Move Arm to Wait Position

MoveIt!’s moveit_cpp API allows us to move the robot in various ways. With a PlanningComponent object, it is possible to create motion plans to move to a desired joint position, Cartesian goal or a predefined pose created with the Setup Assistant. Then we can use a MoveItCpp object to execute that plan. In this exercise, we will move the robot to a predefined joint pose.

Locate Function

  • In the main program, locate the method call to application.moveToWaitPosition().

  • Go to the source file of that function by clicking in any part of the function and pressing F2 in QtCreator.

  • Alternatively, browse to the file at

    [workspace source directory]/pick_and_place_application/src/tasks/move_to_wait_position.cpp

  • Remove the first line containing the following RCLCPP_ERROR ... 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 UNCOMMENT AND COMPLETE with the appropriate line of code.

    /* Fill Code:
    .
    .
    .
*/
/* UNCOMMENT AND COMPLETE: ... */

  • The name of the predefined “wait” pose was saved in the global variable cfg.WAIT_POSE_NAME during initialization.

  • Calling plan() provides a solution trajectory stored in a PlanSolution object

  • The execute() method sends a motion plan to the robot.

Build Code and Run

  • Compile the pick and place node:

    • In QTCreator: Build ‣ Build Project

    • Alternatively, in a terminal:

      cd ~/perception_driven_ws
colcon build

  • In a terminal, launch the supporting nodes:

    source ~/perception_driven_ws/install/setup.bash
ros2 launch pick_and_place_application application_setup.launch.py

  • In another terminal, launch the application node:

    source ~/perception_driven_ws/install/setup.bash
ros2 launch pick_and_place_application application_run.launch.py

  • If the robot is not already in the wait position, it should move to it.

In the terminal, you should see something like this:

[INFO] [1400553673.460328538] [pick_and_place_node]: Move wait Succeeded
[ERROR] [1400553673.460434627] [pick_and_place_node]: actuateGripper is not implemented yet. Aborting.

API References