Biologically based design of an actuator system for a knee–ankle–foot orthosis

Knee–ankle–foot orthosis are systems used to restore human gait, providing stability during stance phase. A concept of actuator for knee–ankle–foot orthosis was developed based on biomechanical data. The actuator is conceived to provide mechanical means to reproduce the normal kinematics during human gait at joint level. Behaviour of the joints of the lower limb was approximated by elastic means and an actuator for each joint was designed and constructed. The rationale of the design process is presented, considering the functional aspects and aiming at a lightweight solution with low power demand. Tests performed with one patient suffering from post-poliomyelitis syndrome are presented and evidence of functional compensation during stance and swing phases with the proposed solution is given.