[ros-users] configuring laser_tilt_controller

[Vijay Pradeep]

Hi Dejan,

Assuming that you're running with a fairly standard PR2 configuration, the
laser controller that you're running is documented here:
http://www.ros.org/wiki/pr2_mechanism_controllers/LaserScannerTrajController

The* set_periodic_cmd *service call can execute only a subset of the
profiles that are possible with *set_traj_cmd*.  *set_periodic_cmd *can only
do triangle wave profiles where the laser moves the same speed on both the
up and down sweep.

The *set_traj_cmd* lets you specify all the timepoints of the trajectory,
giving much more flexibility.

Suppose you have a periodic command with period=4, amplitude=2, and
offset=1.  The equivalent trajectory command would have the following
timepoints:
time_from_start=0, pos=3
time_from_start=2, pos=-1
time_from_start=4, pos=3

Hopefully this helps!
Vijay

On Sat, Sep 11, 2010 at 3:31 PM, Dejan Pangercic
<dejan.pangercic at gmail.com>wrote:

> Hi there,
> I noticed that there are 2 ways to configure laser_tilt_controller,
> one with pr2_msgs/LaserTrajCmd (as in e.g. pr2_move_base,
> pr2_move_base.py) message and
> second with a pr2_msgs/PeriodicCmd (as in e.g. send_periodic_cmd.py).
> What is the actual difference? Can one somehow find the mapping
> between
> their values?
>
> I have a case where I drive(using pr2_2dnav) around with the PR2, halt
> at the certain locations and map the environment. The tilting rate at
> mapping has to of course be significantly  slower that the one needed
> by the "pr2_2dnav" application which requires constant back-and-forth
> reconfiguration. So far my preferred method of configuring the
> laser_tilt_controller was by using the send_periodic_cmd.py program
> but then I do not seem to be able to hit the same configuration as
> done by the  "pr2_2dnav" which consequentially results in sloppy
> performance by the latter.
> So if the mapping between both messages is possible I'd be
> tremendously glad to learn about.
>
> thx and cheers, D.
>
> --
> MSc. Dejan Pangercic
> PhD Student/Researcher
> Intelligent Autonomous Systems Group
> Technische Universität München
> Telephone: +49 (89) 289-26908
> E-Mail: dejan.pangercic at cs.tum.edu
> WWW: http://ias.cs.tum.edu/people/pangercic
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>



-- 
Vijay Pradeep
Systems Engineer
Willow Garage, Inc.
 <tfoote at willowgarage.com>vpradeep at willowgarage.com
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