Open Gripper

In this exercise, the objective is to use a “grasp action client” to send a grasp goal that will open the gripper.

Locate Function

• In the main program, locate the function call to application.set_gripper().
• Go to the source file of that function by clicking in any part of the function and pressing “F2”.
• Remove the fist line containing the following ROS_ERROR_STREAM ... so that the program runs.

Complete Code

• Find every line that begins with the comment Fill Code: and read the description. Then, replace every instance of the comment ENTER CODE HERE with the appropriate line of code.

/* Fill Code:
     .
     .
     .
*/
/* ========  ENTER CODE HERE ======== */

• The grasp_goal.goal property can take on three possible values:

    grasp_goal.goal = object_manipulation_msgs::GraspHandPostureExecutionGoal::GRASP;
    grasp_goal.goal = object_manipulation_msgs::GraspHandPostureExecutionGoal::RELEASE;
    grasp_goal.goal = object_manipulation_msgs::GraspHandPostureExecutionGoal::PRE_GRASP;

• Once the grasp flag has been set you can send the goal through the grasp action client

Build Code and Run

• Compile the pick and place node:
  • in QTCreator: Build -> Build Project
  • Alternatively, in a terminal:

catkin build collision_avoidance_pick_and_place

• Run your node with the launch file:

roslaunch collision_avoidance_pick_and_place ur5_pick_and_place.launch

• If the task succeeds you will see something like the following in the terminal (below). The robot will not move, only gripper I/O is triggered:

[ INFO] [1400553290.464877904]: Move wait Succeeded
[ INFO] [1400553290.720864559]: Gripper opened
[ERROR] [1400553290.720985315]: detect_box_pick is not implemented yet.  Aborting.

API References

sendGoal()