ROS Falcon Interface

This package provides a ROS interface for Novint Falcon haptic controller. This repository is developed based on the falcon library libnifalcon.

Dependencies

This repository has been developed and tested in Ubuntu 18.04 and ROS Melodic only. Other version may work but it is not guaranteed.

To use this package, you need to build and install libnifalcon.

git clone git@github.com:libnifalcon/libnifalcon.git
cd libnifalcon
mkdir build && cd build
cmake ..
make -j10
sudo make install

After installing libnifalcon, download and make this repository.

cd catkin_ws/src
git clone git@github.com:ZhuoyunZhong/ros_falcon_interface.git
cd ..
catkin_make

If you are not running as root, you might encounter the "firmware can not be found" error. According to libnifalcon, you will need to set up USB permissions to run its library.

cd ~/catkin_ws/src/ros_falcon_interface/linux
sudo cp 40-novint-falcon-udev.rules /etc/udev/rules.d/
sudo udevadm control --reload-rules
sudo udevadm trigger

Unplug and re-plug your device and try

findfalcons

It should be able to find the falcon now.

Running

• Connect the Novint Falcon device with the computer

• Run this interface by

  rosrun ros_falcon_interface ros_falcon_interface
  

  You may need to calibrate your device, please follow the instruction. The robot should be able to home itself at (0.0, 0.0, 0.125), which is considered to be the center point of its workspace.

Interface Details

The following ROS topics and methods are provided to interact with the Novint Falcon. Please be careful when setting up force feedback or position goal. Falcon may have strong reaction due to its controller design.

1. The position of the device is sent to topic "falcon_pos".

   rostopic echo /falcon_pos
   

   Data type is geometry_msgs::Point.

2. The button messages of the device are sent to topic "falcon_button".

   rostopic echo /falcon_button
   

   Data type is std_msgs::Int8. When the button is pressed and released, one topic message would be sent out. 1, 2, 3 and 4 represent center, forward, left and right button.

   ---

3. The LED light color could be changed by publishing std_msgs/String data to "set_falcon_led". Example:

   rostopic pub /set_falcon_led std_msgs/String "data: 'r'"
   

   Three colors, 'red' / 'r', 'green' / 'r', 'blue' / 'b' can be set up. When the input is not these three, the combined RGB color would be displayed, which is also the default color.

4. There are four different haptic mode for haptic device. They can be changed by publishing std_msgs/Int8 data to "set_falcon_led". Example:

   rostopic pub /set_falcon_haptic_mode std_msgs/Int8 "data: 0"
   

   0, the default mode, represents self-centering mode. In this mode, falcon will always home itself in the center point. 1 is position keeping mode. This mode is activated when one tries to set up a goal point and let falcon to follow. 2 is constant force mode, which is activated when one sends a constant force feedback. All the other input will lead to the final mode, no haptic force mode.

   Position keeping and constant force modes are explained in details below.

5. To have falcon provide a haptic force. Send geometry_msgs/Vector3 data to "set_falcon_force". Example:

   rostopic pub /set_falcon_force geometry_msgs/Vector3 "x: 1.5
   y: 1.5
   z: 1.0"
   

   The haptic mode will be set to constant force mode.

6. To set a goal location for falcon to go. Send geometry_msgs::Point data to "set_falcon_point". Example:

   rostopic pub /set_falcon_point geometry_msgs/Point "x: -0.02
   y: 0.02
   z: 0.15"
   

   A PID controller is implemented and tuned in order to let falcon to reach the desired goal. The haptic mode will be set to position keeping mode. The approximate valid range for 3 axes are -0.06 < x < 0.06, -0.06 < y < 0.06 and 0.075 < z < 0.175.

For more potential usages of the interface and driver for Novint Falcon, please also check the examples provided by libnifalcon.