Fig. 8

Mid-level controller of the exoskeleton. The Finite State Machine of the sit-to-stand motion has four main states: sit, stand, standing-up and sitting-down. Four events trigger the change from state to state. In the sit state only the inertial and Coriolis compensation of the exoskeleton is active. In the standing-up state, the gravity compensation is gradually turned on before the seat-off. When the compensation gets one or when the seat-off is detected, the gravity compensation is completely on. When the event to start the assistance is detected, the assistance is switched to active. In the stand state the exoskeleton is completely compensated. In the sitting-down state, gravity compensation is gradually reduced to zero until the person sits back on the stool