An Intelligent Control Approach for Reduction of Gait Asymmetry in Transfemoral Amputees

Traumatic injuries, vascular deficiencies, or complications from diabetes can lead to amputation of the lower extremities of an individual. Depending on the severity, amputation can be performed by removing a portion of the limb below the knee (Transtibial Amputation), or the entire limb below the hip (above knee or Transfemoral Amputation). After amputation, individuals seldom regain complete mobility even with the assistance of prosthetic limb. Further, the individual usually suffers from complications such as pain in the residual limb, infections, muscular atrophy, fatigue, and emotional trauma. One of the factors that has significant impact on the long-term health of the amputee is the asymmetry in the gait of the intact and prosthetic limbs. In this paper, we present a case study to demonstrate how gait asymmetry can lead to reduced stance time on the prosthetic limb. Reduced stance time implies that the individual depends more on the intact limb for support and mobility. Over the long term, such asymmetry can lead to musculo-skeletal and cardiac problems and result in additional surgeries. While active prosthesis can improve mobility of the individual, the devices in use today have limitations that prevent gait symmetry. The main challenge in designing a controller for an active prosthesis is that the intent of the user is unknown. Therefore, it is not possible to design trajectories for the prosthetic joints to follow. In the second half of the paper, an intelligent control approach is developed that adapts to the gait of the individual and reduces the asymmetry between the healthy and prosthetic limb.