Title: 3D Human Pose Estimation on a Configurable Bed from a Pressure Image,
Abstract: Robots have the potential to assist people in bed, such as in healthcare
settings, yet bedding materials like sheets and blankets can make observation
of the human body difficult for robots. A pressure-sensing mat on a bed can
provide pressure images that are relatively insensitive to bedding materials.
However, prior work on estimating human pose from pressure images has been
restricted to 2D pose estimates and flat beds. In this work, we present two
convolutional neural networks to estimate the 3D joint positions of a person in
a configurable bed from a single pressure image. The first network directly
outputs 3D joint positions, while the second outputs a kinematic model that
includes estimated joint angles and limb lengths. We evaluated our networks on
data from 17 human participants with two bed configurations: supine and seated.
Our networks achieved a mean joint position error of 77 mm when tested with
data from people outside the training set, outperforming several baselines. We
also present a simple mechanical model that provides insight into ambiguity
associated with limbs raised off of the pressure mat, and demonstrate that
Monte Carlo dropout can be used to estimate pose confidence in these
situations. Finally, we provide a demonstration in which a mobile manipulator
uses our network's estimated kinematic model to reach a location on a person's
body in spite of the person being seated in a bed and covered by a blanket.