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TurtleBot Odometry and Gyro Calibration

Description: This will show you how to calibrate or test the calibration of a TurtleBot which is highly recommended when running any navigation based application.

Tutorial Level: BEGINNER

Next Tutorial: SLAM Map Building with TurtleBot

Setup

First position TurtleBot at the center of a long straight wall (at least 2 meters long), facing towards the wall, at about 30 cm away from the wall.

• 

Execution

This assumes you have already started the robot

Now ssh (ssh help) (ssh help) into the TurtleBot and run the calibration routine:

• To ssh in to a TurtleBot from a workstation computer:

  • determine the IP_OF_TURTLEBOT by using ifconfig (Need more help) (Need more help)

    To determine a computer's IP address and network interface in linux:

    • ifconfig

    You will see something like:

    • lo        Link encap:Local Loopback  
                inet addr:127.0.0.1  Mask:255.0.0.0
                inet6 addr: ::1/128 Scope:Host
                UP LOOPBACK RUNNING  MTU:16436  Metric:1
                RX packets:6658055 errors:0 dropped:0 overruns:0 frame:0
                TX packets:6658055 errors:0 dropped:0 overruns:0 carrier:0
                collisions:0 txqueuelen:0 
                RX bytes:587372914 (587.3 MB)  TX bytes:587372914 (587.3 MB)
      
      wlan1     Link encap:Ethernet  HWaddr 48:5d:60:75:58:90  
                inet addr:10.0.129.17  Bcast:10.0.129.255  Mask:255.255.254.0
                inet6 addr: fe80::4a5d:60ff:fe75:5890/64 Scope:Link
                UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
                RX packets:101983 errors:0 dropped:0 overruns:0 frame:0
                TX packets:37244 errors:0 dropped:0 overruns:0 carrier:0
                collisions:0 txqueuelen:1000 
                RX bytes:49326141 (49.3 MB)  TX bytes:7588044 (7.5 MB)

    • the network interface for the wireless card is wlan1

    • the IP address of the computer is 10.0.129.17

    
    

  • use ssh to connect to the TurtleBot

    ssh turtlebot@IP_OF_TURTLEBOT

  
  

roslaunch turtlebot_calibration calibrate.launch

Turtlebot will perform a number of calibration spins. When it finishes, you'll see a print on the screen like this:

• [INFO] [WallTime: 1299286750.821002] Multiply the 'turtlebot_node/gyro_scale_correction' parameter with 1.002262
  [INFO] [WallTime: 1299286750.822427] Multiply the 'turtlebot_node/odom_angular_scale_correction' parameter with 1.000263

• If the TurtleBot does not successfully return to facing the wall before executing the next rotation the data will be incorrect. This can be caused by too big of an error in the existing parameters. If it under rotates, increase the odom parameter and retry. If it over rotates, lower the odom_parameter and retry.

Results

The calibration routine will output 2 numbers. The correction for the gyro and the correction for the odometry. The values are factors to multiply with the current parameters to get the best results (see also this QA and this QA).

After running the calibration set the parameters to the old value multiplied by the correction.

The two parameters are:

• turtlebot_node/gyro_scale_correction
• turtlebot_node/odom_angular_scale_correction

For a single run you can set the parameters using dynamic_reconfigure:

• rosrun dynamic_reconfigure reconfigure_gui 

Then select the turtlebot_node and set the parameters.

To persist these parameters between runs it is recommended to edit the turtlebot.launch file in /etc/ros/electric.

• sudo emacs -nw turtlebot.launch

Once the .launch file is modified, you need to restart the turtlebot service in order to reflect the change.