Kinematic Compatibility of a Wrist Robot With Cable Differential Actuation: Effects of Misalignment Compensation via Passive Joints

We present the UDiffWrist (UDW), a low-impedance 2-DOF wrist exoskeleton featuring cable-differential transmission. To investigate effect of different design strategies for achieving kinematic compatibility, we developed two versions this robot: One version (UDW-C) achieves compatibility only in case perfect alignment between human and robot joints. The second (UDW-NC) connects via passive joints to achieve regardless Through characterization experiments, found that UDW-NC was more robust misalignments than UDW-C: increase maximum interaction torque associated with greater UDW-C (p = 0.003). However, displayed Coulomb friction < 0.001). Further, increased presence axes also transfer accurate UDW-NC. These results suggest small (10 deg) movements considered, advantages terms are likely overshadowed by negative effects accuracy.