franka_interactive_controllers

Control interface built on top of franka_ros that allows to control the franka robot arm in several joint and Cartesian space impedance control schemes for interactive, safe and reactive (mostly DS-based) motion planning and learning. This low-level control interface is used and developed by/for Prof. Nadia Figueroa and her collaborators and students. Initially developed at MIT in the Interactive Robotics Group continued development at the University of Pennsylvania.

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Installation

Besides franka_ros and by consequence libfranka this package depends on several other code repositories that are robot-agnostic and useful for control and learning of motion policies from demonstrations.

To install this repo and all its dependencies do the following steps:

• In your catkin src directory clone the repository

$ git clone https://github.com/nbfigueroa/franka_interactive_controllers.git

• wstool gets all other git repository dependencies, after the following steps you should see extra catkin packages in your src directory.

$  wstool init
$  wstool merge franka_interactive_controllers/dependencies.rosinstall 
$  wstool up 

• Query and installs all libraries and packages

$ rosdep install --from-paths . --ignore-src --rosdistro <your-ros-distro> 

• Install some additional python dependencies

$ sudo apt install python3-psutil python3-tkinter

• Finally complie

  $ cd ~/catkin_ws
  $ catkin_make
  $ source devel/setup.bash
  $ catkin_make
  $ rospack profile

You might need to source the ./bashrc file and compile again if the first compliation could not find some of the in-house dependencies. If roscd doesn't find the compiled packages run rospack profile.

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Instructions

We include a list of instructions for using the franka panda arm with this controller package:

• Startup the robot
• External tool compensation (necessary if your experiment requires mounting a tool/accesory on the franka hand)
• Basic robot operating functionalities (open/close gripper and move robot to a desired joint position bypassing franka_ros -- useful to startup an experiment).
• Kinesthetic Teaching + Data Collection and Pre-Processing
• Learning DS motion policies
• Executing DS motion policies
• Executing custom motion policies (MPC, feed-forward NN, DMP, etc)

Usage

Following we detail instructions on how to bringup the controllers and their functionalities:

Main Robot Launch

To bring up the standalone robot with franka_ros without any specific controller (useful for testing -- can be included in your custom launch file):

roslaunch franka_interactive_controllers franka_interactive_bringup.launch 

This will load all franka_ros (franka_control, franka_gripper, etc.) functionalities + gripper GUI controller + configured rviz settings.

Robot Controllers

Joint Gravity Compensation

To load the joint gravity compensation controller launch the following:

roslaunch franka_interactive_controllers joint_gravity_compensation_controller.launch

• This will load a joint gravity compensation torque controller. It compensates (from code) the weight of any additional tool (i.e., a tool grasped by the hand or cameras mounted on the gripper). As well as the capability to lock certain joints for ease of demonstration.
• The external forces imposed on the end-effector with the additional weight should be defined in ./config/external_tool_compensation.yaml. Instructions on how to finding values for your custom tool here. You can toggle to activate/deactivate this compensation online using dynamic reconfigure. Default is set to true.
• The desired joints to lock and the locked positions can be modified online by dynamic reconfigure. Default is set to false for all locks.
• To launch franka_interactive_bringup.launch within this same launch file set load_franka_control:=true. Default is set to false.

NOTE: If you run this script and the robot moves by itself, that means that your external_tool_compensation forces are incorrect. See external_tool_compensation instructions to correct it.

Kinesthetic Teaching/Recording Pipeline

You can launch the joint gravity compensation controller together with data recording nodes from my easy-kinesthetic-teaching repository latest-franka branch.

roslaunch franka_interactive_controllers franka_kinesthetic_teaching.launch

If you installed and compiled everything correctly you should see the following windows on your screen:

This will run scripts and nodes that will allow you to:

• Select topics to record and define path to save rosbags.
• Run all functionalities from joint gravity compensation controller.
• Bringup rosservice to record/stop a recording.
• Visualize end-effector trajectories being recorded in real-time and gripper state (open/closed).
• Replay recorded end-effector trajectoriers and gripper state in RViz, franka controllers and launch files must be turned off for this functionality.

See Kinesthetic Teaching/Recording instructions for definitions and usage.

Cartesian Impedance Controller with Pose Command

To load a cartesian impedance controller with pose command (a PD control law with position error tracking; i.e., stiffness control and velocity damping) launch the following:

roslaunch franka_interactive_controllers cartesian_pose_impedance_controller.launch

This launch file will load a cartesian impedance controller that:

• Takes as input a desired end-effector pose (position and orientation) as a geometry_msg::PoseStamped with topic name /cartesian_impedance_controller/desired_pose.
• Will compensate for external forces imposed by additional tools/accesories mounted on the gripper (as described in joint gravity compensation controller above).
• Control for a desired nullspace configuration, defined in config/impedance_control_additional_params.yaml, stiffness for nullspace control can be modified online by dynamic reconfigure.

Cartesian Impedance Controller with Twist Command

To load a cartesian impedance controller with twist command (a PD control law with position and velocity error tracking) launch the following:

roslaunch franka_interactive_controllers cartesian_twist_impedance_controller.launch

This launch file will load a cartesian impedance controller that:

• Takes as input a desired end-effector twist (linear and angular velocity) as a geometry_msg::Twist with topic name /cartesian_impedance_controller/desired_twist.
• Will compensate for external forces imposed by additional tools/accesories mounted on the gripper (as described in joint gravity compensation controller above).
• Control for a desired nullspace configuration, defined in config/impedance_control_additional_params.yaml, stiffness for nullspace control can be modified online by dynamic reconfigure.

DS-based Passive Cartesian Impedance Controller

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Joint Impedance Control with Position Command

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Joint Impedance Control with Velocity Command

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Contact

Maintainer: Nadia Figueroa (nadiafig @ seas dot upenn edu)
Code Contributions by: Bilkit Githinji, Shen Li.

Licenses

Please note that the code for some of the controllers in this repository is derived from franka_ros, specifically the franka_example_controllers package which is licenced under Apache 2.0. The remaining code in the repository is licensed under an MIT license (see LICENSE for details).