Abstract
Muscle weakness owing to stroke, spinal cord injuries, or aging can make a person’s life sedentary, temporarily as well as permanently. Such persons need to be motivated to break their sedentary postures and attempt independent motion. A key motivator in this aspect is the ability to easily transition from seated to standing posture. If this sit-to-stand transition (STSt) is easy, it will encourage further mobility. A soft wearable device that can assist the STSt, would fill this need perfectly. Such a device should be able to seamlessly assist during STSt and be unobtrusive during sitting. A major limitation that is currently holding back the development of soft exosuits in STSt-assist is the lack of low-profile soft actuators with high strain rate and force-to-weight ratio. Hence, we propose a novel low-profile vacuum actuator (LPVAc) with an integrated inductive displacement sensor that, can be rapidly fabricated, is lightweight (14g), and can provide high strain (65%) and a high force-to-weight ratio (285 times self-weight). The proposed actuator comprises a low-profile spring encased within a low-density polyethylene film with rapid vacuum actuation and passive quick return. The proposed inductive sensor has a sensitivity of $0.0022~\mu H/mm$ and the hysteresis is below 1.5% with an overall absolute average error percentage of 5.24%. The performance of the proposed integrated sensor in displacement control of the LPVAc is experimentally evaluated. The proposed actuator is integrated into a novel mono-articular STSt-assist exosuit for preliminary testing. Surface electromyography measurements of the gluteus maximus muscles during STSt indicate a mean muscle activity reduction of 45%. This supports the potential use of the proposed actuator in STSt-assist.
Highlights
The quality of life (QoL) of an individual depends on that person’s ability to independently carry out activities of daily living (ADL), such as dressing/bathing, eating, walking and toileting without difficulty [1]
Surface electromyography was used to measure the gluteus maximus (GM) muscle activity during stand transition (STSt). As this exosuit test was carried out in order to evaluate the applicability of the Low-Profile Vacuum Actuator (LPVAc) in driving an STSt-assist exosuit, the LPVAcs were driven in open loop without the use of sensor feedback
A soft exosuit, driven by nonobstructive low-profile actuators, that can be worn while seated can be used in such instances to encourage such patients to frequently and transition from sit-to-stand
Summary
The quality of life (QoL) of an individual depends on that person’s ability to independently carry out activities of daily living (ADL), such as dressing/bathing, eating, walking and toileting without difficulty [1]. Kulasekera et al.: A Low-Profile Vacuum Actuator (LPVAc) with Integrated Inductive Displacement Sensing for a Novel Sit-to-Stand Assist Exosuit tion is advantageous in recovery [3]. They must be encouraged to break their sedentary posture and attempt independent motion.
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