[isaacsim.robot_setup.assembler] Robot Assembler

Version: 3.0.3

Alpha version of Robot Assembler Extension: Assemble multiple Articulations into a single robot

Enable Extension

The extension can be enabled (if not already) in one of the following ways:

Command-line interface

Define the next entry as an application argument from a terminal.

APP_SCRIPT.(sh|bat) --enable isaacsim.robot_setup.assembler

Experience/extension configuration

Define the next entry under [dependencies] in an experience (.kit) file or an extension configuration (extension.toml) file.

[dependencies]
"isaacsim.robot_setup.assembler" = {}

Extension Manager UI

Open the Window > Extensions menu in a running application instance and search for isaacsim.robot_setup.assembler. Then, toggle the enable control button if it is not already active.

API

Python API

RobotAssembler	RobotAssembler is a class to assemble robots from a base robot and an attachment robot.
AssembledRobot
AssembledBodies	Class representing two assembled rigid bodies connected by a fixed joint.

class RobotAssembler

Bases: object

RobotAssembler is a class to assemble robots from a base robot and an attachment robot. It will create a new USD stage with the assembly and configure a variant selection to enable the attachment robot to be selected. If the variant set already exists in the source asset, it creates a new entry to it, otherwise it creates a new variant set.

assemble()

Composes the attachment robot onto the base robot, so that the attachment robot is a child of the base robot, and ready to simulate

assemble_articulations(

base_robot_path: str,

attach_robot_path: str,

base_robot_mount_frame: str,

attach_robot_mount_frame: str,

mask_all_collisions=True,

single_robot=False,

refresh_asset_paths: bool = False,

) → AssembledRobot

Compose two robots into one physical structure

Parameters:

• base_robot_path (str) – Path to base robot.

• attach_robot_path (str) – Path to attach robot. The attach robot will be unrooted from the stage and attached only to the base robot

• base_robot_mount_frame (str) – Relative path to frame in base robot where there is the desired attach point.

• attach_robot_mount_frame (str) – Relative path to frame in the attach robot where there is the desired attach point.

• mask_all_collisions (bool, optional) – Mask all collisions between attach robot and base robot. This is necessary when setting single_robot=False to prevent Physics constraint violations from the new fixed joint. Advanced users may set this flag to False and use the mask_collisions() function separately for more customizable behavior. Defaults to True.

• single_robot (bool, optional) – If True: control the resulting composed robots as a single robot Articulation at base_robot_path. Setting this flag to True may resolve unstable physics behavior when teleporting the robot base. Defaults to False.

Returns:

An object representing the assembled robot. This object can detach the composed robots and edit the fixed joint transform.

Return type:

AssembledRobot

assemble_rigid_bodies(

base_path: str,

attach_path: str,

base_mount_frame: str,

attach_mount_frame: str,

mask_all_collisions: bool = True,

refresh_asset_paths: bool = False,

) → AssembledBodies

Assemble two rigid bodies into one physical structure

Parameters:

• base_robot_path (str) – Path to base robot.

• attach_robot_path (str) – Path to attach robot. The attach robot will be unrooted from the stage and attached only to the base robot

• base_robot_mount_frame (str) – Relative path to frame in base robot where there is the desired attach point.

• attach_robot_mount_frame (str) – Relative path to frame in the attach robot where there is the desired attach point.

• mask_all_collisions (bool, optional) – Mask all collisions between attach robot and base robot. This is necessary when setting single_robot=False to prevent Physics constraint violations from the new fixed joint. Advanced users may set this flag to False and use the mask_collisions() function separately for more customizable behavior. Defaults to True.

Returns:

An object representing the assembled bodies. This object can detach the composed robots and edit the fixed joint transform.

Return type:

AssembledBodies

begin_assembly(

stage,

base_prim_path,

base_mount_path,

attachment_prim_path,

attachment_mount_path,

variant_set,

variant_name,

)

Start the robot assembly process.

Places the attachment robot relative to the base robot but does not compose them yet.

Parameters:

• stage (Usd.Stage) – USD stage for assembly

• base_prim_path (str) – Path to base robot prim

• base_mount_path (str) – Path to mount frame on base robot

• attachment_prim_path (str) – Path to attachment robot prim

• attachment_mount_path (str) – Path to mount frame on attachment robot

• variant_set (str) – Name of variant set to create/modify

• variant_name (str) – Name of variant to create

cancel_assembly()

Cancel the current assembly operation and reset state.

convert_prim_to_rigid_body(prim_path: str) → None

Convert a prim to a rigid body by applying the UsdPhysics.RigidBodyAPI Also sets physics:kinematicEnabled property to true to prevent falling from gravity without needing a fixed joint.

Parameters:

prim_path (str) – Path to prim to convert.

create_fixed_joint(

prim_path: str,

target0: str = None,

target1: str = None,

) → pxr.UsdPhysics.FixedJoint

Create a fixed joint between two bodies

Parameters:

• prim_path (str) – Prim path at which to place new fixed joint.

• target0 (str, optional) – Prim path of frame at which to attach fixed joint. Defaults to None.

• target1 (str, optional) – Prim path of frame at which to attach fixed joint. Defaults to None.

Returns:

A USD fixed joint

Return type:

UsdPhysics.FixedJoint

finish_assemble()

is_root_joint(prim) → bool

Check if a prim is a root joint (has no body0 or body1 target).

Parameters:

prim (Usd.Prim) – Prim to check

Returns:

True if prim is a root joint, False otherwise

Return type:

bool

mask_collisions(

prim_path_a: str,

prim_path_b: str,

) → pxr.Usd.Relationship

Mask collisions between two prims. All nested prims will also be included.

Parameters:

• prim_path_a (str) – Path to a prim

• prim_path_b (str) – Path to a prim

Returns:

A relationship filtering collisions between prim_path_a and prim_path_b

Return type:

Usd.Relationship

reset()

class AssembledRobot(

assembled_robots: AssembledBodies,

)

Bases: object

get_fixed_joint_transform()

Get the transform between mount frames in composed robot.

Returns:

translation with shape (3,) and orientation with shape (4,)

Return type:

Tuple[np.array, np.array]

set_fixed_joint_transform(

translation: array,

orientation: array,

)

Set the transform between mount frames in the composed robot.

Parameters:

• translation (np.array) – Local translation relative to mount frame on base robot.

• orientation (np.array) – Local quaternion orientation relative to mount frame on base robot.

property attach_path: str

Prim path of the floating (attach) body

Returns:

Prim path of the floating (attach) body

Return type:

str

property base_path: str

Prim path of the base body

Returns:

Prim path of the base body

Return type:

str

property collision_mask: pxr.Usd.Relationship

A Usd Relationship masking collisions between the two assembled robots

Returns:

A Usd Relationship masking collisions between the two assembled robots

Return type:

Usd.Relationship

property fixed_joint: pxr.UsdPhysics.FixedJoint

USD fixed joint linking base and floating body together

Returns:

USD fixed joint linking base and floating body together

Return type:

UsdPhysics.FixedJoint

property root_joints: List[pxr.UsdPhysics.Joint]

Root joints that tie the floating body to the USD stage. These are disabled in an assembled body, and will be re-enabled by the disassemble() function.

Returns:

Root joints that tie the floating body to the USD stage.

Return type:

List[UsdPhysics.Joint]

class AssembledBodies(

base_path: str,

attach_path: str,

fixed_joint: pxr.UsdPhysics.FixedJoint,

root_joints: List[pxr.UsdPhysics.Joint],

attach_body_articulation_root: pxr.Usd.Prim,

collision_mask=None,

)

Bases: object

Class representing two assembled rigid bodies connected by a fixed joint.

This class maintains references to the base and attach bodies, the fixed joint connecting them, and provides methods to manipulate their relative transform.

get_fixed_joint_transform() → Tuple[array, array]

Get the transform between mount frames in composed robot.

Returns:

translation with shape (3,) and orientation with shape (4,)

Return type:

Tuple[np.array, np.array]

set_fixed_joint_transform(

translation: array,

orientation: array,

)

Set the transform between mount frames in the composed body.

Parameters:

• translation (np.array) – Local translation relative to mount frame on base body.

• orientation (np.array) – Local quaternion orientation relative to mount frame on base body.

property attach_body_articulation_root: pxr.Usd.Prim

USD articulation root of the floating body

Returns:

USD articulation root of the floating body

Return type:

Usd.Prim

property attach_path: str

Prim path of the floating (attach) body

Returns:

Prim path of the floating (attach) body

Return type:

str

property base_path: str

Prim path of the base body

Returns:

Prim path of the base body

Return type:

str

property collision_mask: pxr.Usd.Relationship

A Usd Relationship masking collisions between the two assembled bodies

Returns:

A Usd Relationship masking collisions between the two assembled bodies

Return type:

Usd.Relationship

property fixed_joint: pxr.UsdPhysics.FixedJoint

USD fixed joint linking base and floating body together

Returns:

USD fixed joint linking base and floating body together

Return type:

UsdPhysics.FixedJoint

property root_joints: List[pxr.UsdPhysics.Joint]

Root joints that tie the floating body to the USD stage. These are disabled in an assembled body, and will be re-enabled by the disassemble() function.

Returns:

Root joints that tie the floating body to the USD stage.

Return type:

List[UsdPhysics.Joint]

Actions in isaacsim.robot_setup.assembler

ID	Display Name	Description
CreateUIExtension:Robot Assembler		Add Robot Assembler Extension to UI toolbar