Jack,
I say degrees here because the hardware command to the robot works this way. You must specify to the robot it's maximum tilt angle, in degrees, with a hardware configuration command (which will be available as a param or service call, soon).
The -1 to 1 value of the linear.x or linear.y then acts as a scaling factor, that is, it specifies the percent of the maximum tilt that should be applied to the hardware, thus affecting the speed.
I thought it was important to make known what the commands were actually telling the hardware to do, since this will vary on a per-configuration basis. Maybe a better way to say it is percentage of maximum tilt angle, which could then be interpreted in radians or degrees, knowing the configuration of the robot (which is set and reported in degrees at the hardware level).
Data published by the driver (when it gets there) will conform to all standards and be specified in radians.
Thanks for the insight,
Nate Roney
On Sat, Oct 16, 2010 at 09:30, Jack O'Quin
<jack.oquin@gmail.com> wrote:
Nate,
This looks like a cool device, definitely interesting for robotics
work. Thanks for making a ROS package.
On Sat, Oct 16, 2010 at 9:02 AM, Nate Roney <
nateroney@gmail.com> wrote:
>
> The units are degrees for the forward/backward and left/right tilt. These
> control the percentage of the maximum tilt (which is currently 30 degrees).
> Obviously, the more tilt, the faster it goes. I've found that anything more
> than 25 degrees actually drives the drone to the ground, so I'm thinking of
> adding a limit, and/or adding a rosparam allowing the change of the max
> angle.
http://www.ros.org/reps/rep-0103.html#units
As noted, there can be exceptions, domains where the default
conventions are not appropriate. We should not be pedantic about it. A
recent example came up with the GPS message discussion. Latitude and
longitude should be expressed in degrees, not in radians.
I made some similar mistakes in a couple of our autonomous vehicle
messages [[http://www.ros.org/wiki/art_msgs]]. I now wish I'd gotten
them right to begin with. The standards were not so clearly spelled
out back then. In my experience, it is a lot of extra work to change
messages later (more due to bag migration than to fixing all the
references).
Regards,
--