Muscle-propelled force feedback

Abstract

Force feedback devices resist miniaturization, because they require physical motors and mechanics. We propose mobile force feedback by eliminating motors and instead actuating the user's muscles using electrical stimulation. Without the motors, we obtain substantially smaller and more energy-efficient devices. We present a prototype that fits on the back of a mobile phone. It actuates users' forearm muscles via four electrodes, which causes users' muscles to contract involuntarily, so that they tilt the device sideways. As users resist this motion using their other arm, they perceive force feedback. We demonstrate the interaction at the example of an interactive videogame in which users steer an airplane through winds rendered using force feedback. In a first user study, we found our device to cause users to produce up to 18.7N of force, when used to actuate their palm flexors. In a second study, participants played the video game de-scribed above; all ten participants reported to prefer the experience of muscle-propelled force feedback to vibrotactile feedback.