Build a MoveIt! Package¶

In this exercise, we will create a MoveIt! package for an industrial robot. This package creates the configuration and launch files required to use a robot with the MoveIt! Motion-Control nodes. In general, the MoveIt! package does not contain any C++ code.

NOTE: The “MoveIt Setup Assistant” is not available in ROS 2 distributions before Humble. A workaround for earlier distributions is to use the ROS 1 version, have it output a ROS1-compatible package, and to adapt the output for ROS2 (as we did in previous versions of this training).

Motivation¶

MoveIt! is a free-space motion planning framework for ROS. It’s an incredibly useful and easy-to-use tool for planning motions between two points in space without colliding with anything. Under the hood MoveIt is quite complicated, but (unlike most ROS libraries) it has a really nice GUI Wizard to get you started.

Reference Example¶

Using MoveIt with ROS-I

Further Information and Resources¶

MoveIt Setup Assistant Tutorial

Scan-N-Plan Application: Problem Statement¶

In this exercise, you will generate a MoveIt package for the UR5 workcell you built in a previous step. This process will mostly involve running the MoveIt! Setup Assistant. At the end of the exercise you should have the following:

A new package called myworkcell_moveit_config
A moveit configuration with one group (“manipulator”), that consists of the kinematic chain between the UR5’s base_link and tool0.

Scan-N-Plan Application: Guidance¶

Create a Base Package using the Setup Assistant¶

Install the MoveIt 2 Humble packages:
```
sudo apt install ros-humble-moveit
```
Source your workspace and start the MoveIt! Setup Assistant (don’t forget auto-complete with tab):
```
ros2 launch moveit_setup_assistant setup_assistant.launch.py
```
Select “Create New MoveIt Configuration Package”, select the workcell.urdf.xacro in your workspace’s myworkcell_support package, then “Load File”.
Work your way through the tabs on the left from the top down.
1. Generate a self-collision matrix.
2. Add a fixed virtual base joint. e.g.
```
name = 'FixedBase' (arbitrary)
child = 'world' (should match the URDF root link)
parent = 'world' (reference frame used for motion planning)
type = 'fixed'
```
3. Add a planning group called manipulator that names the kinematic chain between base_link and tool0. Note: Follow ROS naming guidelines/requirements and don’t use any whitespace, anywhere.
  1. Set the kinematics solver to KDLKinematicsPlugin
  2. Set the default OMPL planner to RRTConnect
4. Create a few named positions (e.g. “home”, “allZeros”, etc.) to test with motion-planning.
5. Don’t worry about adding end effectors, passive joints, or ros2_control URDF modifications for this exercise.
6. In the “ROS 2 Controllers” tab, use the “Auto Add JointTrajectoryController” button to define a basic JointTrajectoryController controller for the entire UR5 arm.
7. In the “MoveIt Controllers” tab,use the “Auto Add FollowJointsTrajectory” button to define a basic FollowJointTrajectory controller for the UR5 arm.
8. Skip the “Perception” and “Launch Files” tabs.
9. Enter author / maintainer info.
  
  Yes, it’s required, but doesn’t have to be valid.
10. Generate a new package and name it myworkcell_moveit_config.
  - make sure to create the package inside your ros2_ws/src directory

Update the Setup Assistant Output¶

The outcome of the Setup Assistant is a new ROS2 package that contains a large number of launch and configuration files. We need to add just a bit more to customize this general-purpose package for our application.

Create a new file in your myworkcell_moveit_config package named config/ompl_planning.yaml. Paste in the following code:

manipulator:
  default_planner_config: RRTConnect
  planner_configs:
    - AnytimePathShortening
    - SBL
    - EST
    - LBKPIECE
    - BKPIECE
    - KPIECE
    - RRT
    - RRTConnect
    - RRTstar
    - TRRT
    - PRM
    - PRMstar
    - FMT
    - BFMT
    - PDST
    - STRIDE
    - BiTRRT
    - LBTRRT
    - BiEST
    - ProjEST
    - LazyPRM
    - LazyPRMstar
    - SPARS
    - SPARStwo
  projection_evaluator: joints(shoulder_pan_joint,shoulder_lift_joint)
  longest_valid_segment_fraction: 0.005

planning_plugin: 'ompl_interface/OMPLPlanner'
request_adapters: >-
    default_planner_request_adapters/AddTimeOptimalParameterization
    default_planner_request_adapters/FixWorkspaceBounds
    default_planner_request_adapters/FixStartStateBounds
    default_planner_request_adapters/FixStartStateCollision
    default_planner_request_adapters/FixStartStatePathConstraints
start_state_max_bounds_error: 0.1

Make sure your editor does not change the amount of whitespace at the front of these lines.

You may wish to examine some key files in your new package:

workcell.srdf: This file defines additional information about the workspace links and joints such as planning groups, end-effectors, virtual joints, and allowed collisions.
kinematics.yaml: These parameters define the kinematics solver used to find joint angles for a given cartesian position.
ompl_planning.yaml: This informs MoveIt on what planner profiles are available for our manipulator and provides some additional configuration parameters.
moveit_controllers.yaml: This file will configure MoveIt to use a controller for joint trajectory execution provided by ros2_control.
ros2_controllers.yaml: These parameters configure the ROS 2 Control nodes at startup.

Rebuild the workspace (colcon build) and test a launch file to see if the new package loads without errors:
```
source ~/ros2_ws/install/setup.bash
ros2 launch myworkcell_moveit_config demo.launch.py
```

Don’t worry too much about how to use RViz. We’ll work through that in the next exercise.

Challenge Exercises¶

Imagine you have misrepresented your robot and need to add an additional joint. Would it be faster to make minor edits to all configuration files or to re-do the MoveIt package creation process? Try each method and compare.