Design,fabrication and experiments of a hydraulic active-passive hybrid prosthesis knee

Abstract

BACKGROUND:

Due to low friction, passive mechanical prostheses move compliantly followed by the stump and are used widely. Advanced semi-active prostheses can both move passively like passive prostheses and provide active torque under specific conditions. However, the current mechanical-hydraulic coupling driven semi-active prostheses, in order to meet the low passive friction requirements with a low active transmission ratio, lead to a significant problem of insufficient active torque.

OBJECTIVE:

A hybrid active and passive prosthesis was developed to solve the incompatibility problem of low passive friction and high active driving torque of semi-active prostheses.

METHODS:

The mechanical structure and control strategy of the prosthesis were demonstrated. The performance of the prosthesis was tested by bench and human tests.

RESULTS:

Passive subsystem damping adjustment ranges from 0.4 N $\cdot$ (mm/s) ${}^{-1}$ to 300 N $\cdot$ (mm/s) ${}^{-1}$ . The switching time between the damping and the active subsystem is 32 $\pm$ 2 ms. The continuous active torque output is more than 24 Nm. In level walking, the peak torque is about 28 Nm.

CONCLUSION:

The proposed active-passive hybrid hydraulic prosthesis could satisfy both low passive friction and high active actuation.