  In this paper we show how different choices regarding compliance affect a
dual-arm assembly task. In addition, we present how the compliance parameters
can be learned from a human demonstration. Compliant motions can be used in
assembly tasks to mitigate pose errors originating from, for example,
inaccurate grasping. We present analytical background and accompanying
experimental results on how to choose the center of compliance to enhance the
convergence region of an alignment task. Then we present the possible ways of
choosing the compliant axes for accomplishing alignment in a scenario where
orientation error is present. We show that an earlier presented Learning from
Demonstration method can be used to learn motion and compliance parameters of
an impedance controller for both manipulators. The learning requires a human
demonstration with a single teleoperated manipulator only, easing the execution
of demonstration and enabling usage of manipulators at difficult locations as
well. Finally, we experimentally verify our claim that having both manipulators
compliant in both rotation and translation can accomplish the alignment task
with less total joint motions and in shorter time than moving one manipulator
only. In addition, we show that the learning method produces the parameters
that achieve the best results in our experiments.
