#Checks reference

The codes below appear in the Checks tab. The first letter says what kind of problem it is:

R — robot structure (the link tree)
P — physical properties (mass, inertia, limits)
A — assets (mesh files and packages)
S — xacro style

For how to use the Checks tab, see Find and fix problems.

#Structure

Code	Severity	Found when	How to fix
`R-001`	Error	There is no root link, or several unconnected trees each have children	Connect every link to one tree with joints
`R-002`	Error	Following joints from parent to child comes back to the same link	Remove or redirect the joint that closes the loop
`R-003`	Error	A joint's `parent` or `child` names a link that doesn't exist	Fix the typo, or declare the missing link
`R-004`	Error	Two links, or two joints, have the same name	Rename one; in xacro, check that prefixes are applied
`R-005`	Error	A `<mimic>` names a joint that doesn't exist, or mimics form a loop	Point the mimic at an existing, non-mimic joint

#Physical properties

Code	Severity	Found when	How to fix
`P-001`	Warning	A link has no `<inertial>`	Add mass and inertia. Fine to ignore for pure frames like `tool0`. Not checked for MuJoCo models, which compute inertia from geoms
`P-002`	Warning	The inertia values are physically impossible (the tensor is not positive-definite)	Recompute the inertia, for example from the CAD model. Check `ixx`, `iyy`, `izz` are positive and each is less than the sum of the other two
`P-003`	Error / Warning	Mass is negative (error), zero or missing (warning), or over 10,000 kg (warning — usually grams used by mistake)	Give every real part its mass in kilograms
`P-004`	Warning	A revolute or prismatic joint has no lower or upper limit	Add `<limit lower upper effort velocity>`
`P-005`	Warning	A continuous joint declares `lower` / `upper`	Remove them (they're ignored), or make the joint revolute
`P-006`	Warning	A joint's `effort` or `velocity` limit is zero	Set the real values; controllers may refuse to move the joint otherwise

#Assets

Code	Severity	Found when	How to fix
`A-001`	Error	A mesh file can't be found, a `package://` path names a package that isn't in the opened folder, or has no package name	See Meshes are missing
`A-002`	Warning	A package has no `package.xml` in the opened folder, but its meshes were found by looking in parent folders	Open the folder that contains `package.xml`
`A-003`	Info	Some meshes are scaled by 0.001 or 1000 and others aren't — a sign of mixed millimetres and metres	Check each mesh's units; URDF uses metres

#Xacro style

These only apply to .xacro files.

Code	Severity	Found when	How to fix
`S-001`	Info	`$(arg name)` is used without a matching `<xacro:arg>`	Declare the argument with a default
`S-002`	Info	A `<xacro:property>` or `<xacro:arg>` is declared but never used	Remove it, or check for a typo where it should be used
`S-003`	Info	A `<xacro:macro>` is declared but never called	Remove it, or call it
`S-004`	Warning	An expression divides by zero	Fix the expression or the property it uses
`S-005`	Info	A link or joint name isn't `snake_case`	Off by default

#Loading problems

Some problems stop the model from loading properly. They are listed together under Loading problems in the Checks tab, also pop up as a message in the corner of the window, and appear in the Problems panel in VS Code:

Message is about	Meaning
XML that can't be parsed	The file isn't valid XML — often an unclosed tag or a stray `&`. Nothing can be shown until it's fixed
Xacro that can't be expanded	An include, macro call or argument failed. The message names it
An include cycle	Two xacro files include each other (or a file includes itself)
A macro that calls itself too deeply	A recursive macro has no stopping condition (limit: 200 levels)
A file that isn't valid XML	The robot file or an included file is empty or not XML
A skipped xacro expression	One `${…}` expression failed; the rest of the file was expanded without it
`$(find pkg)` for an unknown package	The package isn't in the opened folder or package roots
A link with more than one parent	Two joints name the same `child`
`lower` greater than `upper`	A joint's limits are reversed
SRDF or semantic files	A configured SRDF or YAML file couldn't be read or parsed

#Quick fixes

Check	Fix
`P-001`	Inserts a small default `<inertial>`
`P-003`	Sets the mass to 1.0
`P-004`	Inserts a default `<limit>`
`P-005`	Removes the limits from the continuous joint
`P-006`	Sets effort to 100 and velocity to 1.0

The inserted values are placeholders. Replace them with real numbers.

#Health score

Model health = 100 − 10 × errors − 3 × warnings − 0.5 × infos, never below zero.