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gazebosim / gazebo-classic

Gazebo classic. For the latest version, see https://github.com/gazebosim/gz-sim
http://classic.gazebosim.org/
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Update GearBox Joint Definition #1058

Open osrf-migration opened 10 years ago

osrf-migration commented 10 years ago

Original report (archived issue) by John Hsu (Bitbucket: hsu, GitHub: hsu).

Current model definition for gearbox joint is not flexible enough.

We should switch from needing parent link, child link, reference link, axis1 and axis2 to specifying 2 single dof revolute/prismatic joints.

Inspired by trying to model pr2 like 4-joint parallel gripper.

osrf-migration commented 10 years ago

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

osrf-migration commented 10 years ago

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

osrf-migration commented 10 years ago

Original comment by Dave Coleman (Bitbucket: Dave Coleman).

Will this support the URDF mimic tag for all robots automatically (without need of additional elements)?

osrf-migration commented 10 years ago

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

@davetcoleman Not yet, current definition has a limitation that the two joints constrained by a gearbox constraint must share a common body. Because of timing, getting ready for 3.0 release, I don't have time to generalize gearbox in a way that one can constrain any pairs of joints with a mimic tag yet. Will look into this after the 3.0 release.

Please vote on this issue if this is a useful feature. Thanks.

osrf-migration commented 9 years ago

Original comment by Stefan Kohlbrecher (Bitbucket: Stefan_Kohlbrecher).

We have a hand model that has a mimic tag and I just ran into a similar issue as described here on Gazebo Q/A, namely the hand violently shaking as soon as grasping an object is attempted (using Gazebo2). Are mimic joints supposed to be supported in Gazebo now, or are issues with them expected? The conversation in this ticket sounds like the mimicimplementation was never finished.

osrf-migration commented 8 years ago

Original comment by Anonymous.

+1 for interest in 'mimic' support, where did this feature land?

osrf-migration commented 8 years ago

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

osrf-migration commented 7 years ago

Original comment by Hamza Merzić (Bitbucket: hamzaethz).

+1. Any patches/workarounds for this one yet?

osrf-migration commented 7 years ago

Original comment by Hamza Merzić (Bitbucket: hamzaethz).

Any pointers on how to properly implement joint mimicking for any of the physics solvers would be much appreciated. If it works out, I would love to try to generalize it and contribute back. Thanks!

wakoko79 commented 2 years ago

Can anyone clarify how the current gearbox model works? The explanation is not very helpful, and there are no tutorials on the gearbox joint. link

Parameter for gearbox joints. Gearbox ratio is enforced over two joint angles. First joint angle (theta_1) is the angle from the gearbox_reference_body to the parent link in the direction of the axis element and the second joint angle (theta_2) is the angle from the gearbox_reference_body to the child link in the direction of the axis2 element.

What does angle from the gearbox_reference_body to the parent link in the direction of the axis element supposed to mean? How can you measure a 2D angle between 2 bodies without specifying a plane of reference (or axis of rotation)?

I can't understand how to properly put values on <axis>and <axis2>. In relation to the two revolute joints connected by this joint, what axis should I put? Sometimes the mechanism just stops or the model just goes wild if I put wrong values on it.

Please someone explain this, as I've searched google for 2 weeks now to no end.