[ros-users] Fuerte SIG 2.10: Efficient Simulation/Control of Articulated Robots

[Herman Bruyninckx]

On Wed, 14 Sep 2011, Mike Stilman wrote:

> Dear ROS Users,
>
> In a continued effort to contribute robust and useful tools to the ROS
> community, please check out ROS Fuerte Planning SIG 2.10. and consider
> joining the effort if you agree that it will be valuable to the community.
>
> SIG 2.10: Efficient Simulation and Control of Articulated Robots
> ----------------------------------------------------------------
> The goal is to develop and integrate a unified dynamic simulation/control
> infrastructure with efficient representation, efficient computation of
> articulated body dynamics in generalized coordinates, contact handling and
> its link to planning, trajectory generation and rapid motion.
>
> Currently ROS users link numerous data structures and packages to achieve
> dynamic simulation for control and controller validation. For instance,
> URDF data structures are copied to KDL ones to use kinematic solvers and
> then again to ODE or Bullet for dynamic simulation and contact resolution.
> This can be computationally inefficient and difficult to master for
> end-users. Furthermore, the use of ODE/Bullet for articulated body
> simulation can also cause instability and inefficiency. These simulators
> are designed to handle individual bodies with iterative (penalty)
> resolution of constraints. This SIG would focus on the development of a
> single data structure that can handle arbitrary rigid and articulated
> bodies through featherstone-like dynamics solvers for handling articulated
> dynamics in generalized (minimal) coordinates.

KDL has already some of these, and more are coming. So, instead of starting
yet another library, why not improve what KDL has already?

We are now working on a hybrid dynamics solver, which goes a step further
than the traditional Featherstone-based algorithms, in that partial
acceleration constraints can be taken into account in linear time.

> We also aim to have the SIG consider broadening the library with a suite
> of algorithms based on forward and inverse kinematics and dynamics such as
> robot control, animation and planning.
>
> Prof. Karen Liu and I of the Graphics and Humanoid Robotics Labs at GT are
> already well into the development of a data structure and simulator that
> satisfies these needs. The missing link was collision detection and
> conveniently, Jia Pan, Sachin and Dinesh Manocha have just created an
> efficient BSD collision detection library in ROS! We are now using this
> library to implement LCP-based contact handling which will complete the
> first beta of the new simulator to be released open source (BSD) to the
> ROS community in a few weeks.
>
> The goal of this SIG would be to jointly develop this library, integrate
> it with Gazebo simulation as well as motion planners, controllers and
> optimal motion generation algorithms. We think this will be a fantastic
> resource that will spur collaboration between different groups that
> require a single highly efficient solution to robot kinematics and
> dynamics including contact between robots, objects and enviroments.

I hope that your vision on "integration" means that you keep the algorithms
as separate and independent as possible, and try to find consensus on how
to compose them. For example, adding collision information to a dynamics
algorithm in order to do, for example, force or impedance control, should
not be done by extending the dynamics algorithm with collision data
structures, but via the external force or Cartesian (velocity,
acceleration) constraints, in combination with a contact dynamics impedance
model.

> If you are interested, please shoot us an email:
> (mstilman at cc.gatech.edu, karenliu at cc.gatech.edu)

Post here, read here! :-)

> And sign up for SIG 2.10 at:
> http://www.ros.org/wiki/fuerte/Planning
>
> Best,
>
> Mike

Herman

> ---------------------------------
> Mike Stilman
> Assistant Professor
> Director: Humanoid Robotics Lab
> Robotics and Intelligent Machines
> Georgia Institute of Technology
> ---------------------------------
> email: mstilman at cc.gatech.edu
> cell:  (650)283-4284
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-- 
--
   K.U.Leuven, Mechanical Eng., Mechatronics & Robotics Research Group
     <http://people.mech.kuleuven.be/~bruyninc> Tel: +32 16 328056
   EURON Coordinator (European Robotics Research Network) <http://www.euron.org>
   Open Realtime Control Services <http://www.orocos.org>
   Associate Editor JOSER <http://www.joser.org>, IJRR <http://www.ijrr.org>