An adaptive neuromuscular controller for assistive lower-limb exoskeletons

An adaptive neuromuscular controller for assistive lower-limb exoskeletons: A preliminary study on subjects with spinal cord injury

Wu, Amy R. (Swiss Federal Institute of Technology)
Dzeladini, Florin (Swiss Federal Institute of Technology)
Brug, Tycho J.H. (University of Twente)
Tamburella, Federica (Fondazione Santa Lucia (IRCCS))
Tagliamonte, Nevio L. (Fondazione Santa Lucia (IRCCS))
Van Asseldonk, Edwin H.F. (University of Twente)
van der Kooij, H. (TU Delft Biomechatronics & Human-Machine Control; University of Twente)
Ijspeert, Auke J. (Swiss Federal Institute of Technology)

2017

Versatility is important for a wearable exoskeleton controller to be responsive to both the user and the environment. These characteristics are especially important for subjects with spinal cord injury (SCI), where active recruitment of their own neuromuscular system could promote motor recovery. Here we demonstrate the capability of a novel, biologically-inspired neuromuscular controller (NMC) which uses dynamical models of lower limbmuscles to assist the gait of SCI subjects. Advantages of this controller include robustness, modularity, and adaptability. The controller requires very few inputs (i.e., joint angles, stance, and swing detection), can be decomposed into relevant control modules (e.g., only knee or hip control), and can generate walking at different speeds and terrains in simulation. We performed a preliminary evaluation of this controller on a lower-limb knee and hip robotic gait trainer with seven subjects (N = 7, four with complete paraplegia, two incomplete, one healthy) to determine if the NMC could enable normal-like walking. During the experiment, SCI subjects walked with body weight support on a treadmill and could use the handrails. With controller assistance, subjects were able to walk at fast walking speeds for ambulatory SCI subjects-from 0.6 to 1.4 m/s. Measured joint angles and NMC-provided joint torques agreed reasonably well with kinematics and biological joint torques of a healthy subject in shod walking. Some differences were found between the torques, such as the lack of knee flexion near mid-stance, but joint angle trajectories did not seem greatly affected. The NMC also adjusted its torque output to provide more joint work at faster speeds and thus greater joint angles and step length. We also found that the optimal speed-step length curve observed in healthy humans emerged formost of the subjects, albeit with relatively longer step length at faster speeds. Therefore, with very few sensors and no predefined settings for multiple walking speeds or adjustments for subjects of differing anthropometry and walking ability, NMC enabled SCI subjects to walk at several speeds, including near healthy speeds, in a healthy-like manner. These preliminary results are promising for future implementation of neuromuscular controllers on wearable prototypes for real-world walking conditions.

Biomechanics
Exoskeleton
Locomotion
Neuromuscular controller
Spinal cord injury

http://resolver.tudelft.nl/uuid:5b96740c-35f5-4845-bfe4-1792717ecd51

https://doi.org/10.3389/fnbot.2017.00030

Frontiers in Neurorobotics, 11

Institutional Repository

journal article

© 2017 Amy R. Wu, Florin Dzeladini, Tycho J.H. Brug, Federica Tamburella, Nevio L. Tagliamonte, Edwin H.F. Van Asseldonk, H. van der Kooij, Auke J. Ijspeert