  Ergonomics and human comfort are essential concerns in physical human-robot
interaction. Common practical methods in the area either fail in estimating the
correct posture due to occlusion or suffer from inaccurate ergonomics models in
performing postural optimization. We propose a novel alternative framework for
posture estimation, assessment, and optimization for ergonomically intelligent
physical human-robot interaction. We show that we can estimate human posture
solely from the trajectory of the interacting robot with median deviation of 5
deg from motion capture. We propose DULA, a differentiable ergonomics
assessment tool with 99.73% accuracy comparing to RULA. We use DULA in postural
optimization for physical human-robot interaction tasks such as co-manipulation
and teleoperation. We evaluate our framework through human and simulation
experiments.
