[cob_teleop] cob_teleop_keyboard publish behavior

[fmessmer]

This is nothing too serious as the node is not frequently used...still, as I stumbled over it yesterday, I wanted it to be documented:

The following plot shows the publishing behavior when a key is kept pressed:

In particular, it can be seen in the trangle_down marker on the yellow curve when the first event is received by the teleop_keyboard node and the first twist is published. This first twist message make the velocity_smoother (purple curve) start to "fade-in".
However, as the next event of the teleop_keyboard node (triangle_down) is received much later, the velocity_smoother already starts to "fade-out" as it thinks that no more command is coming....
Then after that second event each following event arrives at a much higher rate....
This behavior can be observed when simply pressing a key on the keyboard and hold it down....first one character is shown.....then (after few ms) the following characters come rushing......

@fmessmer FYI

[fmessmer]

not planned