Wheeled Robots [omni.isaac.wheeled_robots]
The omni.isaac.wheeled_robots extension provides controllers, utilities, and omnigraph nodes for simulating wheeled robots in isaac sim.
Basic Usage
The classes and controllers provided by omni.isaac.wheeled_robots are designed to be run within the world simulation context provided by omni.isaac.core. Like many other classes provided by core, wheeled_robots are created by wrapping prims already present on the stage in an interface class. This API is expected by world to do things like initialize and reset data structures, apply drive commands, retrieve joint states, etc…
Creating this interface means specifying the articulation being managed, the name that world will know this object by, and the names of the drivable joints
1# Assuming a stage context containing a Jetbot at /World/Jetbot
2from omni.isaac.wheeled_robots.robots import WheeledRobot
3jetbot_prim_path = "/World/Jetbot"
4
5#wrap the articulation in the interface class
6jetbot = WheeledRobot(prim_path=jetbot_prim_path,
7 name="Joan",
8 wheel_dof_names=["left_wheel_joint", "right_wheel_joint"]
9 )
Commanding the robot should be done prior to the physics step using an ArticulationAction, a type provided by omni.isaac.core to facilitate things like mixed command modes (effort, velocity, and position) and complex robots with multiple types of actions that could be taken.
1from omni.isaac.core.utils.types import ArticulationAction
2
3action = ArticulationAction(joint_velocities = np.array([1.14, 1.42]))
4jetbot.apply_wheel_actions(action)
It is rarely the case however, that a user will want to command a robot by directly manipulating the joints, and so we also provide a suite of controllers to convert various types of general commands into specific joint actions. For example, you may want to control your differential base using throttle and steering commands…
1from omni.isaac.wheeled_robots.controllers import DifferentialController
2
3throttle = 1.0
4steering = 0.5
5controller = DifferentialController(name="simple_control", wheel_radius=0.035, wheel_base=0.1)
6jetbot.apply_wheel_actions(controller.forward(throttle, steering))
Controllers
Differential Controller
- 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)
This controller uses a unicycle model of a differential drive. The Controller consumes a command in the form of a linear and angular velocity, and then computes the circular arc that satisfies this command given the distance between the wheels. This can then be used to compute the necessary angular velocities of the joints that will propell the midpoint between the wheels along the curve. The conversion is
\[ \begin{align}\begin{aligned}\omega_R = \frac{1}{2r}(2V + \omega b)\\\omega_L = \frac{1}{2r}(2V - \omega b)\end{aligned}\end{align} \]where \(\omega\) is the desired angular velocity, \(V\) is the desired linear velocity, \(r\) is the radius of the wheels, and \(b\) is the distance between them.
- 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
max_linear_speed (float) – OPTIONAL: limits the maximum linear speed that will be produced by the controller. Defaults to 1E20.
max_angular_speed (float) – OPTIONAL: limits the maximum angular speed that will be produced by the controller. Defaults to 1E20.
max_wheel_speed (float) – OPTIONAL: limits the maximum wheel speed that will be produced by the controller. Defaults to 1E20.
- forward(command: numpy.ndarray) omni.isaac.core.utils.types.ArticulationAction
convert from desired [signed linear speed, signed angular speed] to [Left Drive, Right Drive] joint targets.
- Parameters
command (np.ndarray) – desired vehicle [forward, rotation] speed
- Returns
the articulation action to be applied to the robot.
- Return type
- reset() None
Resets state of the controller.
Holonomic Controller
- 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)
This controller computes the joint drive commands required to produce the commanded forward, lateral, and yaw speeds of the robot. The problem is framed as a quadratic program to minimize the residual “net force” acting on the center of mass.
Hint
The wheel joints of the robot prim must have additional attributes to definine the roller angles and radii of the mecanum wheels.
stage = omni.usd.get_context().get_stage() joint_prim = stage.GetPrimAtPath("/path/to/wheel_joint") joint_prim.CreateAttribute("isaacmecanumwheel:radius",Sdf.ValueTypeNames.Float).Set(0.12) joint_prim.CreateAttribute("isaacmecanumwheel:angle",Sdf.ValueTypeNames.Float).Set(10.3)
The
HolonomicRobotUsdSetup
class automates this process.- 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
max_linear_speed (float) – maximum “forward” speed (default: 1.0e20)
max_angular_speed (float) – maximum “turning” speed (default: 1.0e20)
max_wheel_speed (float) – maximum “twisting” speed (default: 1.0e20)
linear_gain (float) – Multiplicative factor. How much the solver should “care” about the linear components of the solution. (default: 1.0)
linear_gain – Multiplicative factor. How much the solver should “care” about the angular components of the solution. (default: 1.0)
- build_base()
- forward(command: numpy.ndarray) omni.isaac.core.utils.types.ArticulationAction
Calculate wheel speeds given the desired signed vehicle speeds.
- Parameters
command (np.ndarray) – [forward speed, lateral speed, yaw speed].
- Returns
[description]
- Return type
- reset() None
[summary]
Wheel Base Pose Controller
- class WheelBasePoseController(name: str, open_loop_wheel_controller: omni.isaac.core.controllers.base_controller.BaseController, is_holonomic: bool = False)
This controller closes the control loop, returning the wheel commands that will drive the robot to a desired pose. It does this by exploiting an open loop controller for the robot passed at class initialization.
Hint
The logic for this controller is the following:
calculate the difference between the current position and the target position, amd compare against the postion tolerance. If the result is inside the tolerance, stop forward motion (ie. stop if closer than position tolerance)
calculate the difference between the current heading and the target heading, and compare against the heading tolerance. If the result is outside the tolerance, stop forward motion and turn to align with the target heading (ie. dont bother turning unless it’s by more than the heading tolerance)
otherwise proceed forward
- 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
Use the specified open loop controller to compute speed commands to the wheel joints of the robot that will move it towards the specified goal position
- Parameters
start_position (np.ndarray) – The current position of the robot, (X, Y, Z)
start_orientation (np.ndarray) – The current orientation quaternion of the robot, (W, X, Y, Z)
goal_position (np.ndarray) – The desired target position, (X, Y, Z)
lateral_velocity (float, optional) – How fast the robot will move forward. Defaults to 20.0.
yaw_velocity (float, optional) – How fast the robot will turn. Defaults to 0.5.
heading_tol (float, optional) – The heading tolerance. Defaults to 0.05.
position_tol (float, optional) – The position tolerance. Defaults to 4.0.
- Returns
[description]
- Return type
- reset() None
[summary]
Robots
Wheeled Robot
- class WheeledRobot(prim_path: str, name: str = 'wheeled_robot', robot_path: Optional[str] = None, wheel_dof_names: Optional[str] = None, wheel_dof_indices: Optional[int] = None, usd_path: Optional[str] = None, create_robot: Optional[bool] = False, position: Optional[numpy.ndarray] = None, orientation: Optional[numpy.ndarray] = None)
This class wraps and manages the articualtion for a two wheeled differential robot base. It is designed to be managed by the World simulation context and provides and API for applying actions, retrieving dof parameters, etc…
Creating a wheeled robot can be done in a number of different ways, depending on the use case.
Most commonly, the robot and stage are preloaded, in which case only the prim path to the articualtion root and the joint labels are required. Joint labels can take the form of either the joint names or the joint indices in the articulation.
jetbot = WheeledRobot(prim_path="/path/to/jetbot", name="Joan", wheel_dof_names=["left_wheel_joint", "right_wheel_joint"] ) armbot = WheeledRobot(prim_path="path/to/armbot" name="Weird_Arm_On_Wheels_Bot", wheel_dof_indices=[7, 8] )
Alternatively, this class can create and populate a new reference on the stage. This is done with the create_robot parameter set to True.
carter = WheeledRobot(prim_path="/desired/path/to/carter", name = "Jimmy", wheel_dof_names=["joint_wheel_left", "joint_wheel_right"], create_robot = True, usd_path = "/Isaac/Robots/Carter/nova_carter.usd", position = np.array([0,1,0]) )Hint
In all cases, either wheel_dof_names or wheel_dof_indices must be specified!
- Parameters
prim_path (str) – The stage path to the root prim of the articulation.
name ([str]) – The name used by World to identify the robot. Defaults to “wheeled_robot”
robot_path (optional[str]) – relative path from prim path to the robot.
wheel_dof_names (semi-optional[str]) – names of the wheel joints. Either this or the wheel_dof_indicies must be specified.
wheel_dof_indices – (semi-optional[int]): indices of the wheel joints in the articulation. Either this or the wheel_dof_names must be specified.
usd_path (optional[str]) – nucleus path to the robot asset. Used if create_robot is True
create_robot (bool) – create robot at prim_path using asset from usd_path. Defaults to False
position (Optional[np.ndarray], optional) – The location to create the robot when create_robot is True. Defaults to None.
orientation (Optional[np.ndarray], optional) – The orientation of the robot when crate_robot is True. 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]
- 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
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
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
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 typeArticulationController
(a Proportional-Derivative controller that can apply position targets, velocity targets and efforts) will be used
- Returns
articulation controller
- Return type
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
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
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
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: indexTo 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
List[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.]
- get_world_velocity() numpy.ndarray
Get the articulation root velocity
- Returns
current velocity of the the root prim. Shape (3,).
- Return type
np.ndarray
- 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_bodies: int
Number of articulation links
- Returns
number of links
- Return type
int
Example:
>>> prim.num_bodies 9
- 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()
orworld.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.]))
- set_world_velocity(velocity: numpy.ndarray)
Set the articulation root velocity
- Parameters
velocity (np.ndarray) – linear and angular velocity to set the root prim to. Shape (6,).
- property wheel_dof_indices
[summary]
- Returns
[description]
- Return type
int
Holonomic Robot USD Setup
- class HolonomicRobotUsdSetup(robot_prim_path: str, com_prim_path: str)
Sets up the attributes on the prims of a holonomic robot. Specifically adds the isaacmecanumwheel:radius and isaacmecanumwheel:angle attributes to the wheel joints of the robot prim
- Parameters
prim_path (str) – path of the robot articulation
com_prim_path (str) – path of the xform representing the center of mass of the vehicle
- 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
Utilities
Quintic Polynomial
- class QuinticPolynomial(xs, vxs, axs, xe, vxe, axe, time)
- calc_first_derivative(t)
- calc_point(t)
- calc_second_derivative(t)
- calc_third_derivative(t)
Quintic Polynomials Planner
- class quintic_polynomials_planner(sx, sy, syaw, sv, sa, gx, gy, gyaw, gv, ga, max_accel, max_jerk, dt)
quintic polynomials planner
- Parameters
sx (_type_) – start x position [m]
sy (_type_) – start y position [m]
syaw (_type_) – start yaw angle [rad]
sv (_type_) – start velocity [m/s]
sa (_type_) – start accel [m/ss]
gx (_type_) – goal x position [m]
gy (_type_) – goal y position [m]
gyaw (_type_) – goal yaw angle [rad]
gv (_type_) – goal velocity [m/s]
ga (_type_) – goal accel [m/ss]
max_accel (_type_) – maximum accel [m/ss]
max_jerk (_type_) – maximum jerk [m/sss]
dt (_type_) – time tick [s]
- Returns
time result rx: x position result list ry: y position result list ryaw: yaw angle result list rv: velocity result list ra: accel result list
- Return type
time
Stanly Control
- class stanley_control(state, cx, cy, cyaw, last_target_idx, p=0.5, i=0.01, d=10, k=0.5)
Stanley steering control. :param state: (State object) :param cx: ([float]) :param cy: ([float]) :param cyaw: ([float]) :param last_target_idx: (int) :return: (float, int)
PID Control
- class pid_control(target, current, Kp=0.1)
Proportional control for the speed. :param target: (float) :param current: (float) :return: (float)