ik_ros

Inverse kinematics integration for ROS. This package provides a standardized interface for IK solvers and ROS.

NOTE: this package is apart of a wider framework that is planned to be made publicly available in the near future. As such, the examples will not currently work.

System overview

The figure above shows an overview for ik_ros. Two nodes are provided (green) that setup the problem, and solve the problem. A setup node collects the required data and packs the problem parameters in a ROS message. The message is passed to the solver node at a given sampling frequency. Finally, the solver node takes the problem and passes it to an IK solver. The solution is then published to ROS. Note, both a ik_ros/IKSolution and sensor_msgs/JointState message are published after each solve. In addition, the solver node includes a service for solving IK problems that takes a problem as input and response with the joint state target solution. Several interfaces are already supported for common solvers (see below). The package has been designed to be extensible so additional solvers or custom IK solver interfaces can be easily added by implementing an interface and solver node - see the next section for details.

Adding a new interface

To add a new interface you need to implement the following:

1. Add an IK problem message to ik_ros/msg (remember to include in ik_ros/CMakeLists.txt)
   • this must contain a header, i.e. add the line std_msgs/Header header
   • this file should contain the relevant problem parameters
   • typically this is variables that change at solve time
   • do not include solver initialization variables here, these should be parameters set in the IK solver node
2. Add a directory to ik_ros/src/ik_ros with the name of the interface.
3. In the new directory implement the following files
   • __init__.py, an empty file for packaging
   • setup_node.py, implement a class that inherits from the IKSetupNode in ik_ros/src/ik_ros/ik_setup_node.py. The goal of this class is to setup the relevant subscribers and tf listeners to pack the IK problem. Note, there are abstract methods that must be implemented that come from the IKSetupNode class. Also note, you must call post_init at the end of the __init__ method.
   • interface.py, implement a class that inherits from the IK in ik_ros/src/ik_ros/ik_interface.py. The goal of this class is to provide the interface for the IK solver. Note, this is not a ROS node, but will be instantiated within a ROS node so rospy functionality is available to use (e.g. rospy.get_param). Also, there are abstract methods that must be implement that come from the IK parent class.
4. Add your interface to the solver_interfaces variable in ik_ros/src/ik_ros/ik_solver_interfaces.py.

Supported interfaces

• trac_ik
• EXOTica
• RBDL (in development)
• pybullet
  • Note, this uses the ROS-Pybullet Interface