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 in QtCreator.
  • Remove the first 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 the supporting nodes with the launch file:

    roslaunch collision_avoidance_pick_and_place ur5_setup.launch
  • In another terminal, 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