ANRO summer school

h1. Lab 4: Interpolation of motion

h2. Scope:

This laboratory consist of two parts:

* A short introduction.

* Writing your own ROS package.

h2. The task:

* Develop the system from the previous laboratory by either copying the package or modyfying it.

* Create ROS node jint that interpolates trajectory in configuration space.

  * The node uses ROS service (Remote Procedure Call - RPC) of type jint_control_srv. You should create this service type.

    * The node jint gets desired joint position and other required parameters (e.g. duration) as input.

    * The node answers interpolation status that can be sent after the interpolation is complete or immediately, if there are errors in the input parameters (e.g. zero or negative duration).

  * The RPC can be executed directly from terminal or by a dedicated node jcmd.

  * After reception of valid command, the node jint publishes interpolated positions on ROS topic and sends it to robot_state_publiher node.

    * At first, use linear interpolation.

    * Next, add more sophisticated method, e.g. trapezoid velocity profile or spline interpolation (please refer to: https://en.wikipedia.org/wiki/Spline_interpolation#Algorithm_to_find_the_interpolating_cubic_spline). You can assume zero velocity at the beginning and at the end of motion.

    * All interpolation modes should be implemented in one ROS node and can be selected in jint_control_srv.

  * Visualize behaviour of the system in RVIZ. Visualize the followed trajectory.

  !lab4-scheme-a.png!

* Create a similar ROS node oint, that generates interpolation of a reference frame in Cartesian space.

  * In this task the frame is not related to the robot nor to its end effector.

  * Use *pose* marker in RVIZ and set its shape as axes.

  * The message sent to RVIZ is of type PoseStamped from geometry_msgs package.

  * At first, interpolate position only and keep orientation constant.

  * Next, interpolate orientation.

  * The command for node oint is sent through ROS service of type oint_control_srv from terminal or from a dedicated node ocmd.

  * Visualize behavior of the system in RVIZ. Draw the trajectory of the frame.

  !lab4-scheme-b.png!

* Add wiki page to your repository (the documentation). The page should contain description of source files, instruction for launching and description of tests.

  * On all graphs of structure of the system topics and services should be shown differently.

  * The plots of variables from topics should contain outputs of interpolators. The outputs should be continuous.

* Use separate roslaunch files for:

  * roscore and RVIZ (it should be running until URDF file is modified).

  * The rest of the system.

* Test the system and show it to the tutor.