Clearing the obstacles form local costmap

asked 2020-05-14 03:02:48 -0600

Yehor
166 ●39 ●49 ●49

updated 2020-05-14 04:57:15 -0600

Hello,

I want to ask, is it possible to specify somewhere in the move_base parameter how often clear the local costmap. I want to do that because I face the problem when the local costmap add a dynamic obstacles buy after the are disappeared the costmap do not clear the space too long.

On the image below I have marked the obstacles which have already gone but they are still persist on the local costmap.

image description

EDIT 1

local costmap parameters:

local_costmap: global_frame: odom robot_base_frame: base_footprint update_frequency: 5.0 publish_frequency: 1.0 static_map: false rolling_window: true width: 4.0 height: 4.0 resolution: 0.05

common costmap:

obstacle_range: 2.5 raytrace_range: 3.0 footprint: [[-0.2, -0.2], [-0.2, 0.2], [0.2, 0.2], [0.2, -0.2]] inflation_radius: 0.1 transform_tolerance: 1.0 observation_sources: laser_scan_sensor laser_scan_sensor: sensor_frame: laser_frame data_type: LaserScan topic: filtered_scan clearing: true marking: true min_obstacle_height: 0.1 max_obstacle_height: 0.4

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answered 2021-03-08 07:58:36 -0600

ParkerRobert
113 ●1 ●7 ●8

In order for the costmap to be able to clear obstacles, your observation source needs to "see" a distance greater than the distance from the observation source to the obstacle, this is part of the raytrace algorithm in the ROS Navigation stack.

Based on your parameters, it seems you have set all the right variables correctly:

obstacle_range: 2.5 < raytrace_range: 3.0 (raytrace_range should be more than obstacle_range)
marking and clearing are set to true
you can also try adding observation_persistence: 0.0 to ensure that obstacles are immediately cleared
check if your laser_scan_sensor has a maximum range value instead of inf or nan values. You can check this by doing a rostopic echo filtered_scan and inspecting the data (if you observe inf or nan values, you can use the http://wiki.ros.org/laser_filters package and use the LaserScanRangeFilter. Set the upper threshold to the max_range of your lidar and upper_replacement_value to max_range of your lidar

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answered 2020-05-14 20:48:11 -0600

942951641@qq.com

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maybe it is caused by a lidar which fov is less than 2pi

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No, The fov is 360 degree

Yehor ( 2020-05-15 01:06:13 -0600 )edit

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answered 2020-05-14 04:09:34 -0600

tianb03

710 ●16 ●39 ●33 https://github.com/tianbot

You'd better post your local costmap param configuration.

On your image, seems the robot cannot detect the obstacles behind. When there are no new sensor readings, the costmap will not be updated.

Try to increase the update_frequency and publish_frequency, also make sure that in the Observation sources, clearing is set to true.

I think this could solve your problem.

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@tianb03 I have updated the post with local and common costmap parameters. The update frequency is 5 Hz which should be enough.

Yehor ( 2020-05-14 04:58:18 -0600 )edit

@tianb03 Do the costmap treat the value from LaserScan 0.0 as a free area?

Yehor ( 2020-05-14 05:00:41 -0600 )edit

You can try to set the update frequecy as high as the laser scan frequency. Obstacle is calculated based on probability, so it wont disappear asap after the obastacle moves away. I cannot tell wether the laser can cover the obstacle area. But a 0.0 value can only assume it is unknown and wont update the costmap.

tianb03 ( 2020-05-14 07:20:53 -0600 )edit

@tianb03 What does it means: Obstacle is calculated based on probability? Could you explain please? And this: I cannot tell whether the laser can cover the obstacle area

Yehor ( 2020-05-14 08:58:22 -0600 )edit

1

Obstacles are generally NOT calculated based on probability. They disappear when you get laser readings behind them.

David Lu ( 2020-05-14 11:29:19 -0600 )edit

Thanks David for explaining. I just take for grant that the costmap occupancy is the same as the final map.

tianb03 ( 2020-05-14 22:40:08 -0600 )edit

@David Lu So will the costmap clear space if the value from LaserScan will be 0.0?

Yehor ( 2020-05-15 01:05:29 -0600 )edit

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