Understanding MoveIt!

MoveIt! provides RViz GUI plugin which can be used to generate motion plans and can directly interact with the robot. There is a demo launch file in the package to explore all the functionalities of this package. Open the terminal and type the following command.

roslaunch final_config demo.launch

The following window should open:

We can see several tabs on Motion Planning Window. In the Context tab the default motion planning library, OMPL, is loaded. If it is not loaded then we cannot perform motion planning.

Next is the Planning tab. This tab is used to set the Start State, Goal State, Plan a path, and execute the path. The GUI of the Planning tab is as follows:

Set the start state and the goal state of the robot under the Query panel. Click the Plan button to generate the motion plan from the start to the goal state. If the planning is successful, click on execute to execute it. By default, execution is done on fake controllers. These controllers must be replaced by trajectory controllers for executing the planned trajectory in Gazebo or the real robot. We can also set the time for planning, the number of planning attempts, goal tolerance and the workspace of the robot under the planning tab.

The interactive marker attached on the arm can be used to set the pose of the arm. We can translate and rotate the marker pose, and if there is a planning solution, we can see an arm in orange colour. In some situations, the arm will not move even the end effector marker pose moves, and if the arm does not come to the marker position, we can assume that there is no IK solution in that pose. We may need more DOF to reach there or there might be some collision between the links.