Title:
First Steps Toward Translating Robotic Walking To Prostheses: A Nonlinear Optimization Based Control Approach
First Steps Toward Translating Robotic Walking To Prostheses: A Nonlinear Optimization Based Control Approach
Author(s)
Zhao, Huihua
Horn, Jonathan
Reher, Jacob
Paredes, Victor
Ames, Aaron D.
Horn, Jonathan
Reher, Jacob
Paredes, Victor
Ames, Aaron D.
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Abstract
This paper presents the first steps toward successfully
translating nonlinear real-time optimization based controllers
from bipedal walking robots to a self-contained powered
transfemoral prosthesis: AMPRO, with the goal of improving
both the tracking performance and the energy efficiency
of prostheses control. To achieve this goal, a novel
optimal control strategy combining control Lyapunov function
(CLF) based quadratic programs (QP) with impedance
control is proposed. This optimal controller is first verified
on a human-like bipedal robot platform, AMBER. The results
indicate improved (compared to variable impedance
control) tracking performance, stability and robustness to
unknown disturbances. To translate this complete methodology
to a prosthetic device with an amputee, we begin by collecting
reference human locomotion data via Inertial measurement
Units (IMUs). This data forms the basis for an
optimization problem that generates virtual constraints, i.e.,
parameterized trajectories, specifically for the amputee and
the prosthesis. A online optimization based controller is utilized to optimally track the resulting desired trajectories. The parameterization of the trajectories is determined through
a combination of on-board sensing on the prosthesis together
with IMU data, thereby coupling the actions of the user with
the controller. Importantly, the proposed control law displays
remarkable tracking and improved energy efficiency,
outperforming PD and impedance control strategies. This
is demonstrated experimentally on the prosthesis AMPRO
through the implementation of the holistic sensing, algorithm
and control framework, with the end result being stable
prosthetic walking by an amputee.
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Date Issued
2016
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