Acceleration limits

[efernandez]

No description provided.

[po1]

A bit of explanation: this patch changes where the acceleration limit enforcer gets the current velocity.
To this point, a call to getVelocity() was made, which can only be successful if the joint provides velocity feedback.
This feedback is not always available. So the proposal here is to change the behavior of the interface to keep the last velocity command in memory instead of querying the joint for its current velocity.

Now my comments:

• the previous behavior was broken, as it assumed that velocity feedback was available, even when it is not. The new behavior works in both cases, but might not work as good as the old behavior when there is velocity feedback.
• maybe there should be a mechanism to be able to tell if velocity feedback is available, and to provide with the last known velocity command if there is none, as a backup behavior.

[po1]

@adolfo-rt

[adolfo-rt]

See issue #3 for pending tasks in this respect.