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Hybrid Volitional Control for Robotic Ankle Prostheses

Grid of images of activities achieved with Hybrid Volitional Control by all 3 transtibial subject participants.
Activities achieved with Hybrid Volitional Control by all 3 transtibial subject participants.

Overview

For individuals with lower-limb amputation, various activities that require unique ankle movement, such as marching, standing on tip-toes, tapping the foot, and reacting quickly to the environment, are not currently achievable in a reliable way for individuals who have experienced lower-limb amputation. These limitations motivate new control strategies that allow users to easily achieve natural walking gaits, while also giving them more control over the limb to achieve a wider variety of tasks under their own volition.

This research explores a new class of control strategies, known as Hybrid Volitional Control (HVC). HVC consists of a baseline autonomous (non-volitional) control strategy that provides basic gait dynamics to achieve standard activities such as walking on level-ground. Additionally, HVC has a volitional component, which allows the user to directly alter or augment the baseline dynamics in order to achieve voluntary movements. In this work, electromyography (EMG) sensors are explored as a non-invasive approach to enable the volitional alteration that distinguishes HVC. Hybrid Volitional Control has been demonstrated first in simulation, and later in human subject trials where it was compared also to a finite-state machine impedance controller and a direct volitional controller in isolation. This work is being extended to explore the use of other basic controller as the baseline, as well as standardizing the calibration approach for converting user muscle activity into direct ankle movement.

Recent Work

Publications

  • Posh, Ryan R., James P. Schmiedeler, and Patrick M. Wensing. "Hybrid Volitional Control as a Framework for Lower-Limb Prosthetic Control: A Simulation Study." 2021 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS). IEEE, 2021.
  • R. R. Posh, J. P. Schmiedeler, and P. M. Wensing. Finite-state impedance and direct myoelectric control for robotic ankle prostheses: Comparing their performance and exploring their combination. IEEE Transactions on Neural Rehabilitation and Engineering, 31:2778–2788, 2023. doi: 10.1109/TNSRE.2023.3287971.

  • R. R. Posh, J. A. Tittle, J. P. Schmiedeler, and P. M. Wensing. Calibration of a tibia- based phase variable for control of robotic transtibial prostheses. In Proceedings of the IEEE/RSJ International Conference on Intlligent Robots and Systems, pages 2116–2121, Detroit, MI, Oct. 2023. doi: 10.1109/IROS55552.2023.10341724.

  • R. R. Posh, E. C. Barry, J. P. Schmiedeler, and P. M. Wensing. Lower-limb myoelectric calibration postures toward volitional control of transtibial prostheses. IEEE Transactions on Neural Rehabilitation and Engineering, 32:1210–1220, 2024. doi: 10.1109/TNSRE.2024.3375118.

  • R. R. Posh, J. A. Tittle, D. J. Kelly, J. P. Schmiedeler, and P. M. Wensing. Hybrid volitional control of a robotic transtibial prosthesis using a phase variable impedance controller. In IEEE International Conference on Robotics and Automation, 2024. doi: 10.1109/ICRA57147.2024.10610930, (ICRA Best Paper Award Finalist – Medical Robotics).

  • R. R. Posh, J. P. Schmiedeler, and P. M. Wensing. Finite-state impedance and direct myoelectric control for robotic ankle prostheses: Comparing their performance and exploring their combination. IEEE Transactions on Neural Rehabilitation and Engineering, 31:2778–2788, 2023. doi: 10.1109/TNSRE.2023.3287971.

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