A simple demo that uses a URDF to describe a marionette, trep to integrate the dynamics of the marionette, and various interfaces to allow a user to control the system.
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README.md

trep_puppet_demo

This ROS package is a demo uses trep to integrate the dynamics of a humanoid puppet while a user is directly controlling string endpoints through various interfaces. A URDF of the puppet as well as stl files for each of the joints is used in conjunction with the robot state publisher and rviz to animate the simulation.

Simulation breakage

In the trep simulation of the puppet's dynamics, there are several important things to note. The strings are implemented as constraints between the endpoints and the attachment points on the model. As such, it is quite easy for the user to move the endpoints to a geometrically infeasible configuration e.g. there is no set of puppet joint configurations that allow the constraints to be satisfied. In this case warnings saying No solution to DEL equations! are printed, and the simulation is automatically reset. As the number of constraints goes up, for example, through the addition of leg strings, these infeasible configurations become easier and easier to find.

Another note is that the strings are currently more accurately thought of as rods. They are fixed length, and actually able to support compressive forces. This may be changed in the future.

Interfaces

A description of the interfaces implemented thus far is presented below.

Direct joint control

In this mode, there are no dynamics, and the user has the ability to directly control each of the puppet's joints via the joint_state_publisher GUI. Access with puppet_vis.launch launch file.

Interactive markers

Use interactive markers to control the string endpoints in rviz via the [interactive_markers] ROS package. Access with the puppet_sim.launch launch file.

Skeleton tracking

This mode uses an OpenNI compatible device along with the NITE skeleton tracking libraries to allow a user to control the string endpoints via their own hands, shoulders, knees, etc. This mode requires the openni_launch ROS package, as well as the skeletontracker_nu and skeltonmsgs_nu packages. These packages are very similar to the openni_tracker package, but instead of just sending /tf information, they also publish topics with custom messages containing all of the transforms for each user being tracked. Access this mode via the puppet_skeleton_control.launch launch file.

Launch file options

gui (bool, default:false)

  • specify whether or not to start up the joint_state_publisher GUI. This is really only useful in the puppet_vis.launch launch file.

vis (bool, default:false)

  • if true, start rviz with a nice configuration for the current mode

legs (bool, default:false)

  • if true, connect strings to the legs

shoulders (bool, default:false)

  • if true, connect two independent strings to the shoulders rather than two strings going to a single control point

path_len (int, default:60)

  • in the skeleton tracking interface paths are rendered to show the path that the control has followed, this integer controls how many points should be in that path

kinect (bool, default:true)

  • if true, try and run openni.launch when running the skeleton interface mode; may be useful for debugging

License

Copyright (C) 2013 Jarvis Schultz, schultzjarvis@gmail.com

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.