snake_ws

ROS workspace with packages for simulated control of the CMU Biorobotics Lab's SEA snake and SEA hexapod (aka snake monster).

Tested with ROS Kinetic and Ubuntu 16.04

Special thanks to the HEBI Robotics team for providing the meshes and URDF files for their modular SEA actuators. Howie Choset's Biorobotics lab (CMU) used these actutors to construct modular snake and heaxapod robots. This project builds on HEBI's mesh and URDF files to develop dynamic simulations of each robot to enable testing and experimentation, e.g., of different controllers, in Gazebo. The project implements several example controllers including a CPG-based walking controller for the SEA hexapod, and a serpenoid gait controller for the snake.

Necessary Packages

Python SciPy:

$ sudo apt-get install python-scipy

Gazebo Effort Controllers:

$ sudo apt-get install ros-kinetic-effort-controllers

Build and source the workspace

Source ROS if this is not already handled:

$ source /opt/ros/kinetic/setup.bash

Move to the downloaded workspace, build, and source:

$ cd snake_ws
$ catkin_make
$ source devel/setup.bash

Run example controllers in Gazebo

SEA snake

Make the gaits.py script executable:

$ roscd snake_control/scripts/
$ sudo chmod +x gaits.py

Launch the gazebo simulator, ROS control interfaces, and execute gait control script:

$ roslaunch snake_control gazebo.launch gait:=true paused:=false

If the commands are successful, gaits.py should send joint commands that cause the snake robot simulation in gazebo to start sidewinding. The python file publishes desired joint angles and ROS control is used to implement a PD controller to drive the dynamic robot model in tracking these angles.

SEA hexapod

Launch the gazebo simulator and ROS control interfaces:

$ roslaunch snake_monster_control gaz_control.launch

Open a seperate terminal and execute a control script:

$ cd snake_ws/src/snake_monster_control/scripts
$ python walking_controller.py

If the commands are successful, walking_controller.py should send joint commands that cause the hexapod robot simulation in gazebo to start walking. The python file publishes desired joint angles and ROS control is used to implement a PD controller to drive the dynamic robot model in tracking these angles.

Acknowledgements

The snake_control and snake_monster_control packages were originally developed and maintained by Alex Ansari while working in Prof. Howie Choset's Biorobotics Lab at Carnegie Mellon University. (The workspace uses model files from HEBI Robotics and redistributes the gazebo_ros_control package so the workspace is self-contained.) You are free to use this code subject to the licensing agreements in each package. If you do use these packages, please cite and ackowledge source materials.

Contributing

This project is intended to be a simple example and starting point for students to perform simulated control of the robots in CMU's Biorobotics Lab. If you make changes/improvements, please consider contributing these back to this open-source project so that others may benefit!