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Overview

visp_hand2eye_calibration is a ROS package that computes extrinsic camera parameters : the constant transformation from the hand to the camera coordinates.

Let's consider a camera attached to a robotic hand, as shown in the following diagram:

The interest of this package is to perform the hand to eye calibration part.

To do so, two sets of transformations are fed to the calibrator node.

• a list of camera-to-object transformations
• a list of world to hand transformations

Once the node has enough transformations, it can estimate the camera-to-hand transformation which is the goal of the calibration.

The package consists of a calibrator node and an experimental client doing a sample calibration from a few poses.

The experimental client is merely there for a quick demonstration of the package abilities.

Installation

visp_hand2eye_calibration is part of vision_visp stack.

• To install visp_hand2eye_calibration package run

  sudo apt-get install ros-$ROS_DISTRO-visp-hand2eye-calibration

• Or to install the complete stack run

  sudo apt-get install ros-$ROS_DISTRO-vision-visp

Usage

To run the calibrator node:

rosrun visp_hand2eye_calibration visp_hand2eye_calibration_calibrator

Example

An example client is shipped with this package. It feeds different transformations (camera->object and world->hand) to the calibrator which computes the relative transformation between the the camera and the hand.

To try this example, run roscore first.

roscore

Then, run the client:

rosrun visp_hand2eye_calibration visp_hand2eye_calibration_client

Finally, run the calibrator:

rosrun visp_hand2eye_calibration visp_hand2eye_calibration_calibrator

The output displayed in the terminal running your client should look like this:

[ INFO] [1329226083.184531090]: Waiting for topics...
[ INFO] [1329226084.186233704]: 1) GROUND TRUTH:
[ INFO] [1329226084.186327570]: hand to eye transformation: 
translation: 
  x: 0.1
  y: 0.2
  z: 0.3
rotation: 
  x: 0.96875
  y: 0.0863555
  z: -0.0863555
  w: 0.215889


[ INFO] [1329226085.186682976]: 2) QUICK SERVICE:
[ INFO] [1329226085.188853282]: hand_camera: 
translation: 
  x: 0.1
  y: 0.2
  z: 0.3
rotation: 
  x: 0.96875
  y: 0.0863555
  z: -0.0863555
  w: 0.215889

[ INFO] [1329226085.188915366]: 3) TOPIC STREAM:
[ INFO] [1329226085.190303537]: hand_camera: 
translation: 
  x: 0.1
  y: 0.2
  z: 0.3
rotation: 
  x: 0.96875
  y: 0.0863555
  z: -0.0863555
  w: 0.215889

Nodes

calibrator

Subscribed Topics

• transformation between the world and the hand frame. The node expects to receive several of those transformations.

• transformation between the camera and the object frame. The node expects to receive several of those transformations.

Services Called

• Returns the hand to camera transformation result after calibration based on the data published on the subscribed topics.

• Returns the hand to camera transformation result after calibration. This service is not based on the data published on the subscribed topics. Instead, the transformation are passed as service parameters.

• Reset all the data published on the subscribed topics. Only new publications (transformations) will be taken into account.