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model_completion

Package Summary

Documented

model_completion

Package Summary

Documented

model_completion

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Description

This tutorial describes how to use an in hand object modeling on a PR2 robot in order to obtain models of unknown objects based on the data collected with an RGB camera observing the robot’s hand while moving the object. The goal is to develop the technique that enables robots to autonomously acquire models of unknown objects, thereby increasing understanding. Ultimately, such a capability will allow robots to actively investigate their environments and learn about objects in an incremental way, adding more and more knowledge over time.

Prerequisite

- Put the object in PR2's gripper and bring the object into the field of view of the camera. Make sure the background is neutral (e.g. white wall).

- Rotate the gripper around its approach axis. You can use our provided script (TBD) or write one on your own.

- Install robot_mask package.

Usage

To extract the appearance models of the rotated object we will be using the following launch file:

   1   <launch>
   2         <node  pkg="model_completion" type="in_hand_modeling" name="get_mask_client" output="screen"  >
   3         <param name="width" value="640" />
   4         <param name="height" value="480" />
   5         <param name="fovy" value="47" />
   6         <param name="camera_frame" value="openni_rgb_optical_frame" />
   7         <param name="image_topic" value="/camera/rgb/image_mono" />
   8         <param name="save_images" value="true" />
   9         <param name="tf_topic" value="/tf" />
  10         <param name="min_nn" value="5" />       
  11         <param name="knn" value="4" />
  12         <param name="mode" value="knn_search" />
  13         </node>
  14         <param name="robot_description" textfile="$(find model_completion)/robot/robot.xml"/>
  15         <node  pkg="robot_mask" type="robot_mask" name="robot_mask" output="screen" >
  16         </node>
  17 </launch>

There are several parameters that control the object modeling process:

  • width, height, fovy - are the width, height and vertical focal length of the camera used;

  • image_topic - input images topic;

  • tf_topic - robot's TF tree;

  • save_images - a parameter to save the images (by default saved in the home/.ros folder);

  • min_nn - an integer value for the minimum number of neighbors allowed when using the radiusSearch function;

  • knn - the number of neighbors searched with knnSearch function;

  • mode - which function to use to get rid of outlier features. Options are: "manual", "radius_search", "knn_search" (see an explanation below on the meaning of the parameters);

  • robot_description - upload robot's URDF if working on rosbags.

To start the program run:

$ roslaunch model_completion getMask.launch

The overview of the program can be seen in the following figure:

system_overview55.jpg

Intuition Behind the Use of radiusSearch and knnSearch

As it can be seen, images contain a considerable number of outliers (see figure below), especially on the robot's gripper and the goal is to remove these SIFT features through nearest-neighbor search. We are going to use two methods: radius search and knn search. For this all the features need to be extracted in order to check the nearest neighbors in a specified radius for the first method and a specified number of neighbors for the second one. For good results in obtaining our templates (on 640x480 images) we vary the radius between 20 and 30 pixels and the number of neighbors between 2 and 5. After removing the outlier features it is trivial to extract the region of interest by computing a bounding-box rectangle around the inlier features.

outliers_visualization2.jpg

Wiki: model_completion (last edited 2011-05-25 18:39:55 by Dejan Pangercic)