A control method of ankle foot orthosis (AFO) with artificial muscle

We developed a new ankle foot orthosis (AFO) using artificial muscle. In AFO two pressure sensors are arranged in the bottom of the foot. One is located on the toe and other is located on the heel. The control consists of four control sequences such that (1) when the heel touches down on the floor, the pressure of artificial muscle goes to zero gradually, (2) when the toe touches down on the floor after the touch down of the heel, the pressure of artificial muscle is still off, (3) when the heel leaves from the floor, the pressure of artificial muscle is zero, (4) when the toe leaves from the floor, the pressure of artificial muscle becomes a certain value, hence, the artificial muscle is shortened. From the experimental data of a disabled patient it is revealed that this control law yields the faster walking and the shorter swing length. Also, especially, it is clarified that in the action shown by (2) above the plantar flexion control is very important for early recovery of walking ability. In this paper we focus our attention to the development of a new control law to improve the rehabilitation performance based on the plantar flexion control.