  Bimanual object manipulation involves multiple visuo-haptic sensory feedbacks
arising from the interaction with the environment that are managed from the
central nervous system and consequently translated in motor commands. Kinematic
strategies that occur during bimanual coupled tasks are still a scientific
debate despite modern advances in haptics and robotics. Current technologies
may have the potential to provide realistic scenarios involving the entire
upper limb extremities during multi-joint movements but are not yet exploited
to their full potential. The present study explores how hands dynamically
interact when manipulating a shared object through the use of two
impedance-controlled exoskeletons programmed to simulate bimanually coupled
manipulation of virtual objects. We enrolled twenty-six participants (2 groups:
right-handed and left-handed) who were requested to use both hands to grab
simulated objects across the robot workspace and place them in specific
locations. The virtual objects were rendered with different dynamic proprieties
and textures influencing the manipulation strategies to complete the tasks.
Results revealed that the roles of hands are related to the movement direction,
the haptic features, and the handedness preference. Outcomes suggested that the
haptic feedback affects bimanual strategies depending on the movement
direction. However, left-handers show better control of the force applied
between the two hands, probably due to environmental pressures for right-handed
manipulations.
