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Examine Kobuki

melodic noetic   Show EOL distros: 

New in groovy

Overview

In this tutorial you will learn how to start the basic software for Kobuki, inspect the sensors' state and send commands.

Launch Kobuki

First, start minimal.launch to bring up Kobuki's basic software (bootstrap layer). We use the argument --screen to get verbose output in the terminal.

> roslaunch kobuki_node minimal.launch --screen

This launch file starts a nodelet manager and loads the Kobuki nodelet (the ROS wrapper around Kobuki's driver).

Examine the topics

Next, take a look at Kobuki's topics.

$ rostopic list
/diagnostics
/diagnostics_agg
/diagnostics_toplevel_state
/joint_states
/mobile_base/commands/digital_output
/mobile_base/commands/external_power
/mobile_base/commands/led1
/mobile_base/commands/led2
/mobile_base/commands/motor_power
/mobile_base/commands/reset_odometry
/mobile_base/commands/sound
/mobile_base/commands/velocity
/mobile_base/debug/raw_data_command
/mobile_base/debug/raw_data_stream
/mobile_base/events/bumper
/mobile_base/events/button
/mobile_base/events/cliff
/mobile_base/events/digital_input
/mobile_base/events/power_system
/mobile_base/events/robot_state
/mobile_base/events/wheel_drop
/mobile_base/sensors/bump_pc
/mobile_base/sensors/core
/mobile_base/sensors/dock_ir
/mobile_base/sensors/imu_data
/mobile_base/sensors/imu_data_raw
/mobile_base/version_info
/odom
/rosout
/rosout_agg
/tf

/mobile_base/commands/controller_info
/mobile_base/controller_info

As you see, Kobuki's data in- and output follows a structure:

• <node_name>/sensor/: Continuous streams of the sensor's data (note that /odom and /joints_states are remapped by default, since they are widley used at the highest level/namespace)

• <node_name>/events/: If a sensor changes its state, e.g. bumper pressed/released, the new state is published here.

• <node_name>/commands/: Use these topics to make Kobuki do things like switch on LEDs, playing sounds and driving around.

• <node_name>/debug/: Outputs detailed info about a lot of Kobuki's internals.

Check sensors

Let's try out some topics.

• Check the bumpers: Listen to the bumper topic, then tap one of the bumpers.

  $ rostopic echo /mobile_base/events/bumper 
  state: 1
  bumper: 2
  ---
  state: 0
  bumper: 2
  ---

• Check the wheel drop sensors: Listen to the wheel drop sensor topic, then lift up and put down Kobuki.

  $ rostopic echo /mobile_base/events/wheel_drop 
  state: 1
  wheel: 0
  ---
  state: 1
  wheel: 1
  ---
  state: 0
  wheel: 0
  ---
  state: 0
  wheel: 1
  ---

• Check the IMU: Listen to the imu sensor topic, then turn Kobuki.

  $ rostopic echo /mobile_base/sensors/imu_data
  header: 
    seq: 0
    stamp: 
      secs: 1355022789
      nsecs: 36483345
    frame_id: gyro_link
  orientation: 
    x: 0.0
    y: 0.0
    z: 0.28769484546
    w: 0.957722128749
  orientation_covariance: [1.7976931348623157e+308, 0.0, 0.0, 0.0, 1.7976931348623157e+308, 0.0, 0.0, 0.0, 0.005]
  angular_velocity: 
    x: 0.0
    y: 0.0
    z: 0.000349065850399
  angular_velocity_covariance: [1.7976931348623157e+308, 0.0, 0.0, 0.0, 1.7976931348623157e+308, 0.0, 0.0, 0.0, 0.005]
  linear_acceleration: 
    x: 0.0
    y: 0.0
    z: 0.0
  linear_acceleration_covariance: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
  ---

Trigger stuff

Roboticists want to do things. So, let's do it!

Remark: rostopic pub works create with tab completion!

• Change the color or turn off a LED: Publish to the LED command topic. The available commands are:
  • 0 - off
  • 1 - green
  • 2 - orange
  • 3 - red
  For example:

  $ rostopic pub /mobile_base/commands/led1 kobuki_msgs/Led "value: 1"
  $ rostopic pub /mobile_base/commands/led1 kobuki_msgs/Led "value: 0"

• Play a sound: Publish to the sound command topic. The available sequences are:
  • 0 - turn on
  • 1 - turn off
  • 2 - recharge start
  • 3 - press button,
  • 4 - error sound
  and the nostalgic section...
  • 5 - start cleaning
  • 6 - cleaning end
  For example:

  $ rostopic pub /mobile_base/commands/sound kobuki_msgs/Sound "value: 6"

• Make the turtle snap!: Publish to the velocity command topic.

  rostopic pub /mobile_base/commands/velocity geometry_msgs/Twist "linear:
    x: 0.1
    y: 0.0
    z: 0.0
  angular:
    x: 0.0
    y: 0.0
    z: 0.0"

What's next

Now that you know how to launch the basics and work with Kobuki, it's time to take it for a ride.