[ros-users] Control system design question.

Konrad Banachowicz konradb3 at gmail.com
Fri Sep 17 10:12:23 UTC 2010

I'm working on integration of orocos RT-controller with ROS manipulation
I already done joint_state_publisher and oro_action_server. Next on my list
are joint_trajectory_action and JointSplineTrajectoryController.
I have some concerns about real-time behaviours of those, and way of
implementation in orocos.

joint_trajectory_action :
It receive goal containing trajectory (variable size, unbounded size), then
check constraints and send to JointSplineTrajectoryController.

It loop generating interpolated position for joint regulator.
When it receive new trajectory it reorder joints in received trajectory
(memory allocation, iterating on unknown size array) and try to compose
current trajectory with newly received (memory allocation, iterating on
unknown size array).
It have to by done between two sequential interpolations (in my system 1ms).

My solution :
Data transmited between  joint_trajectory_action and
JointSplineTrajectoryController contains only single point (constant size).

joint_trajectory_action do joint reordering and compose trajectories and is
feeding JointSplineTrajectoryController with trajectory points.

JointSplineTrajectoryController interpolate between two points (have one
point buffer)

This solution should work with trajectories when time between points is >>

What do you think about doing this this way ?
What is alternative solutions ?
What do you think about re-usability of this solution in yours systems ?

Konrad Banachowicz
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