Joystick Control

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This package can be used to control the movements of any rover in the Interbotix X-Series LoCoBot Family using a SONY PS3 or PS4 controller via Bluetooth. In this demo, the 'arm' (if equipped) and 'pan/tilt' servos work in 'position' control mode, the gripper operates in 'PWM' mode, and the base operates in 'velocity' control mode. Refer to the joystick button map below to see how to operate the robot. Specifically, some of the joystick controls manipulate individual joints while others are used to perform 'inverse kinematics' on all the joints to get the end-effector of the robot (defined at 'ee_gripper_link') to move as if it's in Cartesian space. This is done using the modern_robotics code library offered by Northwestern University.



As shown above, the interbotix_xslocobot_joy package builds on top of the interbotix_xslocobot_control package. To get familiar with the nodes in the interbotix_xslocobot_control package, please look at its README. The other nodes are described below:

  • joy - a ROS driver for a generic Linux joystick; it reads data from a SONY PS3 or PS4 controller joystick over Bluetooth and publishes sensor_msgs/Joy messages to the /<robot_name>/commands/joy_raw topic
  • xslocobot_joy - responsible for reading in raw sensor_msgs/Joy messages from the /<robot_name>/commands/joy_raw topic and converting them into LocobotJoy messages; this makes the code more readable and allows users to remap buttons very easily later. The new messages are then published on the /<robot_name>/commands/joy_processed topic.
  • xslocobot_robot - responsible for reading in LocobotJoy messages from the /<robot_name>/commands/joy_processed topic and publishing joint, gripper, and pan/tilt commands to the xs_sdk node; while the 'waist' joint is directly controlled via the PS3/PS4 joystick, other buttons allow position-ik to be performed using all the arm joints. It also publishes velocity commands to the mobile base.


After pairing your Bluetooth joystick controller using the Pairing Your Controller Guide, type the following in a terminal (let's say to control the locobot_wx200 robot with no lidar):

$ ros2 launch interbotix_xslocobot_joy robot_model:=locobot_wx200

A red error message might appear in the screen saying Couldn't open joystick force feedback!. This is normal and will not affect the joystick operation. To further customize the launch file at run-time, look at the table below:

Argument Description Default Choices
robot_model model type of the Interbotix LoCoBot such as locobot_base or locobot_wx250s.   locobot_base, locobot_px100, locobot_wx200, locobot_wx250s
robot_name name of the robot (could be anything but defaults to locobot). locobot  
arm_model the Interbotix Arm model on the LoCoBot; this should never be set manually but rather left to its default value. PythonExpr('"mobile_" + "' + LaunchConfig(robot_model) + '".split("_")[1]')  
use_rviz launches RViz if set to true. true true, false
rviz_frame fixed frame in RViz; this should be changed to map or odom if mapping or using local odometry respectively; base_footprint otherwise. LaunchConfig(robot_name) + '/base_footprint'  
use_base if true, the base ROS nodes are launched. true true, false
use_lidar if true, the RPLidar node is launched. false true, false
use_camera if true, the RealSense camera nodes are launched. false true, false
mode_configs the file path to the 'mode config' YAML file. PythonExpr('"' + LocalVar('FindPackageShare(pkg= interbotix_xslocobot_joy) + 'config' + 'modes_base.yaml'') + '" if "' + LaunchConfig(robot_model) + '" == "locobot_base" else "' + LocalVar('FindPackageShare(pkg= interbotix_xslocobot_joy) + 'config' + 'modes_all.yaml'') + '"')  
threshold value from 0 to 1 defining joystick sensitivity; a larger number means the joystick should be less sensitive. '0.75'  
controller type of controller. ps4 ps4, ps3
launch_driver true if xslocobot_control should be launched - set to false if you would like to run your own version of this file separately. true true, false
xs_driver_logging_level set the logging level of the X-Series Driver. INFO DEBUG, INFO, WARN, ERROR, FATAL
use_sim if true, the DYNAMIXEL simulator node is run; use RViz to visualize the robot's motion; if false, the real DYNAMIXEL driver node is run. false true, false
base_type the base type of the LoCoBot. EnvVar(INTERBOTIX_XSLOCOBOT_BASE_TYPE) kobuki, create3
use_gripper if true, the default gripper is included in the robot_description; if false, it is left out; set to false if not using the default gripper. true true, false
show_ar_tag if true, the AR tag mount is included in the robot_description; if false, it is left out; set to true if using the AR tag mount in your project. true true, false
show_gripper_bar if true, the gripper_bar link is included in the robot_description; if false, the gripper_bar and finger links are not loaded. Set to false if you have a custom gripper attachment. true true, false
show_gripper_fingers if true, the gripper fingers are included in the robot_description; if false, the gripper finger links are not loaded. Set to false if you have custom gripper fingers. true true, false
external_urdf_loc the file path to the custom urdf.xacro file that you would like to include in the Interbotix robot's urdf.xacro file. ''  
hardware_type configures the robot_description to use the actual hardware, fake hardware, or hardware simulated in Gazebo. actual actual, fake, gz_classic
robot_description URDF of the robot; this is typically generated by the xacro command. Command(FindExec(xacro) + ' ' + LocalVar('FindPackageShare(pkg= interbotix_xslocobot_descriptions) + 'urdf' + 'locobot.urdf.xacro'') + ' ' + 'arm_model:=' + LaunchConfig(arm_model) + ' ' + 'robot_name:=' + LaunchConfig(robot_name) + ' ' + 'base_model:=' + LaunchConfig(base_type) + ' ' + 'robot_model:=' + LaunchConfig(robot_model) + ' ' + 'use_gripper:=' + LaunchConfig(use_gripper) + ' ' + 'show_ar_tag:=' + LaunchConfig(show_ar_tag) + ' ' + 'show_gripper_bar:=' + LaunchConfig(show_gripper_bar) + ' ' + 'show_gripper_fingers:=' + LaunchConfig(show_gripper_fingers) + ' ' + 'use_lidar:=' + LaunchConfig(use_lidar) + ' ' + 'external_urdf_loc:=' + LaunchConfig(external_urdf_loc) + ' ' + 'hardware_type:=' + LaunchConfig(hardware_type) + ' ')  

To understand how the joystick buttons map to controlling the robot, look at the diagram and table below:


Base Control Mode

Button Action
Left Stick Up/Down drive the mobile base forward/backward between 0.7 to -0.7 m/s
R2 rotate the mobile base clockwise between 0 and -3.14 rad/s
L2 rotate the mobile base counterclockwise between 0 and 3.14 rad/s
Right Stick Up/Down tilt the camera Up/Down
Right Stick Left/Right pan the camera Left/Right
START/OPTIONS move the pan/tilt servo to '0' radians

Arm Control Mode

Button Action
START/OPTIONS move robot arm to its Home pose
SELECT/SHARE move robot arm to its Sleep pose
R2 rotate the 'waist' joint clockwise
L2 rotate the 'waist' joint counterclockwise
Triangle increase gripper pressure in 0.125 step increments (max is 1)
X decrease gripper pressure in 0.125 step increments (min is 0)
O open gripper
Square close gripper
Right Stick Up/Down increase/decrease pitch of the end-effector
Right Stick Left/Right increase/decrease roll of the end-effector
R3 reverses the Right Stick Left/Right control
Left Stick Up/Down move the end-effector (defined at 'ee_gripper_link') vertically in Cartesian space
Left Stick Left/Right move the end-effector (defined at 'ee_gripper_link') horizontally in Cartesian space
L3 reverses the Left Stick Left/Right control
R1 if the arm has 6dof, this moves the end-effector in a negative direction along its own 'y' axis
L1 if the arm has 6dof, this moves the end-effector in a positive direction along its own 'y' axis

Both Modes

Button Action
D-pad Up increase the control loop rate in 1 Hz step increments (max of 40)
D-pad Down decrease the control loop rate in 1 Hz step increments (min of 10)
D-pad Left 'coarse' control - sets the control loop rate to a user-preset 'fast' rate
D-pad Right 'fine' control - sets the control loop rate to a user-preset 'slow' rate
PS shift to the other Control Mode