Self-Contained Powered Knee and Ankle Prosthesis: Initial Evaluation on a Transfemoral Amputee

Abstract

This paper presents an overview of the design and control of a fully self-contained prosthesis, which is intended to improve the mobility of transfemoral amputees. A finite-state based impedance control approach, previously developed by the authors, is used for the control of the prosthesis during walking and standing. The prosthesis was tested on an unilateral amputee subject for over-ground walking. Prosthesis sensor data (joint angles and torques) acquired during level ground walking experiments at a self-selected cadence demonstrates the ability of the device to provide a functional gait similar to normal gait biomechanics. Battery measurements during level ground walking experiments show that the self-contained device provides over 4,500 strides (9.0 km of walking at a speed of 5.1 km/h) between battery charges.

Figures

Fig. 1

The self-contained powered knee and ankle transfemoral prosthesis, front and side views.

Fig. 2

Embedded system framework.

Fig. 3

Complete control architecture showing high, middle and low levels.

Fig. 4

The finite state machine for level walking. Blocks represent states and arrows represent the corresponding transitions.

Fig. 5

The finite state machine for level standing. Blocks represent states and arrows represent the corresponding transitions.

Fig. 6

Unilaterial transfemoral amputee test subject used for the powered prosthesis evaluation.

Fig. 7

Measured joint angles, torques and powers of the powered prosthesis for ten consecutive gait cycles at self-selected speed (5.1 km/h at 87 steps per minute).

Fig. 8

Average electrical power consumption of the powered prosthesis for standing and walking at self-selected speed (5.1 km/h at 87 steps per minute) on normal ground.