  Wrist-driven orthotics have been designed to assist people with C6-7 spinal
cord injury, however, the kinematic constraint imposed by such a control
strategy can impede mobility and lead to abnormal body motion. This study
characterizes body compensation using the novel Tenodesis Grasp Emulator, an
adaptor orthotic that allows for the investigation of tenodesis grasping in
subjects with unimpaired hand function. Subjects perform a series of
grasp-and-release tasks in order to compare normal (test control) and
constrained wrist-driven modes, showing significant compensation as a result of
the constraint. A motor-augmented mode is also compared against traditional
wrist-driven operation, to explore the potential role of hybrid human-robot
control. We find that both the passive wrist-driven and motor-augmented modes
fulfill different roles throughout various tasks tested. Thus, we conclude that
a flexible control scheme that can alter intervention based on the task at hand
holds the potential to reduce compensation in future work.
