Implementation:Haosulab ManiSkill ArticulationJoint

Knowledge Sources	Haosulab_ManiSkill
Domains	Robotics, Simulation, Articulated Bodies
Last Updated	2026-02-15 08:00 GMT

Overview

Concrete tool for managing batched articulation joints across parallel simulation environments.

Description

The ArticulationJoint dataclass wraps physx.PhysxArticulationJoint objects, providing a batched interface for querying and configuring joint properties. All joints of the same type across parallel sub-scenes are restricted to having the same properties.

Key attributes:

index -- Index of this joint among all joints in the articulation.
active_index -- Index among active (actuated) joints only.
articulation -- Reference to the parent Articulation (None for merged views).
child_link / parent_link -- References to the connected Link objects.

Key properties and methods:

type -- Joint type string ("revolute", "prismatic", "fixed", etc.).
damping / friction / stiffness -- Joint dynamic properties.
limits -- Joint position limits as a tensor of shape (N, 1, 2).
set_drive_properties() -- Configure PD drive stiffness, damping, force limit, and mode.
set_limits() -- Set joint position limits (before GPU init only).

The class factory method create() constructs the joint wrapper from raw physx joint objects and articulation references.

Usage

ArticulationJoint objects are accessed through their parent Articulation's joints, active_joints, or corresponding map attributes. They are used to configure robot joint controllers and query joint properties.

Code Reference

Source Location

Repository: Haosulab_ManiSkill
File: mani_skill/utils/structs/articulation_joint.py

Signature

@dataclass
class ArticulationJoint(BaseStruct[physx.PhysxArticulationJoint]):
    index: torch.Tensor
    active_index: torch.Tensor
    articulation: Optional[Articulation] = None
    child_link: Optional[Link] = None
    parent_link: Optional[Link] = None
    name: str = None

    @classmethod
    def create(
        cls,
        physx_joints: list[physx.PhysxArticulationJoint],
        physx_articulations: list[physx.PhysxArticulation],
        scene: ManiSkillScene,
        scene_idxs: torch.Tensor,
        joint_index: torch.Tensor,
        active_joint_index: torch.Tensor = None,
    ) -> "ArticulationJoint": ...

    def set_drive_properties(
        self, stiffness: float, damping: float, force_limit: float = ..., mode: str = "force"
    ) -> None: ...

Import

from mani_skill.utils.structs.articulation_joint import ArticulationJoint

I/O Contract

Inputs

Name	Type	Required	Description
physx_joints	list[PhysxArticulationJoint]	Yes	Raw physx joint objects
physx_articulations	list[PhysxArticulation]	Yes	Parent articulation objects
joint_index	torch.Tensor	Yes	Index of this joint among all joints
active_joint_index	torch.Tensor	No	Index among active joints (None if fixed)

Outputs

Name	Type	Description
type	str	Joint type string ("revolute", "prismatic", "fixed", etc.)
limits	torch.Tensor	Joint limits of shape (N, 1, 2) with [low, high]
damping	float	Joint damping coefficient

Usage Examples

Basic Usage

# Access joints from an articulation
robot = env.agent.robot
for joint in robot.active_joints:
    print(f"{joint.name}: type={joint.type}, limits={joint.limits}")

# Configure drive properties for a specific joint
joint = robot.active_joints_map["joint_1"]
joint.set_drive_properties(stiffness=1000, damping=100, force_limit=100, mode="force")

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Principle

Implementation

Heuristic

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