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Assist-As-Needed Control of a Hip Exoskeleton, Using Central Pattern Generators in a Stride Management Strategy

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Abstract

This paper proposes a novel stride management strategy for rehabilitation exoskeletons. This method incorporates a Central Pattern Generator (CPG) into an Assist-As-Needed (AAN) controller to induce an optimal stride length for the wearers and optimize the energy consumption. Most AAN controllers rely on a predefined and fixed trajectory to measure the required amount of assistance. However, for a stride management approach, the trajectory should be updated regularly according to the wearer’s performance to induce the optimal stride length eventually. The proposed stride management strategy deals with this challenge by integrating a CPG into the control loop. The CPG updates the desired trajectory right after each swing phase. The AAN controller uses a recently introduced Strength Index (SI) for continuous measurement of the wearer’s ability in tracking the desired trajectory. A virtual tunnel around the desired trajectory is defined, and the tunnel boundaries are adjusted according to the SI. Then, an adaptive impedance controller determines the assistive force according to the distance between the actual trajectory of the user and the tunnel boundaries. The performance of the proposed method is evaluated in OpenSim software, and reductions in the metabolic cost and muscles’ activity are observed.

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Acknowledgements

We would like to first thank all members of the Ferdowsi University of Mashhad Robotics Lab for their kind participation and cooperation.

Funding

This research is supported by grant #101120 from the Ferdowsi University of Mashhad-Iran and grant #962297 from the National Institute for Medical Research Development of Iran. This research is also supported by the National Elites Foundation of Iran.

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Authors and Affiliations

  1. Mechanical Engineering Department, Ferdowsi University of Mashhad, Mashhad, Iran

    Naeim Naghavi, Alireza Akbarzadeh, Omid Khaniki & Iman Kardan

  2. Center of Excellence On Soft Computing and Intelligent Information Processing (SCIIP), Ferdowsi University of Mashhad, Mashhad, Iran

    Naeim Naghavi, Alireza Akbarzadeh & Omid Khaniki

  3. Center of Advanced Rehabilitation and Robotics Research (FUM-CARE), Ferdowsi University of Mashhad, Mashhad, Iran

    Naeim Naghavi, Alireza Akbarzadeh, Omid Khaniki, Iman Kardan & Ali Moradi

  4. Orthopedic Research Center, Ghaem Hospital, Mashhad University of Medical Sciences, Mashhad, Iran

    Ali Moradi

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Naghavi, N., Akbarzadeh, A., Khaniki, O. et al. Assist-As-Needed Control of a Hip Exoskeleton, Using Central Pattern Generators in a Stride Management Strategy. J Intell Robot Syst 107, 53 (2023). https://doi.org/10.1007/s10846-023-01854-x

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