Design and development of soft exosuit for fall intervention

• Main Author: Er, Jie Kai
• Other Authors: Ang Wei Tech
• Format: Theses and Dissertations
• Language: English
• Published: 2019
• Subjects: Engineering::Mechanical engineering::Assistive technology; Engineering::Computer science and engineering::Computing methodologies::Pattern recognition
• Online Access: https://hdl.handle.net/10356/104485; http://hdl.handle.net/10220/50026
• Institution: Nanyang Technological University

The risk of falls along with the severity of its associated injuries increases with age. These injuries have caused significant economic loss for the whole family and their caregivers. Hence, many solutions are being developed to minimise fall risk and reduce fall injuries. Here, a fall intervening novel exosuit that is capable of assisting in recovery actions is proposed. The proposed exosuit will assist in providing a portion of the lumbar extension torque when a trip is detected while remaining transparent during Activities of Daily Living (ADLs). It is hypothesised that the assistive force provided by the exosuit will be sufficient to improve the stability of its user during a trip, as evaluated by balance indicators. The successful realisation of the exosuit depends on many components. These include a fall detection system, a base-suit for force transmission as well as a high bandwidth, high force and high stroke actuator. The developed fall detection system involves three Inertial Measurement Units (IMUs) mounted on the torso and thighs. Each IMU outputs a set of accelerometer and gyroscope data. These data were then passed into a single Hidden Markov Model (HMM) that has been trained using Activities of Daily Living (ADLs). Validation of the system reveals a sensitivity of 90.4%, precision of 87.4%, and an average detection latency of 128.21ms. The base-suit of the exosuit is responsible for providing anchor points and improving the transmission efficiency of the actuator. Two commercially available safety harnesses were used to construct the exosuit. The last component of the exosuit is an actuator that activates only when a fall is detected. This actuator is powered by constant force springs which provided an instantaneous high force output while maintaining its force magnitude throughout the fall recovery period. A novel two-stage design also doubled the stroke while retaining most of the force to perform actual torso extension. Finally, the integrated exosuit was evaluated on 15 healthy subjects for its effectiveness in balance recovery assistance with the extrapolated centre of mass (XCoM). Falls were induced using a fall inducing movable platform (FIMP) which allows transparent overground walking while allowing investigators to randomly induce a repeatable trip with ease. The experimental results proved that the exosuit provided sufficient force at the lumbosacral joint to significantly assist (p<0.001) in the balance recovery of its user.