The lower extremity
exoskeleton comprises two leg supports connectable to person's lower limbs and configured to rest on the ground during their
stance phase. Each leg support comprises a
thigh link and a shank link; a
knee joint configured to allow flexion and extension between the shank link and the
thigh link. The lower extremity
exoskeleton further comprises an
exoskeleton trunk connectable to the person'supper body. The exoskeleton
trunk is connectable to the
thigh links of the leg supports allowing for the flexion and extension between the leg supports and the exoskeleton
trunk. Two torque generators are coupled to each of the knee joints. A
power unit, capable of providing power, is coupled to the torque generators. In operation when a leg support is in a
stance phase and climbing a slope or
stairs, the
power unit injects power into the respective torque generator thereby extending the respective knee angle. When a leg support is in
stance phase and not climbing a slope or
stairs, the
power unit does not inject any power to the respective torque generator, but without dissipating any stored power in said power unit, it forces the torque generator to
resist flexion of the respective
knee joint. When a leg support is in a swing phase, the power unit does not inject any power to the respective torque generator, but without dissipating any stored power in said power unit, it forces the torque generator to minimize its resistance to
knee flexion and extension.