  The transition from free motion to contact is a challenging problem in
robotics, in part due to its hybrid nature. Additionally, disregarding the
effects of impacts at the motion planning level often results in intractable
impulsive contact forces. In this paper, we introduce an impact-aware
multi-mode trajectory optimization (TO) method that combines hybrid dynamics
and hybrid control in a coherent fashion. A key concept is the incorporation of
an explicit contact force transmission model in the TO method. This allows the
simultaneous optimization of the contact forces, contact timings, continuous
motion trajectories and compliance, while satisfying task constraints. We
compare our method against standard compliance control and an impact-agnostic
TO method in physical simulations. Further, we experimentally validate the
proposed method with a robot manipulator on the task of halting a
large-momentum object.
