Towards Accurate Force Control of Series Elastic Actuators Exploiting a Robust Transmission Force Observer

TL;DR

This paper introduces a novel transmission force observer (TFOB) for series elastic actuators, significantly enhancing force measurement accuracy by addressing nonlinearities and noise, and is validated through experiments.

Contribution

The paper presents a new force estimation scheme (TFOB) that improves force control accuracy in SEAs by analyzing stochastic characteristics and providing an optimal tuning method.

Findings

TFOB outperforms conventional force sensing methods.

Experimental results confirm improved force control accuracy.

Optimal tuning parameter derived from frequency domain analysis.

Abstract

This paper develops an accurate force control algorithm for series elastic actuators (SEAs) based on a novel force estimation scheme, called transmission force observer (TFOB). The proposed method is designed to improve an inferior force measurement of the SEA caused by nonlinearities of the elastic transmission and measurement noise and error of its deformation sensor. This paper first analyzes the limitation of the conventional methods for the SEA transmission force sensing and then investigates its stochastic characteristics, which indeed provide the base to render the accurate force control performance incorporated with the TFOB. In particular, a tuning parameter is introduced from holistic closed-loop system analyses in the frequency domain. This gives a guideline to attain optimum performance of the force-controlled SEA system. The proposed algorithm is experimentally verified in an actual SEA hardware setup.