A Hybrid Swing-Assistive Electro-Hydrostatic Bionic Knee Design

The paper presents a novel, semi-active, bionic knee design for transfemoral amputees. The research exploits a linear electro-hydrostatic actuation (EHA) unit, in series with a flow control hydraulic valve, to assist deambulation tasks. High torque, low speed tasks are managed by the hydraulic valve. Conversely, the EHA is exploited in low torque tasks, either in actuation or regeneration mode. Traditional bio-mechanical requirements are discussed and revised to propose a human-centered design. Specifically, the focus is towards amputees comfort and prosthesis fluidity over intact limb motion achievement. The mechatronic design is optimized exploiting a multi-objective evolutionary genetic algorithm and validated by means of computational fluid dynamic (CFD) numerical analyses. Additionally, estimates about mass and size are provided. Finally, a knee prosthesis multi-body model is used to numerically validate the proposed design.