[ros-users] Sonar sensor and PTZ actuators on Erratic

[Eric Perko]

2010/12/20 Pablo Iñigo Blasco <pibgeus at gmail.com>

> Hi Brian, Anton and ROS community.
>
> Our group is working with erratic robots. As we talked<http://ros-users.122217.n3.nabble.com/erratic-player-vs-ua-erratic-player-td768165.html>the ua_erratic_player package is the current official erratic package. So
> we've been working with it for a while. However it has some lacks, e.g. we
> can't read sonar sensor values and we can't use neither the vision-ptz
> actuator nor the ranger-tilt-actuator.
>
> Given that the node implementation uses the player framework it's
> relatively easy to extend it and add such functionality. We did it but now
> we have got some doubts about how the design the erratic-node interface
> following ROS conventions:
>
> - There isn't a standard sonar array message (like e.g. LaserScan.msg), is
> it? Such kind of message may not have sense since sonar array may not be
> considered a device itself and it usually has a custom arrangement. e.g. The
> erratic robot has 8 sonar sensors but they aren't regularly arranged (in the
> same way as laserscans are: angle_min,angle_mas,angle_increment,etc). In the
> other hand 8 topics of type (Header/float) don't look a good solution. We're
> planning to extend the erratic urdf by adding the sonar devices frames and
> creating a message like this:
> Header
> string[] frames
> float[] ranges
>

There is actually a standardized message for a sonar.

http://www.ros.org/doc/api/sensor_msgs/html/msg/Range.html

Should be available in unstable and Diamondback once it's released.

See
http://www.ros.org/wiki/sensor_msgs/Reviews/2010-10-04_Ranger_Proposal_API_Review
for
how we envisioned using that message to send out a "RangeArray". Basically,
individual Range message for each sonar, letting tf handle the fact that
they have different orientations and locations.

- Eric


>
> - Regarding the vision-ptz actuator. What would be a good way to send
> commands? JointArray + robot_state_publisher? Maybe a look_at command topic
> of type Point3D??
> - For the ranger-tilt actuator I guess is better a topic of type
> (Header/float).
>
> What do you think about this? Suggestion, correction or Ideas are welcome.
>
> Thanks in advance.
> Regards.
>
> --
> Pablo Iñigo Blasco.
> Computer Architecture Department. Universidad de Sevilla (Spain)
> http://es.linkedin.com/in/pibgeus | http://geus.wordpress.com
>
>
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