J-strips: Haptic joint limit warnings for human-robot interaction

The capabilities of humans and robots naturally compliment each other. Humans excel at spatial problem solving and fine manipulation tasks, whereas robots are good at supporting and stabilizing heavy loads. However, the typical impedance con- trol strategy employed in this domain does not communicate any of a robot's underlying physical constraints to its user. In this work, we propose j-strips, an anthromimetic haptic cue designed to convey stress in a robot manipulator to its human user. We hypothesize that when warned via j-strips that the robot is near- ing a joint limit in this way, the human user will modify the path of the robot to avoid the limit. We present the results of a pi- lot study of three human subjects manipulating a robot arm that uses j-strips to warn its user when its elbow position limit is ap- proached. Two of the subjects were found to significantly modify the manner in which they manipulated the robot, and both ver- bally reported that j-strips conveyed the intended message.