The THKAF walking assistance device described in [37] aims at
aiding elderly and impaired people. Its actuation system is placed
in a backpack, with transmission employing flexible shafts: the
torques effectively applied to the active joints – knee and ankle
– are calculated on the basis of the shaft twist angle. The desired
joints angles and torques are referred to gaits data of healthy
people. Rather than tracking only one kind of desired signal, only
angles or only torques, the actuators’ final outputs are determined
by hybridizing the joints angles controller and torques controller
with a certain ratio (experimentally chosen).