We are investigating how people perceive forces in a variety of contexts, and how these forces can be used for conveying information to a person. One way we do this is by using joint torques transmitted by a light-weight exoskeleton to gently push a wearer's arm toward a desired position or through a desired trajectory. An initial demo of the system with an elbow exoskeleton is shown in the video below. A direct-drive elbow exoskeleton guides the wearer's arm by providing small (less than 1Nm) torques. Since the exoskeleton is powered by a large-diameter motor with no gearbox, there are essentially zero parasitic torques. The exoskeleton seen in the video weighs around 500 grams (~1 pound).
A first look at the torque magnitudes needed to be noticed by a person are described in our paper "Just Noticeable Differences for Joint Torque Feedback During Static Poses" by Hubert Kim, Hongxu Guo, and Alan Asbeck, in the IEEE Int. Conf. on Robotics and Automation (ICRA), May 2020 (Link), and a description of the arm exoskeleton is in "An elbow exoskeleton for haptic feedback made with a direct drive hobby motor" by Hubert Kim and Alan Asbeck in HardwareX, 8, e00153, 2020 (Link).
We are also looking at how people perceive forces in virtual reality.