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acceptable % of odometry error of autonomy_create

asked 2017-06-05 04:34:29 -0500

fj138696 gravatar image

Hi All,

I am very new into understanding a lot of concepts in ROS, so far I have successfully ran autonomy_create software package and used a simple keyboard_node to drive my create2 robot.

So far this is what I have done. My linear velocity is 0.2 to drive create2 forward in typical square tile carpeted floor. When I subscribe to topic \odom, the initial value is as follows:

 pose: 
x: 0.000963
y: 0
z: 0
orientation:
x: 0
y: 0
z: 0
w: 1

I moved 1m forward and see if I can get 1meter value in my odom pose

 pose: 
x: 1.27661
y: -0.074605
z: 0
orientation:
x: 0
y: 0
z: -0.070646
w: 0.997501

I moved 1m forward again

    pose:  
x: 2.192413 
y: -0.298672 
z: 0
    orientation: 
x: 0 
y: 0 
z: -0.138908 
w: 0.990305

Based on simple calculation, 19cm is around 10% difference in 2m expected and even y position have some change in value.Currently, I got to know that odometry from wheel encoders alone is erroneous in nature that is why more complex processing is needed (EKF etc.,) now, I would like to know if this 10% error in odometry of autonomy_create that is acceptable to be as input in other package like robot_localization, AMCL etc?

I hope I could learn from you guys. Thanks in advance!

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Changes in y are usually because of changes in heading angle. What I do not understand is how you compared the odometry value to the real position of the robot.

Humpelstilzchen gravatar image Humpelstilzchen  ( 2017-06-06 01:07:08 -0500 )edit

I am trying to drive the robot in straight line marked by a tape on the floor. I aligned the bottom of the CLEAN button in the middle on the marked tape (which is only based on my visual estimation). Any suggestion to measure the change in x and y of the robot manually? thanks!

fj138696 gravatar image fj138696  ( 2017-06-06 21:37:32 -0500 )edit
1

Thats fine I guess. I glue plastic tape measures on the floor.

Humpelstilzchen gravatar image Humpelstilzchen  ( 2017-06-07 00:51:53 -0500 )edit

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answered 2017-06-05 21:51:09 -0500

DavidN gravatar image

My thoughts on this:

  1. If you have a good map and not-so-challenging environment, I think it is ok if your odometry is not so good, because you can always tune AMCL to perform localization intensively.
  2. If you have a good laser, you can consider using laser odometry to replace wheel odom completely. Hector SLAM ( http://wiki.ros.org/hector_slam ) and Laser Scan Matcher ( http://wiki.ros.org/laser_scan_matcher ) could be some good options.
  3. I personally think a good odometry should have error not more than 5%, most of the time should be less than 2%. A good option is to perform sensor fusion between your wheel odom and other sensor (gyro, IMU, laser odom...) using UKF or EKF which is part of robot_localization package itself.
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Or he could try to calibrate the odometry first e.g. with umbmark

Humpelstilzchen gravatar image Humpelstilzchen  ( 2017-06-06 00:52:23 -0500 )edit

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Asked: 2017-06-05 04:34:29 -0500

Seen: 439 times

Last updated: Jun 05 '17