Bifurcation and Chaotic Behaviors of a Passive Bipedal Walker with Leg Length Discrepancy and Unequal Leg Mass

다국어 초록 (Multilingual Abstract)

Asymmetric gait patterns may be observed in people with neurological or musculoskeletal disorders, in addition to healthy individuals. With reference to widely accepted research, leg length discrepancy and unequal leg mass are the main and direct causes of gait asymmetry, respectively. In previous studies, the independent influences of leg length discrepancy and unequal leg mass on gait patterns were investigated. However, the simultaneous effects of these factors on the gait patterns are unclear. It is therefore necessary to examine the effect of both factors on gait dynamics to determine the factors that cause more severe gait asymmetry. In this study, the effects of leg length discrepancy and unequal leg mass on gait patterns were investigated using a passive dynamic walking model. The findings revealed that gait asymmetry was more sensitive to leg length discrepancy than unequal leg mass by a factor of 60. As the rate of leg length and mass discrepancy changed, the output parameters characterizing the entire gait apparatus, such as step period, joint angular displacement, and joint angular speed, exhibited chaotic behaviors with bifurcations. Furthermore, when leg length discrepancy and unequal leg mass were simultaneously applied to the walking model, the effects of each factor on gait independently affect the gait patterns and gait patterns did not change in a new and unpredictable manner owing to nonlinearity. We expected that the asymmetric gait dynamics investigated in this study will contribute to the development of lower limb prosthetics and the gait training of patients with gait asymmetry.