Wrist Vibration Feedback to Improve Operator Awareness in Collaborative Robotics

Easy-to-use collaborative robotic solutions, where humans and robots share their skills, are becoming more and more popular in industrial applications. To improve human-robot collaboration, it is fundamental that the operator is aware of the robot status. Haptic feedback represents a promising way to convey robot intent, since the haptic perceptive channel is usually less overwhelmed than visive and auditive channel. Hence, it can be used to convey information on a background robot status in an unintrusive manner, especially when user’s attention is divided. In this paper, we propose to provide haptic feedback as vibration exerted to user’s wrist by a wearable device. To this end, we use a smartwatch, which is easy to program and not cumbersome to wear. We propose a haptic icon set consisting of different vibration patterns, each associated to different robot behaviors. Three experimental studies are set up to explore human ability to recognize such vibration patterns and assess their use in collaborative robotics, also in comparison with light notification. Results indicate that subjects perceive the proposed patterns as different: out of more than 1000 trials, vibration patterns are correctly identified by test participants in 87.4 % trials. Moreover, haptic feedback results advantageous in cooperative assembly, since it allows a reduction of 30 % of the total assembly time. Comparison with light feedback in a simulated industrial use case shows that vibration is more effective and appreciated by test participants, given its locatedness with the subject. However, test results also show that, when possible, vibration should be reinforced with visual feedback in order to further improve robot to human communication.