Monte Carlo Simulation of Gas Spring in an Energy Storing Prosthetic Knee

Abstract

Gas Spring is an important component of an energy storing prosthetic knee. The spring stored energy during flexion and released the energy while in the extension. In this research, we discuss a Monte Carlo simulation model of a gas spring in an Energy Storing Prosthetic Knee (ESPK) using Oracle Crystal Ball software. The simulation is used to predict the effects of three important design variables of a gas spring which are cylinder diameter, cylinder length, and displacement to the energy storing performance of the spring. The results of simulation show that there are two design variables which have significant contribution to the variations of energy storing performance: cylinder diameter and displacement. Those design variables account for 99.3% to the total variance of energy storing. Quality improvement must be conducted to lowering the resulted energy storing variance. We proportionally decrease the variance of the design variables to lowering the energy storing variance. The simulation results show a significant quality improvement of about 50% in term of energy storing standard deviation. The results also show that cylinder diameter is more sensitive than the other two design variables in energy storing quality improvement.