Passive Dynamic Walking Analysis

There are an estimated 1.7 million Americans living with limb loss; further, spinal cord injuries afflict 250,000 Americans [1]. Many patients lose their jobs and their quality of life plummets. Fortunately there have been significant advancements in the design of prosthetic limbs in the last few decades. A noteworthy achievement is the direct integration of a prosthetic device with the brain, termed a neuroprosthesis device. An electrode is implanted in the brain of the patient which records the electrical activity of the neurons associated with motor movement and controls the prosthetic device. These have been successfully implemented for simple upper limb movements [2]. However, efficient and cost-effective lower limb prosthetic devices have not yet appeared on the market. Investigating passive dynamic walking determines the extent to which the natural human gait depends on passive dynamics. More efficient prosthetic models can be developed from these principles. A thorough mathematical investigation of passive dynamic walking is necessary to replicate the stability of the human locomotor system. This requires an understanding of the physical basis of walking and an understanding of the biological processes underlying motor movement. The first model investigated was a passive walking model based on a double pendulum which exhibits a single stable periodic solution. The robustness of this solution was investigated as the angle of incline and the weights of the feet were varied. Continuation of the solution was also performed as the incline angle and mass distribution were continuously varied. The second model investigated was a passive walking model with rockers on its feet, which rolled without slipping on the surface. McGeer terms it the ”walking wheel” [5]. This model’s regions of stability were much larger than those of the simple pendulum model.