AMCL odom_alpha parameters

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Hi,

I'm currently trying to "fix" the localization on a known map with my car-like robot. I don't need it to be very accurate, "in about" will do. My current settings are as follows:

<param name="odom_alpha1" value="0.2"/>
<param name="odom_alpha2" value="0.3"/>
<param name="odom_alpha3" value="0.6"/>
<param name="odom_alpha4" value="0.4"/>

but since I'm not a robotics pro I have a hard time understanding what I need to tune in my case. Some info about my robot:

• car-like robot, 4 wheels
• I can control 2 wheels at a time (so either the left or the right side), making a turn means turning the left and the right side in opposite directions
• the speed of the left and right side is usually a bit different, this means that the robot is not going straight forward but driving a small curve
• I have a gyro that works pretty good, so that I can calculate yaw, BUT the speed is just an estimated value

If I understood it correctly odom_alpha1 is not very important for me, since the gyro gives me pretty good values.

odom_alpha2 whould "take care" of the drift mentioned in the 3rd bullet point, right?

odom_alpha3 corrects the forward movement?

and odom_alpha4 corrects the forward/backward movement, when making a turn.

Did I get it right? Which parameters I should work with, since my robot is still getting lost pretty often.