Trace:

Differences

This shows you the differences between two versions of the page.

--- projects:sandbox_ingo [2011/11/14 21:42] – created kresse
+++ projects:sandbox_ingo [2013/04/15 14:27] (current) – ... kresse
@@ Line 1: / Line 1: @@
+====== Ingo's ROS code sandbox ======
+You can check out my public Mercurial repository with:
+  hg clone http://toychest.in.tum.de/users/kresse/sandbox
+**NOTE**: The relevant code is being moved to github and bitbucket. Stay tuned.
+{{ :projects:pr2_pancake_pushing.png?300|Constraint specification for pancake-pushing}}
+Among other stuff it contains:
+  * a system for constraint based task description:
+    * specify constraints between two objects like height, distance, align, ...
+    * specify a range of allowed values for each constraint
+    * orocos realtime component (based on iTaSC)
+    * python executive, sending ROS messages to that component
+    * a visualization of constraints for rviz, using the task jacobian
+  * a visualization of twists for rviz
+  * a pretty general joystick-to-twist converter
+  * a little tool that makes your speaker (or soundcard) beep tunes from ROS.
+-----
+==== Console Interface for feature_constraint_controller ===
+command line script 'state' in feature_constraints_utils.
+  * ''state get'' : Print the current values of chi, chi_des, joint_angles, tool_pose and object_pose in the form: <code>
+chi:
+.1 2.2 -4.44 ...
+joints:
+2 3
+...
+</code> For clarity, the number of decimal digits are limited to 3 and can be set using the rosparam ''~digits''.
+  * ''state get //item//'': Print ''//item//'' in a single line, where ''//item//'' is one of chi, chi_des, joint_angles, tool_pose and object_pose.
+  * ''state set angles //angles//''
+  * ''state set chi //chi-angles//''
+  * ''state set chi -'' : (repeatedly) get values from stdin
+The semantics of ''//chi-angles//'' is as follows: A numeric values translates
+into a small range around this value, a string becomes 'not important' and sets
+the respective weight to zero. The command ''state set angles'' only accepts
+numeric values.
+  * ''state reset'' : Stop all feature controllers and resets the arm angles to default values, stored in the rosparam: ''/loopback_controllers/joints''.
+  * ''state prefix'' : Get the current feature controller name which is used as a prefix in topic names.
+  * ''state prefix //name//'' : Set the prefix. This name is stored in the rosparam '' '/constraint_controller' ''.
+  * ''state prefixes'' : Search topic names and display potential prefixes.
+-----
+Slightly different approach: A rosparam interface.
+  * state get yaml >file.xml : ouputs the yaml in a format that can be loaded with rosparam load.
+  * ''state get param ///param_name//'' : directly saves the state into /param_name
+  * ''state set chi ///param_name/chi//''
+  * ...
+Nothing speaks against supporting both interfaces.
+Why not:
+  * ''state set _chi:=///param_name/chi//'' ?
+This would be too error-prone to use since the value of /state/chi (which is only a name) would stay on the param server and would influence the next call to ''state''. Contrary to ROS conventions, ''state'' would have to delete this parameter after reading it.
+-----
+**NOTES**:
+  * Joint angles and poses are taken from ''/tf'' and ''/joint_states''.
+  * The interface to the feature constraint controller is defined by it's name prefix and the topics <prefix>/constraint_config, <prefix>/constraint_command and <prefix>/constraint_state.
+  * When no prefix is specified, the first feature controller that is found is used.
+  * Joint angle names are are recovered from the URDF using the package 'urdf_parser_py', using the name of the first and last joint which in turn is taken from the constraint_controller parameters. A fallback for PR2 and Rosie arm joint names is built in, for the case that 'urdf_parser_py' is missing.
+-----
+**TODO**:
+  * When talking to two feature constraint controllers, prefixes must be switched all the time. Supporting an environment variable should be more convenient.
+  * (Future): What shall we do if two arms and/or several constraint sets are active in the same controller? Give names to arms and constraint sets and use these names with every invocation of ''state''? Have a rosparam, that holds the default name, for convenience? This also becomes important when implementing multi-robot functionality.