Fig. 1.
Exoskeleton emulator and study protocol. (a) Representative setup of the ankle exoskeleton testing platform for evaluating rotational stiffness plantarflexion assistance. The exoskeleton provided plantarflexion torque to the bilateral ankle end-effectors through off-board motors. The controller emulated elastic rotational stiffness by imposing a torque-angle relationship control law (Texo = kexo * ∆θankle) where ankle angle was measured with a goniometer. Torque tracking was accomplished by feedback of the applied torque. The ankle exoskeleton work loops for three walking speeds show the change in slope of the work loop representing rotational stiffness (b) Biomechanical measurements performed. (c) Protocol for the three testing sessions