Finite Time Robust Control of the Sit-to-Stand Movement for Powered Lower Limb Orthoses

TL;DR

This paper develops a robust control method for powered lower limb orthoses to safely perform Sit-to-Stand movements despite parameter uncertainties, using a finite time horizon LQR approach optimized for robustness.

Contribution

It introduces a novel finite time robust control technique that optimizes LQR gains considering parameter uncertainties for Sit-to-Stand movements.

Findings

The method improves safety and robustness in simulated Sit-to-Stand movements.

Comparison shows enhanced performance over previous control strategies.

Robust performance metrics effectively quantify deviation under uncertainties.

Abstract

This study presents a technique to safely control the Sit-to-Stand movement of powered lower limb orthoses in the presence of parameter uncertainty. The weight matrices used to calculate the finite time horizon linear-quadratic regulator (LQR) gain in the feedback loop are chosen from a pool of candidates as to minimize a robust performance metric involving induced gains that measure the deviation of variables of interest in a linear time-varying (LTV) system, at specific times within a finite horizon, caused by a perturbation signal modeling the variation of the parameters. Two relevant Sit-to-Stand movements are simulated for drawing comparisons with the results documented in a previous work.