step.

• indices (Optional[Union[list, np.ndarray]], optional) – degree of freedom indices to apply actions to. Defaults to all degrees of freedom.

Hint

High stiffness makes the joints snap faster and harder to the desired target, and higher damping smoothes but also slows down the joint’s movement to target

• For position control, set relatively high stiffness and low damping (to reduce vibrations)

• For velocity control, stiffness must be set to zero with a non-zero damping

• For effort control, stiffness and damping must be set to zero

Example:

>>> from omni.isaac.core.utils.types import ArticulationAction
>>>
>>> # move all the robot joints to the indicated position
>>> action = ArticulationAction(joint_positions=np.array([0.0, -1.0, 0.0, -2.2, 0.0, 2.4, 0.8, 0.04, 0.04]))
>>> prim.apply_action(action)
>>>
>>> # close the robot fingers: panda_finger_joint1 (7) and panda_finger_joint2 (8) to 0.0
>>> action = ArticulationAction(joint_positions=np.array([0.0, 0.0]), joint_indices=np.array([7, 8]))
>>> prim.apply_action(action)

apply_visual_material(visual_material: omni.isaac.core.materials.visual_material.VisualMaterial, weaker_than_descendants: bool = False) → None

Apply visual material to the held prim and optionally its descendants.

Parameters

• visual_material (VisualMaterial) – visual material to be applied to the held prim. Currently supports PreviewSurface, OmniPBR and OmniGlass.

• weaker_than_descendants (bool, optional) – True if the material shouldn’t override the descendants materials, otherwise False. Defaults to False.

Example:

>>> from omni.isaac.core.materials import OmniGlass
>>>
>>> # create a dark-red glass visual material
>>> material = OmniGlass(
...     prim_path="/World/material/glass",  # path to the material prim to create
...     ior=1.25,
...     depth=0.001,
...     thin_walled=False,
...     color=np.array([0.5, 0.0, 0.0])
... )
>>> prim.apply_visual_material(material)

apply_wheel_actions(actions: omni.isaac.core.utils.types.ArticulationAction) → None

applying action to the wheels to move the robot

Parameters

actions (ArticulationAction) – [description]

property articulation_handle: int

A handler to the articulation

The handler is a unique identifier used by the Dynamic Control extension to manage the articulation

Returns

handle

Return type

int

Example:

>>> prim.articulation_handle
1116691496961

disable_gravity() → None

Keep gravity from affecting the robot

Example:

>>> prim.disable_gravity()

property dof_names: List[str]

List of prim names for each DOF.

Returns

prim names

Return type

list(string)

Example:

>>> prim.dof_names
['panda_joint1', 'panda_joint2', 'panda_joint3', 'panda_joint4', 'panda_joint5',
 'panda_joint6', 'panda_joint7', 'panda_finger_joint1', 'panda_finger_joint2']

property dof_properties: numpy.ndarray

Articulation DOF properties

DOF properties

Index	Property name	Description
0	type	DOF type: invalid/unknown/uninitialized (0), rotation (1), translation (2)
1	hasLimits	Whether the DOF has limits
2	lower	Lower DOF limit (in radians or meters)
3	upper	Upper DOF limit (in radians or meters)
4	driveMode	Drive mode for the DOF: force (1), acceleration (2)
5	maxVelocity	Maximum DOF velocity. In radians/s, or stage_units/s
6	maxEffort	Maximum DOF effort. In N or N*stage_units
7	stiffness	DOF stiffness
8	damping	DOF damping

Returns

named NumPy array of shape (num_dof, 9)

Return type

np.ndarray

Example:

>>> # get properties for all DOFs
>>> prim.dof_properties
[(1,  True, -2.8973,  2.8973, 1, 1.0000000e+01, 5220., 60000., 3000.)
 (1,  True, -1.7628,  1.7628, 1, 1.0000000e+01, 5220., 60000., 3000.)
 (1,  True, -2.8973,  2.8973, 1, 5.9390470e+36, 5220., 60000., 3000.)
 (1,  True, -3.0718, -0.0698, 1, 5.9390470e+36, 5220., 60000., 3000.)
 (1,  True, -2.8973,  2.8973, 1, 5.9390470e+36,  720., 25000., 3000.)
 (1,  True, -0.0175,  3.7525, 1, 5.9390470e+36,  720., 15000., 3000.)
 (1,  True, -2.8973,  2.8973, 1, 1.0000000e+01,  720.,  5000., 3000.)
 (2,  True,  0.    ,  0.04  , 1, 3.4028235e+38,  720.,  6000., 1000.)
 (2,  True,  0.    ,  0.04  , 1, 3.4028235e+38,  720.,  6000., 1000.)]
>>>
>>> # property names
>>> prim.dof_properties.dtype.names
('type', 'hasLimits', 'lower', 'upper', 'driveMode', 'maxVelocity', 'maxEffort', 'stiffness', 'damping')
>>>
>>> # get DOF upper limits
>>> prim.dof_properties["upper"]
[ 2.8973  1.7628  2.8973 -0.0698  2.8973  3.7525  2.8973  0.04    0.04  ]
>>>
>>> # get the last DOF (panda_finger_joint2) upper limit
>>> prim.dof_properties["upper"][8]  # or prim.dof_properties[8][3]
0.04

enable_gravity() → None

Gravity will affect the robot

Example:

>>> prim.enable_gravity()

get_angular_velocity() → numpy.ndarray

Get the angular velocity of the root articulation prim

Returns

3D angular velocity vector. Shape (3,)

Return type

np.ndarray

Example:

>>> prim.get_angular_velocity()
[0. 0. 0.]

get_applied_action() → omni.isaac.core.utils.types.ArticulationAction

Get the last applied action

Returns

last applied action. Note: a dictionary is used as the object’s string representation

Return type

ArticulationAction

Example:

>>> # last applied action: joint_positions -> [0.0, -1.0, 0.0, -2.2, 0.0, 2.4, 0.8, 0.04, 0.04]
>>> prim.get_applied_action()
{'joint_positions': [0.0, -1.0, 0.0, -2.200000047683716, 0.0, 2.4000000953674316,
                     0.800000011920929, 0.03999999910593033, 0.03999999910593033],
 'joint_velocities': [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0],
 'joint_efforts': [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]}

get_applied_joint_efforts(joint_indices: Optional[Union[List, numpy.ndarray]] = None) → numpy.ndarray

Get the efforts applied to the joints set by the set_joint_efforts method

Parameters

joint_indices (Optional[Union[List, np.ndarray]], optional) – indices to specify which joints to read. Defaults to None (all joints)

Raises

Exception – If the handlers are not initialized

Returns

all or selected articulation joint applied efforts

Return type

np.ndarray

Example:

>>> # get all applied joint efforts
>>> prim.get_applied_joint_efforts()
[ 0.  0.  0.  0.  0.  0.  0.  0.  0.]
>>>
>>> # get finger applied efforts: panda_finger_joint1 (7) and panda_finger_joint2 (8)
>>> prim.get_applied_joint_efforts(joint_indices=np.array([7, 8]))
[0.  0.]

get_applied_visual_material() → omni.isaac.core.materials.visual_material.VisualMaterial

Return the current applied visual material in case it was applied using apply_visual_material or it’s one of the following materials that was already applied before: PreviewSurface, OmniPBR and OmniGlass.

Returns

the current applied visual material if its type is currently supported.

Return type

VisualMaterial

Example:

>>> # given a visual material applied
>>> prim.get_applied_visual_material()
<omni.isaac.core.materials.omni_glass.OmniGlass object at 0x7f36263106a0>

get_articulation_body_count() → int

Get the number of bodies (links) that make up the articulation

Returns

amount of bodies

Return type

int

Example:

>>> prim.get_articulation_body_count()
12

get_articulation_controller() → omni.isaac.core.controllers.articulation_controller.ArticulationController

Get the articulation controller

Note

If no articulation_controller was passed during class instantiation, a default controller of type ArticulationController (a Proportional-Derivative controller that can apply position targets, velocity targets and efforts) will be used

Returns

articulation controller

Return type

ArticulationController

Example:

>>> prim.get_articulation_controller()
<omni.isaac.core.controllers.articulation_controller.ArticulationController object at 0x7f04a0060190>

get_articulation_controller_properties()

get_default_state() → omni.isaac.core.utils.types.XFormPrimState

Get the default prim states (spatial position and orientation).

Returns

an object that contains the default state of the prim (position and orientation)

Return type

XFormPrimState

Example:

>>> state = prim.get_default_state()
>>> state
<omni.isaac.core.utils.types.XFormPrimState object at 0x7f33addda650>
>>>
>>> state.position
[-4.5299529e-08 -1.8347054e-09 -2.8610229e-08]
>>> state.orientation
[1. 0. 0. 0.]

get_dof_index(dof_name: str) → int

Get a DOF index given its name

Parameters

dof_name (str) – name of the DOF

Returns

DOF index

Return type

int

Example:

>>> prim.get_dof_index("panda_finger_joint2")
8

get_enabled_self_collisions() → int

Get the enable self collisions flag (physxArticulation:enabledSelfCollisions)

Returns

self collisions flag (boolean interpreted as int)

Return type

int

Example:

>>> prim.get_enabled_self_collisions()
0

get_joint_positions(joint_indices: Optional[Union[List, numpy.ndarray]] = None) → numpy.ndarray

Get the articulation joint positions

Parameters

joint_indices (Optional[Union[List, np.ndarray]], optional) – indices to specify which joints to read. Defaults to None (all joints)

Returns

all or selected articulation joint positions

Return type

np.ndarray

Example:

>>> # get all joint positions
>>> prim.get_joint_positions()
[ 1.1999920e-02 -5.6962633e-01  1.3480479e-08 -2.8105433e+00  6.8284894e-06
  3.0301569e+00  7.3234749e-01  3.9912373e-02  3.9999999e-02]
>>>
>>> # get finger positions: panda_finger_joint1 (7) and panda_finger_joint2 (8)
>>> prim.get_joint_positions(joint_indices=np.array([7, 8]))
[0.03991237  3.9999999e-02]

get_joint_velocities(joint_indices: Optional[Union[List, numpy.ndarray]] = None) → numpy.ndarray

Get the articulation joint velocities

Parameters

joint_indices (Optional[Union[List, np.ndarray]], optional) – indices to specify which joints to read. Defaults to None (all joints)

Returns

all or selected articulation joint velocities

Return type

np.ndarray

Example:

>>> # get all joint velocities
>>> prim.get_joint_velocities()
[ 1.91603772e-06 -7.67638255e-03 -2.19138826e-07  1.10636465e-02 -4.63412944e-05
  3.48245539e-02  8.84692147e-02  5.40335372e-04 1.02849208e-05]
>>>
>>> # get finger velocities: panda_finger_joint1 (7) and panda_finger_joint2 (8)
>>> prim.get_joint_velocities(joint_indices=np.array([7, 8]))
[5.4033537e-04 1.0284921e-05]

get_joints_default_state() → omni.isaac.core.utils.types.JointsState

Get the default joint states (positions and velocities).

Returns

an object that contains the default joint positions and velocities

Return type

JointsState

Example:

>>> state = prim.get_joints_default_state()
>>> state
<omni.isaac.core.utils.types.JointsState object at 0x7f04a0061240>
>>>
>>> state.positions
[ 0.012  -0.57000005  0.  -2.81  0.  3.037  0.785398  0.04  0.04 ]
>>> state.velocities
[0. 0. 0. 0. 0. 0. 0. 0. 0.]

get_joints_state() → omni.isaac.core.utils.types.JointsState

Get the current joint states (positions and velocities)

Returns

an object that contains the current joint positions and velocities

Return type

JointsState

Example:

>>> state = prim.get_joints_state()
>>> state
<omni.isaac.core.utils.types.JointsState object at 0x7f02f6df57b0>
>>>
>>> state.positions
[ 1.1999920e-02 -5.6962633e-01  1.3480479e-08 -2.8105433e+00 6.8284894e-06
  3.0301569e+00  7.3234749e-01  3.9912373e-02  3.9999999e-02]
>>> state.velocities
[ 1.91603772e-06 -7.67638255e-03 -2.19138826e-07  1.10636465e-02 -4.63412944e-05
  245539e-02  8.84692147e-02  5.40335372e-04  1.02849208e-05]

get_linear_velocity() → numpy.ndarray

Get the linear velocity of the root articulation prim

Returns

3D linear velocity vector. Shape (3,)

Return type

np.ndarray

Example:

>>> prim.get_linear_velocity()
[0. 0. 0.]

get_local_pose() → Tuple[numpy.ndarray, numpy.ndarray]

Get prim’s pose with respect to the local frame (the prim’s parent frame)

Returns

first index is the position in the local frame (with shape (3, )). Second index is quaternion orientation (with shape (4, )) in the local frame

Return type

Tuple[np.ndarray, np.ndarray]

Example:

>>> # if the prim is in position (1.0, 0.5, 0.0) with respect to the world frame
>>> position, orientation = prim.get_local_pose()
>>> position
[0. 0. 0.]
>>> orientation
[0. 0. 0.]

get_local_scale() → numpy.ndarray

Get prim’s scale with respect to the local frame (the parent’s frame)

Returns

scale applied to the prim’s dimensions in the local frame. shape is (3, ).

Return type

np.ndarray

Example:

>>> prim.get_local_scale()
[1. 1. 1.]

get_measured_joint_efforts(joint_indices: Optional[Union[List, numpy.ndarray]] = None) → numpy.ndarray

Returns the efforts computed/measured by the physics solver of the joint forces in the DOF motion direction

Parameters

joint_indices (Optional[Union[List, np.ndarray]], optional) – indices to specify which joints to read. Defaults to None (all joints)

Raises

Exception – If the handlers are not initialized

Returns

all or selected articulation joint measured efforts

Return type

np.ndarray

Example:

>>> # get all joint efforts
>>> prim.get_measured_joint_efforts()
[ 2.7897308e-06 -6.9083519e+00 -3.6398471e-06  1.9158335e+01 -4.3552645e-06
  1.1866090e+00 -4.7079347e-06  3.2339853e-04 -3.2044132e-04]
>>>
>>> # get finger efforts: panda_finger_joint1 (7) and panda_finger_joint2 (8)
>>> prim.get_measured_joint_efforts(joint_indices=np.array([7, 8]))
[ 0.0003234  -0.00032044]

get_measured_joint_forces(joint_indices: Optional[Union[List, numpy.ndarray]] = None) → numpy.ndarray

Get the measured joint reaction forces and torques (link incoming joint forces and torques) to external loads

Note

Since the name->index map for joints has not been exposed yet, it is possible to access the joint names and their indices through the articulation metadata.

prim._articulation_view._metadata.joint_names  # list of names
prim._articulation_view._metadata.joint_indices  # dict of name: index

To retrieve a specific row for the link incoming joint force/torque use joint_index + 1

Parameters

joint_indices (Optional[Union[List, np.ndarray]], optional) – indices to specify which joints to read. Defaults to None (all joints)

Raises

Exception – If the handlers are not initialized

Returns

measured joint forces and torques. Shape is (num_joint + 1, 6). Row index 0 is the incoming joint of the base link. For the last dimension the first 3 values are for forces and the last 3 for torques

Return type

np.ndarray

Example:

>>> # get all measured joint forces and torques
>>> prim.get_measured_joint_forces()
[[ 0.0000000e+00  0.0000000e+00  0.0000000e+00  0.0000000e+00  0.0000000e+00  0.0000000e+00]
 [ 1.4995076e+02  4.2574748e-06  5.6364370e-04  4.8701895e-05 -6.9072924e+00  3.1881387e-05]
 [-2.8971717e-05 -1.0677823e+02 -6.8384506e+01 -6.9072924e+00 -5.4927128e-05  6.1222494e-07]
 [ 8.7120995e+01 -4.3871860e-05 -5.5795174e+01  5.3687054e-05 -2.4538563e+01  1.3333466e-05]
 [ 5.3519474e-05 -4.8109909e+01  6.0709282e+01  1.9157074e+01 -5.9258469e-05  8.2744418e-07]
 [-3.1691040e+01  2.3313689e-04  3.9990173e+01 -5.8968733e-05 -1.1863431e+00  2.2335558e-05]
 [-1.0809851e-04  1.5340537e+01 -1.5458489e+01  1.1863426e+00  6.1094368e-05 -1.5940281e-05]
 [-7.5418940e+00 -5.0814648e+00 -5.6512990e+00 -5.6385466e-05  3.8859999e-01 -3.4943256e-01]
 [ 4.7421460e+00 -3.1945827e+00  3.5528181e+00  5.5852943e-05  8.4794536e-03  7.6405057e-03]
 [ 4.0760727e+00  2.1640673e-01 -4.0513167e+00 -5.9565349e-04  1.1407082e-02  2.1432268e-06]
 [ 5.1680198e-03 -9.7754575e-02 -9.7093947e-02 -8.4155556e-12 -1.2910691e-12 -1.9347857e-11]
 [-5.1910793e-03  9.7588278e-02 -9.7106412e-02  8.4155573e-12  1.2910637e-12 -1.9347855e-11]]
>>>
>>> # get measured joint force and torque for the fingers
>>> metadata = prim._articulation_view._metadata
>>> joint_indices = 1 + np.array([
...     metadata.joint_indices["panda_finger_joint1"],
...     metadata.joint_indices["panda_finger_joint2"],
... ])
>>> joint_indices
[10 11]
>>> prim.get_measured_joint_forces(joint_indices)
[[ 5.1680198e-03 -9.7754575e-02 -9.7093947e-02 -8.4155556e-12 -1.2910691e-12 -1.9347857e-11]
 [-5.1910793e-03  9.7588278e-02 -9.7106412e-02  8.4155573e-12  1.2910637e-12 -1.9347855e-11]]

get_sleep_threshold() → float

Get the threshold for articulations to enter a sleep state

Search for Articulations and Sleeping in PhysX docs for more details

Returns

sleep threshold

Return type

float

Example:

>>> prim.get_sleep_threshold()
0.005

get_solver_position_iteration_count() → int

Get the solver (position) iteration count for the articulation

The solver iteration count determines how accurately contacts, drives, and limits are resolved. Search for Solver Iteration Count in PhysX docs for more details.

Returns

position iteration count

Return type

int

Example:

>>> prim.get_solver_position_iteration_count()
32

get_solver_velocity_iteration_count() → int

Get the solver (velocity) iteration count for the articulation

The solver iteration count determines how accurately contacts, drives, and limits are resolved. Search for Solver Iteration Count in PhysX docs for more details.

Returns

velocity iteration count

Return type

int

Example:

>>> prim.get_solver_velocity_iteration_count()
32

get_stabilization_threshold() → float

Get the mass-normalized kinetic energy below which the articulation may participate in stabilization

Search for Stabilization Threshold in PhysX docs for more details

Returns

stabilization threshold

Return type

float

Example:

>>> prim.get_stabilization_threshold()
0.0009999999

get_visibility() → bool

Returns

true if the prim is visible in stage. false otherwise.

Return type

bool

Example:

>>> # get the visible state of an visible prim on the stage
>>> prim.get_visibility()
True

get_wheel_positions()

[summary]

Returns

[description]

Return type

Tuple[float, float]

get_wheel_velocities()

[summary]

Returns

[description]

Return type

Tuple[np.ndarray, np.ndarray]

get_world_pose() → Tuple[numpy.ndarray, numpy.ndarray]

Get prim’s pose with respect to the world’s frame

Returns

first index is the position in the world frame (with shape (3, )). Second index is quaternion orientation (with shape (4, )) in the world frame

Return type

Tuple[np.ndarray, np.ndarray]

Example:

>>> # if the prim is in position (1.0, 0.5, 0.0) with respect to the world frame
>>> position, orientation = prim.get_world_pose()
>>> position
[1.  0.5 0. ]
>>> orientation
[1. 0. 0. 0.]

get_world_scale() → numpy.ndarray

Get prim’s scale with respect to the world’s frame

Returns

scale applied to the prim’s dimensions in the world frame. shape is (3, ).

Return type

np.ndarray

Example:

>>> prim.get_world_scale()
[1. 1. 1.]

property handles_initialized: bool

Check if articulation handler is initialized

Returns

whether the handler was initialized

Return type

bool

Example:

>>> prim.handles_initialized
True

initialize(physics_sim_view=None) → None

[summary]

is_valid() → bool

Check if the prim path has a valid USD Prim at it

Returns

True is the current prim path corresponds to a valid prim in stage. False otherwise.

Return type

bool

Example:

>>> # given an existing and valid prim
>>> prims.is_valid()
True

is_visual_material_applied() → bool

Check if there is a visual material applied

Returns

True if there is a visual material applied. False otherwise.

Return type

bool

Example:

>>> # given a visual material applied
>>> prim.is_visual_material_applied()
True

property name: Optional[str]

Returns: str: name given to the prim when instantiating it. Otherwise None.

property non_root_articulation_link: bool

Used to query if the prim is a non root articulation link

Returns

True if the prim itself is a non root link

Return type

bool

Example:

>>> # for a wrapped articulation (where the root prim has the Physics Articulation Root property applied)
>>> prim.non_root_articulation_link
False

property num_dof: int

Number of DOF of the articulation

Returns

amount of DOFs

Return type

int

Example:

>>> prim.num_dof
9

post_reset() → None

[summary]

property prim: pxr.Usd.Prim

Returns: Usd.Prim: USD Prim object that this object holds.

property prim_path: str

Returns: str: prim path in the stage

set_angular_velocity(velocity: numpy.ndarray) → None

Set the angular velocity of the root articulation prim

Warning

This method will immediately set the articulation state

Parameters

velocity (np.ndarray) – 3D angular velocity vector. Shape (3,)

Hint

This method belongs to the methods used to set the articulation kinematic state:

set_linear_velocity, set_angular_velocity, set_joint_positions, set_joint_velocities, set_joint_efforts

Example:

>>> prim.set_angular_velocity(np.array([0.1, 0.0, 0.0]))

set_default_state(position: Optional[Sequence[float]] = None, orientation: Optional[Sequence[float]] = None) → None

Set the default state of the prim (position and orientation), that will be used after each reset.

Parameters

• position (Optional[Sequence[float]], optional) – position in the world frame of the prim. shape is (3, ). Defaults to None, which means left unchanged.

• orientation (Optional[Sequence[float]], optional) – quaternion orientation in the world frame of the prim. quaternion is scalar-first (w, x, y, z). shape is (4, ). Defaults to None, which means left unchanged.

Example:

>>> # configure default state
>>> prim.set_default_state(position=np.array([1.0, 0.5, 0.0]), orientation=np.array([1, 0, 0, 0]))
>>>
>>> # set default states during post-reset
>>> prim.post_reset()

set_enabled_self_collisions(flag: bool) → None

Set the enable self collisions flag (physxArticulation:enabledSelfCollisions)

Parameters

flag (bool) – whether to enable self collisions

Example:

>>> prim.set_enabled_self_collisions(True)

set_joint_efforts(efforts: numpy.ndarray, joint_indices: Optional[Union[List, numpy.ndarray]] = None) → None

Set the articulation joint efforts

Note

This method can be used for effort control. For this purpose, there must be no joint drive or the stiffness and damping must be set to zero.

Parameters

• efforts (np.ndarray) – articulation joint efforts

• joint_indices (Optional[Union[list, np.ndarray]], optional) – indices to specify which joints to manipulate. Defaults to None (all joints)

Hint

This method belongs to the methods used to set the articulation kinematic state:

set_linear_velocity, set_angular_velocity, set_joint_positions, set_joint_velocities, set_joint_efforts

Example:

>>> # set all the robot joint efforts to 0.0
>>> prim.set_joint_efforts(np.array([0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]))
>>>
>>> # set only the fingers efforts: panda_finger_joint1 (7) and panda_finger_joint2 (8) to 10
>>> prim.set_joint_efforts(np.array([10, 10]), joint_indices=np.array([7, 8]))

set_joint_positions(positions: numpy.ndarray, joint_indices: Optional[Union[List, numpy.ndarray]] = None) → None

Set the articulation joint positions

Warning

This method will immediately set (teleport) the affected joints to the indicated value. Use the apply_action method to control robot joints.

Parameters

• positions (np.ndarray) – articulation joint positions

• joint_indices (Optional[Union[list, np.ndarray]], optional) – indices to specify which joints to manipulate. Defaults to None (all joints)

Hint

This method belongs to the methods used to set the articulation kinematic state:

set_linear_velocity, set_angular_velocity, set_joint_positions, set_joint_velocities, set_joint_efforts

Example:

>>> # set all the robot joints
>>> prim.set_joint_positions(np.array([0.0, -1.0, 0.0, -2.2, 0.0, 2.4, 0.8, 0.04, 0.04]))
>>>
>>> # set only the fingers in closed position: panda_finger_joint1 (7) and panda_finger_joint2 (8) to 0.0
>>> prim.set_joint_positions(np.array([0.04, 0.04]), joint_indices=np.array([7, 8]))

set_joint_velocities(velocities: numpy.ndarray, joint_indices: Optional[Union[List, numpy.ndarray]] = None) → None

Set the articulation joint velocities

Warning

This method will immediately set the affected joints to the indicated value. Use the apply_action method to control robot joints.

Parameters

• velocities (np.ndarray) – articulation joint velocities

• joint_indices (Optional[Union[list, np.ndarray]], optional) – indices to specify which joints to manipulate. Defaults to None (all joints)

Hint

This method belongs to the methods used to set the articulation kinematic state:

set_linear_velocity, set_angular_velocity, set_joint_positions, set_joint_velocities, set_joint_efforts

Example:

>>> # set all the robot joint velocities to 0.0
>>> prim.set_joint_velocities(np.array([0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]))
>>>
>>> # set only the fingers velocities: panda_finger_joint1 (7) and panda_finger_joint2 (8) to -0.01
>>> prim.set_joint_velocities(np.array([-0.01, -0.01]), joint_indices=np.array([7, 8]))

set_joints_default_state(positions: Optional[numpy.ndarray] = None, velocities: Optional[numpy.ndarray] = None, efforts: Optional[numpy.ndarray] = None) → None

Set the joint default states (positions, velocities and/or efforts) to be applied after each reset.

Note

The default states will be set during post-reset (e.g., calling .post_reset() or world.reset() methods)

Parameters

• positions (Optional[np.ndarray], optional) – joint positions. Defaults to None.

• velocities (Optional[np.ndarray], optional) – joint velocities. Defaults to None.

• efforts (Optional[np.ndarray], optional) – joint efforts. Defaults to None.

Example:

>>> # configure default joint states
>>> prim.set_joints_default_state(
...     positions=np.array([0.0, -1.0, 0.0, -2.2, 0.0, 2.4, 0.8, 0.04, 0.04]),
...     velocities=np.zeros(shape=(prim.num_dof,)),
...     efforts=np.zeros(shape=(prim.num_dof,))
... )
>>>
>>> # set default states during post-reset
>>> prim.post_reset()

set_linear_velocity(velocity: numpy.ndarray) → None

Set the linear velocity of the root articulation prim

Warning

This method will immediately set the articulation state

Parameters

velocity (np.ndarray) – 3D linear velocity vector. Shape (3,).

Hint

This method belongs to the methods used to set the articulation kinematic state:

set_linear_velocity, set_angular_velocity, set_joint_positions, set_joint_velocities, set_joint_efforts

Example:

>>> prim.set_linear_velocity(np.array([0.1, 0.0, 0.0]))

set_local_pose(translation: Optional[Sequence[float]] = None, orientation: Optional[Sequence[float]] = None) → None

Set prim’s pose with respect to the local frame (the prim’s parent frame).

Warning

This method will change (teleport) the prim pose immediately to the indicated value

Parameters

• translation (Optional[Sequence[float]], optional) – translation in the local frame of the prim (with respect to its parent prim). shape is (3, ). Defaults to None, which means left unchanged.

• orientation (Optional[Sequence[float]], optional) – quaternion orientation in the local frame of the prim. quaternion is scalar-first (w, x, y, z). shape is (4, ). Defaults to None, which means left unchanged.

Hint

This method belongs to the methods used to set the prim state

Example:

>>> prim.set_local_pose(translation=np.array([1.0, 0.5, 0.0]), orientation=np.array([1., 0., 0., 0.]))

set_local_scale(scale: Optional[Sequence[float]]) → None

Set prim’s scale with respect to the local frame (the prim’s parent frame).

Parameters

scale (Optional[Sequence[float]]) – scale to be applied to the prim’s dimensions. shape is (3, ). Defaults to None, which means left unchanged.

Example:

>>> # scale prim 10 times smaller
>>> prim.set_local_scale(np.array([0.1, 0.1, 0.1]))

set_sleep_threshold(threshold: float) → None

Set the threshold for articulations to enter a sleep state

Search for Articulations and Sleeping in PhysX docs for more details

Parameters

threshold (float) – sleep threshold

Example:

>>> prim.set_sleep_threshold(0.01)

set_solver_position_iteration_count(count: int) → None

Set the solver (position) iteration count for the articulation

The solver iteration count determines how accurately contacts, drives, and limits are resolved. Search for Solver Iteration Count in PhysX docs for more details.

Warning

Setting a higher number of iterations may improve the fidelity of the simulation, although it may affect its performance.

Parameters

count (int) – position iteration count

Example:

>>> prim.set_solver_position_iteration_count(64)

set_solver_velocity_iteration_count(count: int)

Set the solver (velocity) iteration count for the articulation

The solver iteration count determines how accurately contacts, drives, and limits are resolved. Search for Solver Iteration Count in PhysX docs for more details.

Warning

Setting a higher number of iterations may improve the fidelity of the simulation, although it may affect its performance.

Parameters

count (int) – velocity iteration count

Example:

>>> prim.set_solver_velocity_iteration_count(64)

set_stabilization_threshold(threshold: float) → None

Set the mass-normalized kinetic energy below which the articulation may participate in stabilization

Search for Stabilization Threshold in PhysX docs for more details

Parameters

threshold (float) – stabilization threshold

Example:

>>> prim.set_stabilization_threshold(0.005)

set_visibility(visible: bool) → None

Set the visibility of the prim in stage

Parameters

visible (bool) – flag to set the visibility of the usd prim in stage.

Example:

>>> # make prim not visible in the stage
>>> prim.set_visibility(visible=False)

set_wheel_positions(positions) → None

[summary]

Parameters

positions (Tuple[float, float]) – [description]

set_wheel_velocities(velocities) → None

[summary]

Parameters

velocities (Tuple[float, float]) – [description]

set_world_pose(position: Optional[Sequence[float]] = None, orientation: Optional[Sequence[float]] = None) → None

Ses prim’s pose with respect to the world’s frame

Warning

This method will change (teleport) the prim pose immediately to the indicated value

Parameters

• position (Optional[Sequence[float]], optional) – position in the world frame of the prim. shape is (3, ). Defaults to None, which means left unchanged.

• orientation (Optional[Sequence[float]], optional) – quaternion orientation in the world frame of the prim. quaternion is scalar-first (w, x, y, z). shape is (4, ). Defaults to None, which means left unchanged.

Hint

This method belongs to the methods used to set the prim state

Example:

>>> prim.set_world_pose(position=np.array([1.0, 0.5, 0.0]), orientation=np.array([1., 0., 0., 0.]))

property wheel_dof_indices

[summary]

Returns

[description]

Return type

int

Omnigraph Nodes

DifferentialController

Differential Controller

Use the wheel radius and the distance between the wheels to calculate the desired wheels speed when given a desired vehicle speed.

Inputs

• execIn (execution): The input execution.

• wheelRadius (double): radius of the wheels.

• wheelDistance (double): distance between the two wheels.

• maxLinearSpeed (double): max linear speed allowed for vehicle.

• maxAngularSpeed (double): max angular speed allowed for vehicle.

• maxWheelSpeed (double): max wheel speed allowed.

• linearVelocity (double): desired linear velocity.

• angularVelocity (double): desired rotation velocity.

Outputs

• positionCommand (double[]): position commands.

• velocityCommand (double[]): velocity commands.

• effortCommand (double[]): effort commands.

QuinticPathPlanner

Quintic Path Planner For Wheeled robots

Use odometry from a robot and a target position/prim to calculate a route from the robot’s starting position to the target position.

Inputs

• execIn (execution): The input execution.

• currentPosition (vectord[3]): Current position of the robot (recommended to use Get Prim Local to World Transform node).

• currentOrientation (quatd[4]): Current rotation of the robot as a quaternion (recommended to use Get Prim Local to World Transform node).

• targetPrim (target, optional): USD prim reference to the goal position/orientation prim.

• targetPosition (vectord[3]): Target position (used if no targetPrim provided).

• targetOrientation (quatd[4]): Target orientation (used if no targetPrim provided).

• initialVelocity (double): Initial velocity. Default to 0.5.

• initialAccel (double): Initial acceleration. Default to 0.02.

• goalVelocity (double): Goal velocity. Default to 0.5.

• goalAccel (double): Goal acceleration. Default to 0.02.

• maxAccel (double): Max acceleration. Default to 1.5.

• maxJerk (double): Max jerk. Default to 0.3.

• step (double): Step. Default to 0.16666666667.

Outputs

• execOut (execution): The output execution.

• pathArrays (double[]): The path v, x, y, and yaw arrays.

• target (double[3]): Target position and orientation.

• targetChanged (bool): Target position/orientation has changed.

HolonomicController

Holonomic Controller

Calculating the desired wheel speeds when given a desired vehicle speed.

Inputs

• execIn (execution): The input execution.

• wheelRadius (double[]): an array of wheel radius.

• wheelPositions (double[3][]): position of the wheel with respect to chassis’ center of mass.

• wheelOrientations (double[4][]): orientation of the wheel with respect to chassis’ center of mass frame.

• mecanumAngles (double[]): angles of the mecanum wheels with respect to wheel’s rotation axis.

• wheelAxis (double[3]): the rotation axis of the wheels.

• upAxis (double[3]): the rotation axis of the vehicle.

• velocityCommands ([‘float[3]’, ‘double[3]’]): velocity in x and y and rotation.

• maxLinearSpeed (double, optional): maximum speed allowed for the vehicle.

• maxAngularSpeed (double, optional): maximum angular rotation speed allowed for the vehicle.

• maxWheelSpeed (double, optional): maximum rotation speed allowed for the wheel joints.

• linearGain (double): linear gain. Default to 1.

• angularGain (double): angular gain. Default to 1.

Outputs

• jointPositionCommand (double[]): position commands for the wheel joints.

• jointVelocityCommand (double[]): velocity commands for the wheels joints.

• jointEffortCommand (double[]): effort commands for the wheels joints.

StanleyControlPID

Drive to Target Steering

Inputs

• execIn (execution): The input execution.

• currentPosition (vectord[3]): Current position of the robot (recommended to use Get Prim Local to World Transform node).

• currentOrientation (quatd[4]): Current rotation of the robot as a quaternion (recommended to use Get Prim Local to World Transform node).

• currentSpeed (vectord[3]): Current linear velocity of the robot.

• maxVelocity (double): Maximum linear velocity of the robot. Default to 1.5.

• reachedGoal (bool[]): Position and orientation thresholds at target. Default to [False, False].

• pathArrays (double[]): The path v, x, y, and yaw arrays.

• target (double[3]): Target position and orientation. Default to [0, 0, 0].

• targetChanged (bool): Target position/orientation has changed. Default to False.

• wheelBase (double): Distance between the centers of the front and rear wheels. Default to 0.4132.

• thresholds (double[2]): Position and orientation thresholds at target. Default to [0.1, 0.1].

• drawPath (bool): Draw the provided path curve onto the stage. Default to False.

• step (double): Step. Default to 0.16666666667.

• gains (double[3]): control, velocity and steering gains. Default to [0.5, 0.1, 0.0872665].

Outputs

• execOut (execution): The output execution.

• linearVelocity (double): Current forward speed for robot drive.

• angularVelocity (double): Current angular speed for robot drive.

HolonomicRobotUsdSetup

setup any robot to be ready to be used by the holonomic controller by extract attributes from USD

Use this node to extract all the holonomic drive information from USD if the listed information are stored in the USD file already. If they are not in USD, you can manually set those values in the HolonomicController node

Inputs

• robotPrim (target): prim for the robot’s articulation root.

• comPrim (target): prim for the center of mass xform.

• usePath (bool): use prim path instead of prim target. Default to False.

• robotPrimPath (token): prim path to the robot’s articulation root link when usdPath is true.

• comPrimPath (token): prim path to the robot’s center of mass xform.

Outputs

• wheelRadius (double[]): an array of wheel radius.

• wheelPositions (double[3][]): position of the wheel with respect to chassis’ center of mass.

• wheelOrientations (double[4][]): orientation of the wheel with respect to chassis’ center of mass frame.

• mecanumAngles (double[]): angles of the mechanum wheels with respect to wheel’s rotation axis.

• wheelAxis (double[3]): the rotation axis of the wheels, assuming all wheels have the same.

• upAxis (double[3]): the rotation axis of the vehicle.

• wheelDofNames (token[]): name of the left wheel joint.

CheckGoal2D

Check if wheeled robot has reached goal

Inputs

• execIn (execution): The input execution.

• currentPosition (vectord[3]): Current position of the robot (recommended to use Get Prim Local to World Transform node).

• currentOrientation (quatd[4]): Current rotation of the robot as a quaternion (recommended to use Get Prim Local to World Transform node).

• target (double[3]): Target position and orientation. Default to [0, 0, 0].

• targetChanged (bool): Target position/orientation has changed. Default to False.

• thresholds (double[2]): Position and orientation thresholds at target. Default to [0.1, 0.1].

Outputs

• execOut (execution): The output execution.

• reachedGoal (bool[]): Reached position and orientation goals.

AckermannSteering

Ackermann Steering Geometry

Inputs

• execIn (execution): The input execution.

• acceleration (double): Desired forward acceleration for the robot in m/s^2.

• speed (double): Desired forward speed in m/s.

• steeringAngle (double): Desired virtual angle in radians. Corresponds to the yaw of a virtual wheel located at the center of the front axle. By default it is positive for turning left and negative for turning right for front wheel drive. Default to 0.0.

• currentLinearVelocity (vectord[3]): Current linear velocity of the robot in m/s.

• wheelBase (double): Distance between the front and rear axles of the robot in meters.

• trackWidth (double): Distance between the left and right rear wheels of the robot in meters.

• turningWheelRadius (double): Radius of the front wheels of the robot in meters.

• maxWheelVelocity (double): Maximum angular velocity of the robot wheel in rad/s.

• invertSteeringAngle (bool): Flips the sign of the steering angle, Set to true for rear wheel steering.

• useAcceleration (bool): Use acceleration as an input, Set to false to use speed as input instead. Default to True.

• maxWheelRotation (double): Maximum angle of rotation for the front wheels in radians.

• DT (double): Delta time for the simulation step.

Outputs

• execOut (execution): The output execution.

• leftWheelAngle (double): Angle for the left turning wheel in degrees.

• rightWheelAngle (double): Angle for the right turning wheel in degrees.

• wheelRotationVelocity (double): Angular velocity for the turning wheels in rad/s.