  Humans use tools to complete impact-aware tasks such as hammering a nail or
playing tennis. The postures adopted to use these tools can significantly
influence the performance of these tasks, where the force or velocity of the
hand holding a tool plays a crucial role. The underlying motion planning
challenge consists of grabbing the tool in preparation for the use of this tool
with an optimal body posture. Directional manipulability describes the
dexterity of force and velocity in a joint configuration along a specific
direction. In order to take directional manipulability and tool affordances
into account, we apply an optimal control method combining iterative linear
quadratic regulator(iLQR) with the alternating direction method of
multipliers(ADMM). Our approach considers the notion of tool affordances to
solve motion planning problems, by introducing a cost based on directional
velocity manipulability. The proposed approach is applied to impact tasks in
simulation and on a real 7-axis robot, specifically in a nail-hammering task
with the assistance of a pilot hole. Our comparison study demonstrates the
importance of maximizing directional manipulability in impact-aware tasks.
