Active AFO with ankle joint brake friction control using force observer

Optimum friction control of the ankle joint brake is essential for realizing a stable gait when wearing an active ankle foot orthosis (AFO). An optimum friction control system using a force observer is designed and simulated. The brake friction is controlled in proportion to the observed human force of the lower limb without using force sensors. The simulated results show that the force observer performs well. The force-controlled orthosis is robust and practical because it uses no force sensors.