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name: chain-kinematics description: "Use for direct IKPy Chain and Link construction, NumPy forward or inverse kinematics, masks, bounds, orientations, DH/URDFLink modeling, serialization, concatenation, and numerical validation." disable-model-invocation: true metadata: disco-role: operating license: Apache 2.0

Chain kinematics

Use this route when a user needs to build or manipulate an IKPy Chain, compute forward kinematics, solve a position/orientation inverse-kinematics target, or validate a result numerically.

Route by task

• Novice: read workflows.md first for the tiny OriginLink + URDFLink fixture, full joint-vector convention, FK/IK recipes, and a validation loop.
• Expert: read api-reference.md for exact v4.0.0 signatures, shapes, DH/URDF conventions, optimizer arguments, masks, and serialization constraints. Use troubleshooting.md when a solver, bound, orientation, or input-shape check fails.
• Run the safe deterministic helper scripts/smoke_chain.py after installation; it exercises construction, FK, masks, IK, bounds, orientation, DH, prismatic links, and geometry shapes without loading a robot file.

Scope and handoffs

This route owns direct Chain, Link, OriginLink, URDFLink, and DHLink construction; NumPy FK/IK; full versus active joint vectors; bounds and orientation targets; chain conversion/concatenation; JSON serialization contracts; and residual-based numerical checks.

• Keep every joint value, including inactive links and the terminal link, in a full vector. The terminal link should be fixed and inactive; verify the mask explicitly because this release's constructor check is implementation- brittle.
• Route URDF/MJCF file parsing, model-tree discovery, and parser-specific selection to robot-model-import.
• Route backend="jax" and JAX-specific optimizer behavior to jax-backend.
• Route plotting and geometry visualization implementation to visualization-geometry.