Abstract
The evolution to bipedalism forced humans to develop suitable strategies for dynamically controlling their balance, ensuring stability, and preventing falling. The natural aging process and traumatic events such as lower-limb loss can alter the human ability to control stability significantly increasing the risk of fall and reducing the overall autonomy. Accordingly, there is an urgent need, from both end-users and society, for novel solutions that can counteract the lack of balance, thus preventing falls among older and fragile citizens. In this study, we show a novel ecological approach relying on a wearable robotic device (the Active Pelvis Orthosis, APO) aimed at facilitating balance recovery after unexpected slippages. Specifically, if the APO detects signs of balance loss, then it supplies counteracting torques at the hips to assist balance recovery. Experimental tests conducted on eight elderly persons and two transfemoral amputees revealed that stability against falls improved due to the “assisting when needed” behavior of the APO. Interestingly, our approach required a very limited personalization for each subject, and this makes it promising for real-life applications. Our findings demonstrate the potential of closed-loop controlled wearable robots to assist elderly and disabled subjects and to improve their quality of life.
Highlights
In this study, we show that this approach can be implemented improving balance recovery in elderly people and transfemoral amputees
The A-mode consisted in applying synchronous extensor and flexor torques (Fig. 1C) based on the subjects’ body weight, to the perturbed (PL) and the unperturbed (UL) limbs, respectively, in order to counteract the downward displacement of the center of mass (COM; Materials and Methods, Section B; as representative examples, see Movie S1 and Movie S2)
The reactive behavior of elderly participants was not altered by the use of the exoskeleton in Z-mode in terms of both kinematics and stability, revealing that the APO was unobtrusive with respect to the experimental conditions. All these findings indicate that the light-weighted APO can detect in real-time the onset of a mechanical perturbation and activate specific mitigation strategies to promote balance recovery
Summary
We show that this approach can be implemented improving balance recovery in elderly people and transfemoral amputees. These two groups of subjects represent persons whose risks of fall ranges from moderate to severe[3,4,14,15], they can be considered as potential users who can take advantages from a wearable assistive device To achieve this goal a novel control algorithm[16], leading an Active Pelvis Orthosis[17]. (APO; Fig. 1 and Fig. S1, Supplementary Materials and Methods, Section B), was designed to: i) be transparent to the user’s intended movements during unperturbed motor tasks, ii) identify in real time the onset of an unexpected slipping-like perturbation[16] (Fig. 2A) and iii) generate countermeasures to restore user’s stability against falling
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