GraspJoint Plugin

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GraspJoint Plugin (GraspJoint)

See GraspJoint/README.md as well.

This is a plugin for Ignitions that generates a joint dynamically during simulation with a topic where you send a string that contains parent model, parent link, child model and child link. It can be used to grab things in gazebo and for modular robots.

It will move the object to the link with an offset and then add a DetachableJoint so the objects stays in that position relative to the parent joint.

1. Include the plugin in the .sdf world.

It does not need to be inside a model.

<plugin
    filename="GraspPlugin"
    name="grasp_plugin::GraspJoint">
    <attachtopic>/grasp/attach</attachtopic>
    <offset_x>1.0</offset_x>
    <offset_y>0.0</offset_y>
    <offset_z>1.5</offset_z>
    </plugin>

The offsets are in meters offset in the world frame. TODO: change this to parent link frame.

2. Create and Destroy the Link Dinamically

To create a link you have to send a ignition::msgs::StringMsg with this architecture: [ParentModel][ParentLink][ChildModel][ChildLink][attach]

If you want to detach use [detach]

like this:

ign topic -t /AttachableJoint -m ignition.msgs.StringMsg -p 'data:"[parentModel][ParentLink][ChildModel][ChildLink][attach]"'

You can send it from ROS2, see https://github.com/ignitionrobotics/ros_ign/tree/melodic/ros_ign_bridge

Use a link that has a body, not an empty link, otherwise it somehow doesn't work.

In world/diff_drive.sdf: use

ros2 topic pub /box2/attach std_msgs/msg/String 'data: "[diff_drive][lidar_link][box2][box_body][attach]"' --once  

Installation

1. Clone this repository e.g.

git clone https://github.com/kas-lab/Ign-gazebo-AttachablePlugin.git

2. Build your workspace using colcon