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

Abstract

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. 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. The mechanical structure and control strategy of the prosthesis were demonstrated. The performance of the prosthesis was tested by bench and human tests. Passive subsystem damping adjustment ranges from 0.4 N⋅(mm/s)-1 to 300 N⋅(mm/s)-1. The switching time between the damping and the active subsystem is 32 ± 2 ms. The continuous active torque output is more than 24 Nm. In level walking, the peak torque is about 28 Nm. The proposed active-passive hybrid hydraulic prosthesis could satisfy both low passive friction and high active actuation.