Panda get started tutorial

[rickstaa]

This discussion post serves as a quick tutorial on working with the panda robot. For a more comprehensive guide, see the official panda documentation.

Setup instructions

For the instructions on setting up the Franka Control Interface on the workstation see the Franka documentation. If you have problems with building the real-time kernel see this issue on the Libfranka repository.

Control examples

Below you will find several control examples that get you familiar with how to work with the robot.

Control the robot using franka_ros

Let's first try controlling the robot with the examples given in the franka_ros documentation.

Libfranka and franka_ros build instructions

When installing the libfranka and franka_ros according to the panda documentation, make sure you build it from source. When building the franka_ros package you have to point catkin to the path where you compiled the libfranka library -DFranka_DIR:PATH=~/libfranka/build. Further, you have to make sure you provide the -DCMAKE_BUILD_TYPE=Release cmake argument.

Use the franka_gripper node to control the gripper

Start the franka_gripper node with the following command:

roslaunch franka_gripper franka_gripper.launch robot_ip:=172.16.0.2

We can then check the joint_states using:

rostopic echo /franka_gripper/joint_states

We can also call any of the spawned action services to control the robot. To see which action services are available, use the rostopic list command. All the topics which contain a /cancel, /feedback, /goal, /result and /status suffixes are action services. We can call these action services by publishing to the goal topic directly, using a python or C++ script or by using the actionlib axclient.py tool (see the docs). We can for example home the gripper using the following command:

 rostopic pub /franka_gripper/move/goal franka_gripper/MoveActionGoal "header:
  seq: 0
  stamp:
    secs: 0
    nsecs: 0
  frame_id: ''
goal_id:
  stamp:
    secs: 0
    nsecs: 0
  id: ''
goal:
  width: 0.04
  speed: 0.1"

The right message can be found by using bash tab autocompletion. Alternatively, we can use the axclient.py tool:

sudo apt install ros-noetic-actionlib-tools
rosrun actionlib_tools axclient.py /franka_gripper/move

Visualize the robot using the franka_visualization node

We can use the roslaunch franka_visualization franka_visualization.launch robot_ip:=172.16.0.2 load_gripper:=true command to show the robot state in rviz.

Control the robot using the franka_control_examples

Now let's try to control the whole robot using the franka_control package. For this, we can use any of the example launch files in the franka_example_controllers package. It contains the following examples:

• cartesian_pose_example_controller.launch: Performs a carteasian pose control sequence using the libfranka FrankaPoseCartesianInterface interface.
• cartesian_velocity_example_controller.launch: Performs a carteasian velocity control sequence using the libfranka FrankaVelocityCartesianInterface interface.
• elbow_example_controller.launch: Will move the elbow while keeping the gripper still.
• force_example_controller.launch: In this example, you can set the force the robot has to apply on a horizontal surface.
• cartesian_impedance_example_controller.launch: Will implement an impedance controller that makes the robot go back to a certain cartesian pose with a given stiffness.
• joint_position_example_controller.launch: Performs a join position control sequence using the libfranka PositionJointInterface interface.
• joint_velocity_example_controller.launch: Performs a join velocity control sequence using the libfranka VelocityJointInterface interface.
• model_example_controller.launch: Prints the full franka state using the libfranka FrankaStateInterface interface.

For more information on all the interfaces available in the libfranka library see the documentation. If you get an error during this examples you can reset the control using the following command:

rostopic pub -1 /franka_control/error_recovery/goal franka_msgs/ErrorRecoveryActionGoal "header:
  seq: 0
  stamp:
    secs: 0
    nsecs: 0
  frame_id: ''
goal_id:
  stamp:
    secs: 0
    nsecs: 0
  id: ''
goal: {}"

For several examples, the robot needs to start in the home position. The robot can be moved to this position with the move_to_start.launch launch file.

Example launch command

roslaunch franka_example_controllers move_to_start.launch robot_ip:=172.16.0.2 load_gripper:=true

Control the robot using moveit

We can also make use of Moveit to control the Franka robot through the franka_control package.
To test out Moveit control, after you build and sourced the catkin workspace, you can launch the example included in the panda_moveit_config using the following command:

roslaunch panda_moveit_config panda_control_moveit_rviz.launch load_gripper:=true robot_ip:=172.16.0.2

Additionally the real_panda_moveit_control contains a slightly modified version of this example:

roslaunch real_panda_moveit_control real_panda_moveit_control.launch