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== PACKAGE: haf_grasping == ==========================================================

Author: David Fischinger, Vienna University of Technology Version: 1.0 Date: 15.5.2015

HAF_GRASPING is calculating grasp points for unknown and known objects represented by the surface point cloud data. For scientific foundation see: D. Fischinger, M. Vincze: “Learning Grasps for Unknown Objects in Cluttered Scenes”, IEEE International Conference on Robotics and Automation (ICRA), 2013. [pdf] D. Fischinger, A. Weiss, M. Vincze: “Learning Grasps with Topographic Features”, The International Journal of Robotics Research.

In a first step the point cloud is read from a ROS topic and a heightsgrid is created. For each 14x14 square of the hightsgrid a featurevector is created. Using SVM with an existing model file, it is predicted if the center of the square is a good grasping point. For good grasping points the coordinates and the direction of the approach vectors are published.

DOWNLOAD CODE

git

HOW TO USE HAF_GRASPING - GET STARTED

Start calculation server (does the work), haf_client (small programming incl. class that shows how to use haf_grasping) and a visualization in rviz:

roslaunch haf_grasping haf_grasping_all.launch

Publish the path of a point cloud to calculate grasp points on this object with the gripper approaching direction along the z-axis:

rostopic pub /haf_grasping/input_pcd_rcs_path std_msgs/String “$(rospack find haf_grasping)/data/pcd2.pcd” -1

(Alternatively, publish a point cloud at the ros topic: /haf_grasping/depth_registered/single_cloud/points_in_lcs)

EXPLANATION FOR THE RVIZ VISUALIZATION

RVIZ will now visualize the point cloud with corresponding frame (blue indicates the z-axis). Bigger rectangle: indicates the area where heights can be used for grasp calculation Inner rectangle: defines the area where grasps (grasp centers) are searched. Long red line: indicates the closing direction (for a two finger gripper) Red/green spots: indicate the positions where grasps are really tested for the current gripper roll (ignoring points where no calculation is needed, e.g. no data there) Green bars: indicate where possible grasps were found. The height of the bars indicate an grasp evaluation score (the higher the better) Black arrow: indicates the best grasp position found and the approching direction (for a parallel two finger gripper)

HAF-GRASPING CLIENT - CODE EXPLAINDED

In calc_grasppoints_action_client.cpp we subscribe to a point_cloud topic and start the following callback when a point cloud comes in:

== code start ==

//get goal (input point cloud) for grasp calculation, send it to grasp action server and receive result void CCalcGrasppointsClient::get_grasp_cb(const sensor_msgs::PointCloud2ConstPtr& pc_in) { ROS_INFO(“\nFrom calc_grasppoints_action_client: point cloud received”);

// create the action client
// true causes the client to spin its own thread
actionlib::SimpleActionClient<haf_grasping::CalcGraspPointsServerAction> ac("calc_grasppoints_svm_action_server", true);

ROS_INFO("Waiting for action server to start.");
// wait for the action server to start
ac.waitForServer(); //will wait for infinite time

ROS_INFO("Action server started, sending goal.");
// send a goal to the action
haf_grasping::CalcGraspPointsServerGoal goal;
goal.graspinput.input_pc = *pc_in;

goal.graspinput.grasp_area_center = this->graspsearchcenter;

// set size of grasp search area
goal.graspinput.grasp_area_length_x = this->grasp_search_size_x+14;
goal.graspinput.grasp_area_length_y = this->grasp_search_size_y+14;

// set max grasp calculation time
goal.graspinput.max_calculation_time = this->grasp_calculation_time_max;

//send goal
ac.sendGoal(goal);

//wait for the action to return
bool finished_before_timeout = ac.waitForResult(ros::Duration(50.0));

if (finished_before_timeout)
{
    actionlib::SimpleClientGoalState state = ac.getState();
    boost::shared_ptr<const haf_grasping::CalcGraspPointsServerResult_<std::allocator<void> > > result = ac.getResult();
    ROS_INFO("Result: %s", (*(result)).result.data.c_str());
    ROS_INFO("Action finished: %s",state.toString().c_str());
}

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