Estimation of Minimum Stride Frequency for the Frontal Plane Stability of Bipedal Systems

TL;DR

This paper investigates how key parameters influence the minimum stride frequency needed for stable frontal plane bipedal locomotion, proposing a predictive method to enhance understanding and control efficiency.

Contribution

It introduces a method to predict minimum stride frequency based on model parameters, advancing knowledge of stability mechanisms in bipedal systems.

Findings

Predicted stride frequencies closely match actual values in tests.

System parameters significantly influence stability and minimum stride frequency.

Feedforward stabilization reduces control effort and energy expenditure.

Abstract

Stability of bipedal systems in frontal plane is affected by the hip offset, to the extent that adjusting stride time using feedforward retraction and extension of the legs can lead to stable oscillations without feedback control. This feedforward stabilization can be leveraged to reduce the control effort and energy expenditure and increase the locomotion robustness. However, there is limited understanding of how key parameters, such as mass, stiffness, leg length, and hip width, affect stability and the minimum stride frequency needed to maintain it. This study aims to address these gaps through analyzing how individual model parameters and the system's natural frequency influence the minimum stride frequency required to maintain a stable cycle. We propose a method to predict the minimum stride frequency, and compare the predicted stride frequencies with actual values for randomly generated models. The findings of this work provide a better understanding of the frontal plane stability mechanisms and how feedforward stabilization can be leveraged to reduce the control effort.