Make joint axis reference frame relative to child

[osrf-migration]

Original report (archived issue) by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

In the sdf documentation, the element is listed as using the joint frame, when in practice it uses the model frame (see Joint.cc:175-191).

I recommend fixing the code to match what the documentation currently says, rather than just changing the documentation, since it will simplify model creation to fix this.

We should test the PR2, Atlas, Polaris, and other models to ensure that fixing this bug does not break things.

[osrf-migration]

Original comment by felix-kolbe (Bitbucket: felix-kolbe).

---

Confirming, voting for code fix.

We're just trying to describe our robot with SDF 1.3 and found that awkward behavior. E.g. we want to revolve around the z axis of a link frame we tilted but have to define the corresponding model axis (y in this case) as the joint axis. That way it works but is confusing nonsense.

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

See pull request #442, which changes the documentation. Changing the underlying code will take more work.

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

See also pull request #461, which clarifies that joint axis is specified in model frame of parent.

[osrf-migration]

Original comment by John Hsu (Bitbucket: hsu, GitHub: hsu).

---

• changed priority from "major" to "critical"

upgrading this to critical, as the current interpretation is non-ideal. Exactly how to make the change and changing code without breaking existing user code might take some time to tic-toc.

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

• changed state from "new" to "on hold"

after VRC

[osrf-migration]

Original comment by Ian Chen (Bitbucket: Ian Chen, GitHub: iche033).

---

• changed state from "on hold" to "open"

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

• changed title from "Joint axis reference frame doesn't match documentation" to "Make joint axis reference frame relative to child"

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

• set component to "physics"

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

I've started a branch in sdformat to address this issue.

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

• set assignee_account_id to "557058:5de38267-b118-494c-aa76-4fab35448816"
• set assignee to "scpeters (Bitbucket: scpeters, GitHub: scpeters)"

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

pull request #963

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

---

• changed state from "open" to "resolved"

pull request #963

[osrf-migration]

Original comment by Nate Koenig (Bitbucket: Nathan Koenig).

---

• set version to "all"

[osrf-migration]

Original comment by Nate Koenig (Bitbucket: Nathan Koenig).

---

• changed state from "resolved" to "closed"