Mathematical Model and Design Exploration of Soft Comfortable, Effective Anchoring for Wearable Assistive Technologies

Exoskeletons provide excellent assistance and rehabilitation to people with mobility difficulties including ageing people, stroke survivors and people suffering from frailty and sarcopenia. However, comfortable wearing and easy donning and doffing of exoskeletons remain the major challenges. Standard exoskeleton anchoring methods, such as tight braces and Velcro straps, have drawbacks including long attachment time and discomfort, causing skin irritation and muscle soreness. A soft fabric shrink-to-fit pneumatic sleeve was previously developed, introducing comfortable and active anchoring for upper limb assistance. This study further develops the mathematical model deriving the shrink-to-fit size range and the maximum pulling resistance based on selected design parameters of an anchoring module and its applied pressure. The study also investigates various limb shapes of human body and explores four different designs of soft anchoring units by assessing their anchoring performance, where high pulling resistance at low body compression is preferred. It was found that rectangular units work well for smooth cylindrical-shaped limbs, conical units perform well with conical-shaped limbs, multiple-row pouch designs are best for concave limbs, and Kirigami designs are ideal for expanding limbs due to their inherent stretchability. Additionally, a prototype combining multiple anchoring designs for an upper limb was developed.