  Accurate post-impact velocity predictions are essential in developing
impact-aware manipulation strategies for robots, where contacts are
intentionally established at non-zero speed mimicking human manipulation
abilities in dynamic grasping and pushing of objects. Starting from the
recorded dynamic response of a 7DOF torque-controlled robot that intentionally
impacts a rigid surface, we investigate the possibility and accuracy of
predicting the post-impact robot velocity from the pre-impact velocity and
impact configuration. The velocity prediction is obtained by means of an impact
map, derived using the framework of nonsmooth mechanics, that makes use of the
known rigid-body robot model and the assumption of a frictionless inelastic
impact.The main contribution is proposing a methodology that allows for a
meaningful quantitative comparison between the recorded post-impact data, that
exhibits a damped oscillatory response after the impact, and the post-impact
velocity prediction derived via the readily available rigid-body robot model,
that presents no oscillations and that is the one typically obtained via
mainstream robot simulator software. The results of this new approach are
promising in terms of prediction accuracy and thus relevant for the growing
field of impact-aware robot control. The recorded impact data (18 experiments)
is made publicly available, together with the numerical routines employed to
generate the quantitative comparison, to further stimulate interest/research in
this field.
