Update configuring-mppic.rst

Signed-off-by: Steve Macenski <[email protected]>

Author: SteveMacenski

configuration/packages/configuring-mppic.rst

@@ -1140,7 +1140,7 @@ Otherwise, the parameters have been closely pre-tuned by your friendly neighborh
 Prediction Horizon, Costmap Sizing, and Offsets
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-As this is a predictive planner, there is some relationship between maximum speed, prediction times, and costmap size that users should keep in mind while tuning for their application. If a controller server costmap is set to 3.0m in size, that means that with the robot in the center, there is 1.5m of information on either side of the robot. When your prediction horizon (``time_steps * model_dt``) at maximum speed (``vx_max``) is larger than this, then your robot will be artificially limited in its maximum speeds and behavior by the costmap limitation. For example, if you predict forward 3 seconds (60 steps @ 0.05s per step) at 0.5m/s maximum speed, the **minimum** required costmap radius is 1.5m - or 3m total width.
+As this is a predictive planner, there is some relationship between maximum speed, prediction times, std sampling, and costmap size that users should keep in mind while tuning for their application. If a controller server costmap is set to 3.0m in size, that means that with the robot in the center, there is 1.5m of information on either side of the robot. When your prediction horizon (``time_steps * model_dt``) at maximum speed (``vx_max``) is larger than this, then your robot will be artificially limited in its maximum speeds and behavior by the costmap limitation. For example, if you predict forward 3 seconds (60 steps @ 0.05s per step) at 0.5m/s maximum speed, the **minimum** required costmap radius is 1.5m - or 3m total width. The faster the robot is set to go, the higher the velocity sampling standard deviations should be in order to effectively explore the velocity space.
 
 The same applies to the Path Follow and Align offsets from furthest. In the same example if the furthest point we can consider is already at the edge of the costmap, then further offsets are thresholded because they're unusable. So its important while selecting these parameters to make sure that the theoretical offsets can exist on the costmap settings selected with the maximum prediction horizon and velocities desired. Setting the threshold for consideration in the path follower + goal critics as the same as your prediction horizon can make sure you have clean hand-offs between them, as the path follower will otherwise attempt to slow slightly once it reaches the final goal pose as its marker.