Symmetry modes and stiffnesses for bimanual rehabilitation

Bimanual rehabilitation devices show promise for use in low cost trainers for home use. To gain a better understanding of the symmetry modes and coupling stiffnesses that would be beneficial for home use bimanual trainers, we conducted a haptic tracking task. Participants used one hand to recreate the trajectory applied by a robot to the other hand using three bimanual symmetry modes. The participants recreated visual symmetry and joint space (mirror) symmetry more easily than point mirror symmetry. Joint space symmetry was the easiest mode when the trajectory was an increasing chirp frequency function. The stiffness between the robot and one hand affected the coordination between both hands and stiffnesses of 200-700 N/m enabled better tracking than 50 N/m.