  Hand synergies, or joint coordination patterns, have become an effective tool
for achieving versatile robotic grasping with simple hands or planning
algorithms. Here we propose a method to determine the hand synergies such that
they can be physically implemented in an underactuated fashion. Given a
kinematic hand model and a set of desired grasps, our algorithm optimizes a
Mechanically Realizable Manifold designed to be achievable by a physical
underactuation mechanism, enabling the resulting hand to achieve the desired
grasps with few actuators. Furthermore, in contrast to existing methods for
determining synergies which are only concerned with hand posture, our method
explicitly optimizes the stability of the target grasps. We implement this
method in the design of a three-finger single-actuator hand as an example, and
evaluate its effectiveness numerically and experimentally.
