  Recent advancements have enabled human-robot collaboration through physical
assistance and verbal guidance. However, limitations persist in coordinating
robots' physical motions and speech in response to real-time changes in human
behavior during collaborative contact tasks. We first derive principles from
analyzing physical therapists' movements and speech during patient exercises.
These principles are translated into control objectives to: 1) guide users
through trajectories, 2) control motion and speech pace to align completion
times with varying user cooperation, and 3) dynamically paraphrase speech along
the trajectory. We then propose a Language Controller that synchronizes motion
and speech, modulating both based on user cooperation. Experiments with 12
users show the Language Controller successfully aligns motion and speech
compared to baselines. This provides a framework for fluent human-robot
collaboration.
