Knee preservation in below knee (BK) amputees leads to less deviation from normal gait compared to above knee amputees; however, the below knee amputees must contend with substantial challenges due to functional loss of ankle joint. Hence, in order to improve the quality of motion among these subjects, the embedded spring module, in available commercial passive prosthesis, restores and returns energy during walking to compensate for the lost limb. While most of the researches in this field, concentrate on the influence of ankle stiffness on metabolic rate and energy expenditure during walking, the effect of stiffness on highest achievable speed is not well understood. The objective of this paper is to understand this effect. To this end, a mathematical framework is used to simulate fast walking of a below knee amputee. The problem is solved for the highest achievable speed of the model with phase plane method and the effect of different ankle stiffness is investigated. In addition the effect of damping ratio on walking speed is also studied. These results can be used in design of BK prosthesis for amputees with higher levels of activities.

Full text: IJEIR_1643_Final.pdf