Dynamic simulation and experimental validation of an upper extremity powered orthosis

The Wilmington Robotic Exoskeleton (WREX) is a passive upper limb orthosis powered by elastic bands, designed to assist children with weakness in their upper limbs. Patient studies with the WREX have determined that an external power source would enhance performance of the system. Two actuation schemes were considered: (i) motors in series with springs at the joints, called `Torsional´ (ii) motors in series with gravity balancing elastic bands, called `In-line´. Dynamic models of these two motor placements were developed. Dynamic simulations, based on representative patient motion data, were performed. We observed that the torsional case with motors in series with springs at the joints required substantially less torque when compared to the in-line case with motors in series with gravity balancing springs. An experimental platform is being developed with this configuration and preliminary results are included.