Add Bumper.msg or ContactState.msg

[efernandez]

I wonder why the sensor_msgs don't include a message for bumpers, with header and a boolean (is_pressed).

In gazebo_msgs there's a ContactState.msg that might be used for this purpose, but it looks overcomplicated for a bumper that just has two states.

Since it's common to have bumpers in a robot, IMHO there should be a msg to represent them; indeed, there are even messages for Temperature and RelativeHumidity.

[tfoote]

If you'd like to propose one and put it up for review we can definitely do that. Some past examples are here: http://wiki.ros.org/common_msgs/Reviews or http://wiki.ros.org/sensor_msgs/Reviews

Some things off the top of my head which complicate bumper messages are that many are not binary, are sometimes directional, are rarely a single point, and most move when touched, and some have different trigger thresholds. Understanding the set of use cases which it is expected to cover vs not expected to cover is important. And if the use cases are not generic enough it might not be worth creating a common message if most users will need to create a custom variation anyway to create a self describing message.

[po1]

I would also like a message that could be used for any binary sensor, button, switch...
Something like Contact or Switch. I agree that non-binary bumpers exist and are used, and they should probably use a more complicated and generic message. But simple binary cases are also quite usual IMO.
We currently have a standalone package just for such a message, which adds complexity and time to our builds for very little benefit.

[efernandez]

To be more specific, in gazebo_msgs the bumper is defined by the ContactState.msg, which is used and published in the corresponding gazebo_ros_bumper plugin in gazebo_plugins.

gazebo_msgs/msg$ cat ContactState.msg 
string info                                   # text info on this contact
string collision1_name                        # name of contact collision1
string collision2_name                        # name of contact collision2
geometry_msgs/Wrench[] wrenches               # list of forces/torques
geometry_msgs/Wrench total_wrench             # sum of forces/torques in every DOF
geometry_msgs/Vector3[] contact_positions     # list of contact position
geometry_msgs/Vector3[] contact_normals       # list of contact normals
float64[] depths                              # list of penetration depths

On the contrary, a simple bumper can be like this:

Header header
bool is_pressed

which also includes the header.

Honestly, I don't now exactly how to set something as simple as binary-state bumper in the ContactState msg, which looks like an overkill anyway.

[tfoote]

There's a thread started here: https://groups.google.com/forum/#!topic/ros-sig-drivers/9p4oeXFgF-o

[tfoote]

Closing this due to no activity.

[EwingKang]

It's a shame that the discussion died. A simple contact switch/ limit switch is definitely everywhere in the robotic system. Truly hope someone can add this simple feature.