Frequency Domain Analysis of Nonlinear Series Elastic Actuator via Describing Function

TL;DR

This paper introduces a frequency domain analysis method for nonlinear series elastic actuators using the describing function, enabling better design and control of assistive robots with nonlinear stiffness.

Contribution

It applies the describing function approach to analyze nonlinear SEAs in the frequency domain, filling a gap in systematic design methods for these actuators.

Findings

Provides a new analytical framework for nonlinear SEA analysis

Enables frequency domain understanding of nonlinear stiffness effects

Supports improved design and control strategies for assistive robots

Abstract

Nonlinear stiffness SEAs (NSEAs) inspired by biological muscles offer promise in achieving adaptable stiffness for assistive robots. While assistive robots are often designed and compared based on torque capability and control bandwidth, NSEAs have not been systematically designed in the frequency domain due to their nonlinearity. The describing function, an analytical concept for nonlinear systems, offers a means to understand their behavior in the frequency domain. This paper introduces a frequency domain analysis of nonlinear series elastic actuators using the describing function method. This framework aims to equip researchers and engineers with tools for improved design and control in assistive robotics.