Is an IMU required to run Turtlebot stack?

asked 2011-04-16 06:45:41 -0500

Scott
693 ●33 ●45 ●53

Is an IMU required to run the Turtlebot stack? If so, what would be the recommended IMU to buy?

Thanks, -Scott

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Issues with IMU odometry. I purchased and mounted the ADXRS613 as recommended below, but I am getting the following errors. As you can guess, the mapping is still off and it is likely due to the IMU not helping out with improved data due to the errors. Any help would be appreciated.

Scott ( 2011-04-23 01:53:17 -0500 )edit

Here are the errors I get on turtlebot_bringup [ERROR] [1303566596.868810887]: Timestamps of odometry and imu are 1.218011 seconds apart. [ERROR] [1303566596.869189147]: filter time older than imu message buffer [ERROR] [1303566597.380293912]: Could not transform imu message from to base_footprint

Scott ( 2011-04-23 01:53:35 -0500 )edit

Are you running different nodes on different machines? If so it sounds like you have a clock skew problem. Try setting up NTP/chrony: http://www.ros.org/wiki/Robots/TurtleBot/diamondback/Robot%20Setup#Setup_NTP

JeffRousseau ( 2011-04-25 00:37:13 -0500 )edit

PS Unless you have a really good network connection between nodes (underutilized 802.11N network) I'd suggest running the entire nav stack on a single machine.

JeffRousseau ( 2011-04-25 00:40:29 -0500 )edit

Also, you'll have to comment out the URDF part of the create_bringup and replace it with your own (probably static) transforms for the Kinect and the imu (turtlebot calls the imu frame gyro_link)--unless you've somehow recreated the turtlebot in its entirety

JeffRousseau ( 2011-04-25 01:04:46 -0500 )edit

Great suggestions. I will give them a go and see if that helps. Much appreciated.

Scott ( 2011-04-26 05:14:08 -0500 )edit

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answered 2011-04-18 06:57:23 -0500

JeffRousseau
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updated 2011-06-23 05:34:57 -0500

The Turtlebot uses a single-axis ADXRS613 rate gyro for its IMU, attached directly to the DB25 analog port of the iRobot Create base. I'm using an ADXRS613 breakout from sparkfun found here on my (non-turtelbot) Create--works great.

Hook the RATE pin from the ADXRS613 to the Analog Input (pin 4), connect the 5V on the breakout to the 5V on the DB25, and hook the GNDs together as well. Ignore the other pins on the ADXRS613 unless you want to figure out temperature compensation.

Also, make sure you run the Turtlebot calibration node to compensate for bias in the IMU. You should only have to do this once unless you drive your robot in varying environments--as the calibration routine compensates for wheel slippage as well as rate bias.

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