  Closed kinematic chains are created whenever multiple robot arms concurrently
manipulate a single object. The closed-chain constraint, when coupled with
robot joint limits, dramatically changes the connectivity of the configuration
space. We propose a regrasping move, termed "IK-switch", which allows
efficiently bridging components of the configuration space that are otherwise
mutually disconnected. This move, combined with several other developments,
such as a method to stabilize the manipulated object using the environment, a
new tree structure, and a compliant control scheme, enables us to address
complex closed-chain manipulation tasks, such as flipping a chair frame, which
is otherwise impossible to realize using existing multi-arm planning methods.
