The wouse: A wearable wince detector to stop assistive robots

Persons with severe motor impairments depend heavily upon caregivers for the performance of everyday tasks. Ongoing work is exploring the potential of giving motor-impaired users control of semi-autonomous assistive mobile manipulators to enable them to perform some self-care tasks such as scratching or shaving. Because these users are less able to escape a robot malfunction, or operate a traditional run-stop, physical human-robot interaction poses safety risks. We review approaches to safety in assistive robotics with a focus on accessible run-stops, and propose wincing as an accessible gesture for activating a run-stop device. We also present the wouse, a novel device for detecting wincing from skin movement near the eye, consisting of optical mouse components mounted near a user's temple via safety goggles. Using this device, we demonstrate a complete system to run-stop a Willow Garage PR2 robot, and perform two preliminary user studies. The first study examines discrimination of wincing from self-produced facial expressions. The results indicate the possibility for discrimination, though variability between users and inconsistent detection of skin movement remain significant challenges. The second experiment examines discrimination of wincing from external mechanical manipulations of the face during self-care tasks. The results indicate that the wouse, using a classifier trained with data from the first experiment, can be used during face-manipulation tasks. The device produced no false positives, but succeeded in correctly identifying wincing events in only two of four subjects.