[ros-users] AMCL configuration details required

[Prasad Dixit]

Hello all,

I have boxturtle package in which AMCL package 
/navigation/amcl/example/amcl_diff.launch has got below configuration:

<launch>
<node pkg="amcl" type="amcl" name="amcl">
  <!-- Publish scans from best pose at a max of 10 Hz -->
  <param name="odom_model_type" value="diff"/>
  <param name="odom_alpha5" value="0.1"/>
  <param name="transform_tolerance" value="0.2" />
  <param name="gui_publish_rate" value="10.0"/>
  <param name="laser_max_beams" value="30"/>
  <param name="min_particles" value="500"/>
  <param name="max_particles" value="5000"/>
  <param name="kld_err" value="0.05"/>
  <param name="kld_z" value="0.99"/>
  <param name="odom_alpha1" value="0.2"/>
  <param name="odom_alpha2" value="0.2"/>
  <!-- translation std dev, m -->
  <param name="odom_alpha3" value="0.8"/>
  <param name="odom_alpha4" value="0.2"/>
  <param name="laser_z_hit" value="0.5"/>
  <param name="laser_z_short" value="0.05"/>
  <param name="laser_z_max" value="0.05"/>
  <param name="laser_z_rand" value="0.5"/>
  <param name="laser_sigma_hit" value="0.2"/>
  <param name="laser_lambda_short" value="0.1"/>
  <param name="laser_lambda_short" value="0.1"/>
  <param name="laser_model_type" value="likelihood_field"/>
  <!-- <param name="laser_model_type" value="beam"/> -->
  <param name="laser_likelihood_max_dist" value="2.0"/>
  <param name="update_min_d" value="0.2"/>
  <param name="update_min_a" value="0.5"/>
  <param name="odom_frame_id" value="odom"/>
  <param name="resample_interval" value="1"/>
  <param name="transform_tolerance" value="0.1"/>
  <param name="recovery_alpha_slow" value="0.0"/>
  <param name="recovery_alpha_fast" value="0.0"/>
</node>
</launch>

I have some(too many!) unclear points as below:
1. If Laser model type "Beam" is commented then why laser_z_short, 
laser_z_max parameters are active?
2. "laser_likelihood_max_dist" parameter depicts likehood model in use. 
Considering entire nav stack is costmap_common's parameter 
"inflation_radius" should be same as likehood_max_dist?
3. Which is model can give accurate measurement beam or likehood?
4. Translational/ Rotational movements are required before performing a 
filter update by update_min_d and update_min_a. Are values against these 
parameters (0.2  and 0.5 resp.) in meters? are these parameters active 
because we have not given initial position?
5. transform_tolerance is specified twice with two different values.

Hope your experienced replies will give us right direction.

- Prasad Dixit

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