Abduction/Adduction Assistance from Powered Hip Exoskeleton Enables Modulation of User Step Width During Walking

Abstract

<p>Abstract-Using wearable robotics to modulate step width in normal walking for enhanced mediolateral balance has not been demonstrated in the field. We designed a bilateral hip exoskeleton with admittance control to power hip abduction and adduction to modulate step width. Objective: As the first step to show its potential, the objective of this study was to investigate how human’s step width reacted to hip exoskeleton’s admittance control parameter changes during walking. </p> <p>Methods: Ten non-disabled individuals walked on a treadmill at a self-selected speed, while wearing our bilateral robotic hip exoskeleton. We used two equilibrium positions to define the direction of assistance. We studied the influence of multiple stiffness values in the admittance control on the participants’ step width, step length, and electromyographic (EMG) activity of the gluteus medius. Results: Step width were significantly modulated by the change of stiffness in exoskeleton control, while step length did not show significant changes. When the stiffness changed from zero to our studied stiffness values, the participants’ step width started to modulate immediately. Within 4 consecutive heel strikes right after a stiffness change, the step width showed a significant change. Interestingly, EMG activity of the gluteus medius did not change significantly regardless the applied stiffness and powered direction. </p> <p>Conclusion: Tuning of stiffness in admittance control of a hip exoskeleton, acting in mediolateral direction, can be a viable way for controlling step width in normal walking. Unvaried gluteus medius activity indicates that the increase in step width were mainly caused by the assistive torque applied by the exoskeleton. </p> <p>Significance: Our study results pave a new way for future design and control of wearable robotics in enhancing mediolateral walking balance for various rehabilitation applications. </p>

Single-Actuator Hip Exoskeleton Mechanism Design With Actuation in Frontal and Sagittal Planes: Design Methodology and Experimental Validation

“…The input moments of the mechanism are generated by using a closed-loop admittance control strategy [8], [23]. This strategy takes into account the compliance of the flexible shaft used to transmit power from the motor to the test bench.…”

“…Biomechanical simulations have suggested that muscles involved in hip abduction (outward rotation on the frontal plane) are the most effective for reducing metabolism [6]. It has been proposed that an exoskeleton that assists the frontal plane can control the step width, improving walking stability [7], [8]. Thus, within the context of the three-dimensional moments governing walking, both the sagittal plane moment contributing to forward propulsion and the frontal plane moment contributing to stability are essential.…”

Stride Width Estimation in Individuals with and without Neurodegenerative Disease via a Novel Data-Augmentation Deep Learning Model and Minimal Wearable Inertial Sensors

“…While previous research has predominantly focused on anterior-posterior gait parameters such as stride length and walking speed, limited attention has been given to mediolateral measurement, particularly stride width [3], [4]. However, stride width, associated with foot placement strategy and influencing the interaction between the body's center of mass and base of support [5]- [7], plays a crucial role in gait stability, postural balance control, and fall risk reduction for both healthy subjects and individuals with neurodegenerative disease [8]- [11]. Through active adjustment of stride width, individuals optimize energy efficiency [6], enhance dynamic margins of stability [12], negotiate small obstacles [13], and overcome external disturbances during walking [14].…”

“…Stride width is also linked to gait compensatory mechanisms and serves as a modifiable factor in effective fall prevention training [8], [19]. Individuals with neurodegenerative disease, especially those with cerebellar ataxia, often exhibit a wider stride width to mitigate fall risks, counteract trunk instability, and enhance adaptability [19]- [22].…”