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How to implement bumper pointcloud on a custom robot?

asked 2020-07-07 13:25:18 -0500

parzival gravatar image

I want to use the bumper information of my robot to add obstacles in the map. I have a custom robot and not a turtlebot so I can't simply use kobuki_bumper2pc. I tried reading the program and understanding their program, but I couldn't understand much.

I am getting the bumper pressed and released information for the two bumpers that I have on my robot. How do I use that to add obstacles in the costmap? I read about sensor_msgs/Pointcloud2 and I think I should convert my bumper messages to a pointcloud and add the pointcloud2 plugin in the costmap. But how to convert the bumper data to get the bumper pointcloud?

Lastly, since I want to use bumper data in mapping along with my laserscan, can I use this bumper pointcloud in gmapping as well? My other option is to use odometric navigation and store the global costmap, but it doesn't seem to be as accurate as gmapping obviously, Thanks

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answered 2020-07-08 09:03:18 -0500

jordan gravatar image

Take a look at this implementation of a "virtual bumper" that does essentially what you want, but by using comparison of the odometry and pose data to detect collisions (no bump sensors needed!).

The key part of the code that populates the pointcloud is:

  // place obstacle into point cloud 0.25 meters in front of robot
  float val = 0.25;
  memcpy(&pointcloud_.data[0 * pointcloud_.point_step + pointcloud_.fields[0].offset], &val, sizeof(float));
  val = 0.0;
  memcpy(&pointcloud_.data[0 * pointcloud_.point_step + pointcloud_.fields[1].offset], &val, sizeof(float));

  pointcloud_.header.stamp = ros::Time::now();
  pointcloud_pub_.publish(pointcloud_);

  collision_pub_.publish(true);

In the above, an obstacle is placed 0.25 meters in front of the robot (when a collision occurs), and with a Y translation of zero. Note: if you have left and right bumpers, you would add +/-Y numbers for that instead of zero.

To get it to work with gmapping, you could try converting the pointcloud into a laserscan and then publish that (on the same topic as the regular scan). There are tools for this conversion such as http://wiki.ros.org/pointcloud_to_laserscan

Here's the full implementation of the virtual bumper. It's a working standalone node that you could run without modification. It assumes you have pose and odometry data from somewhere. This was tested with the navigation stack and worked fine when used to populate the costmap obstacle layer.

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#include "ros/ros.h"
#include "nav_msgs/Odometry.h"
#include "geometry_msgs/Twist.h"
#include "geometry_msgs/PoseWithCovarianceStamped.h"
#include "tf/tf.h"
#include "std_msgs/Bool.h"
#include "sensor_msgs/PointCloud2.h"

class VirtualBumper
{
  public:
    VirtualBumper();
    virtual ~VirtualBumper() {};

  protected:
    void odomCallback ...
(more)
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Comments

Thanks for your answer! I'm however facing an issue with this. The pointcloud gets overwritten everytime there's a 'bump' event, which leads to oscillation in navigation when I add it to costmap obstacle layer. I instead want it to append the pointcloud, so it has all the bump events in account. How do I do that?

parzival gravatar image parzival  ( 2020-12-15 07:43:01 -0500 )edit

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Asked: 2020-07-07 13:25:18 -0500

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Last updated: Jul 08 '20