Stability Control of a Three-Dimensional Passive Walker by Periodic Input Based on the Frequency Entrainment

Abstract

This study proposes a new control that stabilizes a three-dimensional (3D) passive walker without torque input at knees and ankles joints by using entrainment and a mechanical oscillator. It is difficult to stabilize a 3D biped passive walker in different environments because the range of initial conditions for stable walking is limited, so we designed a 3D biped passive walker as a passive walking platform by considering the results of human gait analysis to make the success of passive walking high. The stability of this platform was analytically determined by analyzing the frontal movement limit cycle. In the new control, the frontalmovement period is synchronized with the swing-leg period by a mechanical oscillator on the top of the walker. The mechanical oscillator controller generates a target path to synchronize oscillatormovement with swing-leg movement using frequency entrainment. The walker is stabilized when the frontal movement period was synchronized with the swing-leg period by periodic input generated by the mechanical oscillator. It was experimentally found consequently that the walker was stabilized on different slopes and flat floors.