Whole-arm tactile sensing for beneficial and acceptable contact during robotic assistance

Abstract

Many assistive tasks involve manipulation near the care-receiver's body, including self-care tasks such as dressing, feeding, and personal hygiene. A robot can provide assistance with these tasks by moving its end effector to poses near the care-receiver's body. However, perceiving and maneuvering around the care-receiver's body can be challenging due to a variety of issues, including convoluted geometry, compliant materials, body motion, hidden surfaces, and the object upon which the body is resting (e.g., a wheelchair or bed). Using geometric simulations, we first show that an assistive robot can achieve a much larger percentage of end-effector poses near the care-receiver's body if its arm is allowed to make contact. Second, we present a novel system with a custom controller and whole-arm tactile sensor array that enables a Willow Garage PR2 to regulate contact forces across its entire arm while moving its end effector to a commanded pose. We then describe tests with two people with motor impairments, one of whom used the system to grasp and pull a blanket over himself and to grab a cloth and wipe his face, all while in bed at his home. Finally, we describe a study with eight able-bodied users in which they used the system to place objects near their bodies. On average, users perceived the system to be safe and comfortable, even though substantial contact occurred between the robot's arm and the user's body.

Task-centric selection of robot and environment initial configurations for assistive tasks

“…In addition, all tasks in this work were defined with full 6-DoF goal poses, although some tasks, such as sponge baths, have position requirements and few orientation requirements. In this work we assume tasks must be performed collision-free, but in [2], we found that contact is both allowable and useful for increasing the workspace in assistive tasks. We also did not address tasks with complex motions like dressing, or tasks with high strength requirements like lifting or ambulating.…”

“…The equation for kinematic isotropy is shown in equation (2). ∆(q i ) is the kinematic isotropy for the arm in joint configuration q i .…”

“…Selecting a good initial configuration can be challenging and has been addressed in many ways. In our previous work, we have selected start locations for the robot manually with trial and error [1], [2], or have used data-driven approaches using robot-centric success likelihood [3]. In this work we take a different approach: we present Task-centric initial Configuration Selection (TCS) (see Figure 1).…”

In-home and remote use of robotic body surrogates by people with profound motor deficits

“…We modified a standard PR2 6/43 by adding dense foam padding around the metal grippers and the mobile base of the robot to reduce potential negative consequences of contact. We also added fabric-based tactile sensing skin [36,37] around the mobile base and to both upper arms and forearms ( Fig. 1B,C).…”

Material Recognition from Heat Transfer given Varying Initial Conditions and Short-Duration Contact

“…For example, a robot reaching into a densely cluttered environment can use tactile sensing across its arm to better maneuver within the environment and map it [1,2]. Likewise, an assistive robot reaching around a person with disabilities could potentially use tactile sensing to recognize contact between its arm and the person's body or wheelchair [3]. Similarly, tactile sensing across a robot's fingers might provide useful information during in-hand manipulation.…”