Multidimensional Capacitive Sensing for Robot-Assisted Dressing and Bathing

Abstract

Robotic assistance presents an opportunity to benefit the lives of many people with physical disabilities, yet accurately sensing the human body and tracking human motion remain difficult for robots. We present a multidimensional capacitive sensing technique that estimates the local pose of a human limb in real time. A key benefit of this sensing method is that it can sense the limb through opaque materials, including fabrics and wet cloth. Our method uses a multielectrode capacitive sensor mounted to a robot's end effector. A neural network model estimates the position of the closest point on a person's limb and the orientation of the limb's central axis relative to the sensor's frame of reference. These pose estimates enable the robot to move its end effector with respect to the limb using feedback control. We demonstrate that a PR2 robot can use this approach with a custom six electrode capacitive sensor to assist with two activities of daily livingdressing and bathing. The robot pulled the sleeve of a hospital gown onto able-bodied participants' right arms, while tracking human motion. When assisting with bathing, the robot moved a soft wet washcloth to follow the contours of able-bodied participants' limbs, cleaning their surfaces. Overall, we found that multidimensional capacitive sensing presents a promising approach for robots to sense and track the human body during assistive tasks that require physical human-robot interaction.

Learning Grasping Points for Garment Manipulation in Robot-Assisted Dressing

“…Force information has been considered in [17] to adjust the robot motions to minimize the interaction force between the robot and the user. User movements have been tracked during the dressing process to plan the dressing trajectory in real-time [8,18]. While these different studies have led to promising results of dressing, they usually simplify the setup of their experiments by positioning the robot end-effector, with the garment manually attached on, close to the user's arm.…”

Proximity Perception in Human-Centered Robotics: A Survey on Sensing Systems and Applications

“…A smaller size is desirable for integration and spatial resolution but is attained at the cost of reduced electrode surface area, which limits the possible sensing range/sensitivity. A further interesting use-case for capacitive sensing is introduced by Erickson et al in [36], [37]. Using off-the-shelf electronics (MPR121 and the Teensy-board respectively), they implement a capacitive end-effector for the PR2 that is capable of detecting human limbs for dressing and washing tasks in health-care scenarios.…”

“…In [36], [37] Erickson et al apply the principles of reactive preshaping/contour following to the scenario of dressing and washing of patients. In [37], a 2×3 array on the end-effector is used to align the end-effectors distance and orientation to the patient's limbs, also following their contour.…”

“…In [36], [37] Erickson et al apply the principles of reactive preshaping/contour following to the scenario of dressing and washing of patients. In [37], a 2×3 array on the end-effector is used to align the end-effectors distance and orientation to the patient's limbs, also following their contour. They show this is a viable approach to automated caregiving tasks (dressing, washing), as visual occlusions are amortized and the detection of the human is reliable.…”

“…However, we think that the market for automated solutions in health care or service robotics based on proximity perception is there, especially in scenarios where the human is very close to the robot, preventing the sole use of cameras. In this survey, we discussed examples such as grasping of moving objects and handover [29], [66], [67], dressing and washing of patient [36], [37], or assistive robotics based on teleoperation [134], [133]. Overall, we think that medical and service robotics is a promising field for proximity perception, but more research is needed to establish use-cases and the corresponding methods before commercial exploitation appears on the horizon.…”