  Multi-stage forceful manipulation tasks, such as twisting a nut on a bolt,
require reasoning over interlocking constraints over discrete as well as
continuous choices. The robot must choose a sequence of discrete actions, or
strategy, such as whether to pick up an object, and the continuous parameters
of each of those actions, such as how to grasp the object. In forceful
manipulation tasks, the force requirements substantially impact the choices of
both strategy and parameters. To enable planning and executing forceful
manipulation, we augment an existing task and motion planner with controllers
that exert wrenches and constraints that explicitly consider torque and
frictional limits. In two domains, opening a childproof bottle and twisting a
nut, we demonstrate how the system considers a combinatorial number of
strategies and how choosing actions that are robust to parameter variations
impacts the choice of strategy.
