Prediction of three-dimensional crutch walking patterns using a torque-driven model
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Prediction of three-dimensional crutch walking patterns using a torque-driven model Míriam Febrer-Nafría1 · Roger Pallarès-López1 · Benjamin J. Fregly2 · Josep M. Font-Llagunes1
Received: 2 November 2019 / Accepted: 16 June 2020 © Springer Nature B.V. 2020
Abstract Computational prediction of 3D crutch-assisted walking patterns is a challenging problem that could be applied to study different biomechanical aspects of crutch walking in virtual subjects, to assist physiotherapists to choose the optimal crutch walking pattern for a specific subject, and to help in the design and control of exoskeletons, when crutches are needed for balance. The aim of this work is to generate a method to predict threedimensional crutch-assisted walking motions following different patterns without tracking any experimental data. To reach this goal, we collected gait data from a healthy subject performing a four-point non-alternating crutch walking pattern, and developed a 3D torquedriven full-body model of the subject including the crutches and foot- and crutch-ground contact models. First, we developed a predictive (i.e., no tracking of experimental data) optimal control problem formulation to predict crutch walking cycles following the same pattern as the experimental data collected, using different cost functions. To reduce errors with respect to reference data, a cost function combining minimization terms of angular momentum, mechanical power, joint jerk and torque change was chosen. Then, the problem formulation was adapted to handle different foot- and crutch-ground conditions to make it capable of predicting three new crutch walking patterns, one of them at different speeds. A key aspect of our algorithm is that having ground reactions as additional controls allows one to define phases inside the cycle without the need of formulating a multiple-phase problem, thus facilitating the definition of different crutch walking patterns.
B M. Febrer-Nafría
[email protected] R. Pallarès-López [email protected] B.J. Fregly [email protected] J.M. Font-Llagunes [email protected]
1
Department of Mechanical Engineering & Research Centre for Biomedical Engineering, Universitat Politècnica de Catalunya, Barcelona, Spain
2
Dept. of Mechanical Engineering, Rice University, Houston, TX, USA
M. Febrer-Nafría et al.
Keywords Crutch walking · Optimal control · Human motion prediction · Direct collocation
1 Introduction Spinal cord injury (SCI), which is commonly caused by falls in the elderly and traffic accidents [1], affects between 250,000 and 500,000 people worldwide each year [2]. Walking impairment after SCI leads to a decreased quality of life and other serious health conditions (e.g., heart disease, high blood pressure) and carries substantial health care costs. Gait restoration of these patients can be partially achieved by powered orthoses and exoskeletons, which usually require the aid of crutches or walkers for balance. This requirement could induce undesirable outcomes if the achieved walking pattern has un
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