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First Steps Towards Translating HZD Control of Bipedal Robots to Decentralized Control of Exoskeletons

Agrawal, Ayush and Harib, Omar and Hereid, Ayonga and Finet, Sylvain and Masselin, Matthieu and Praly, Laurent and Ames, Aaron D. and Sreenath, Koushil and Grizzle, Jessy W. (2017) First Steps Towards Translating HZD Control of Bipedal Robots to Decentralized Control of Exoskeletons. IEEE Access, 5 . pp. 9919-9934. ISSN 2169-3536. doi:10.1109/ACCESS.2017.2690407.

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This paper presents preliminary results toward translating gait and control design for bipedal robots to decentralized control of an exoskeleton aimed at restoring mobility to patients with lower limb paralysis, without the need for crutches. A mathematical hybrid dynamical model of the human-exoskeleton system is developed and a library of dynamically feasible periodic walking gaits for different walking speeds is found through nonlinear constrained optimization using the full-order dynamical system. These walking gaits are stabilized using a centralized (i.e., full-state information) hybrid zero dynamics-based controller, which is then decentralized (i.e., control actions use partial state information) so as to be implementable on the exoskeleton subsystem. A control architecture is then developed so as to allow the user to actively control the exoskeleton speed through his/her upper body posture. Numerical simulations are carried out to compare the two controllers. It is found that the proposed decentralized controller not only preserves the periodic walking gaits but also inherits the robustness to perturbations present in the centralized controller. Moreover, the proposed velocity regulation scheme is able to reach a steady state and track desired walking speeds under both, centralized, and decentralized schemes.

Item Type:Article
Related URLs:
URLURL TypeDescription
Harib, Omar0000-0001-9594-0967
Hereid, Ayonga0000-0002-4156-2013
Ames, Aaron D.0000-0003-0848-3177
Grizzle, Jessy W.0000-0001-7586-0142
Additional Information:© 2017 IEEE. IEEE Open Access Publishing Agreement (OAPA). Received March 9, 2017, accepted March 22, 2017, date of publication April 3, 2017, date of current version June 28, 2017. The work of A. Agrawal and K. Sreenath was supported by NSF under Grant IIS-1526515. The work of O. Harib and J. W. Grizzle was supported by NSF under Grant NRI-1525006. The work of A. Hereid was supported by NSF under Grant CPS-1239037. The work of A. D. Ames was supported by NSF under Grant IIS-1526519.
Funding AgencyGrant Number
Subject Keywords:Exoskeletons, control design, robot control
Record Number:CaltechAUTHORS:20170621-161046140
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Official Citation:A. Agrawal et al., "First Steps Towards Translating HZD Control of Bipedal Robots to Decentralized Control of Exoskeletons," in IEEE Access, vol. 5, no. , pp. 9919-9934, 2017. doi: 10.1109/ACCESS.2017.2690407
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:78440
Deposited On:22 Jun 2017 01:30
Last Modified:15 Nov 2021 17:39

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