Design and evaluation of a novel soft active-vest for human back assistance

Back muscle weakness and lower back pain affect the quality of life and productivity at work, and such age-related problems are prevalent among middle-aged and elderly people. Wearable exoskeletons/soft suits offer substantial promise as a means to augment strength, assist movement and improve stability of the human body. This thesis presents the design, modelling and evaluation of a novel soft suit (“Active-Vest”) for human back support. Active-Vest is human-friendly, flexible, lightweight and able to reduce the efforts of back muscles and reaction forces at the lumbar spine joints during flexion-flexion motions of the back in the sagittal plane. The design of the Active-Vest allows the support of the back without involving the lower limbs, meaning it may provide a better walking experience. The assistance capabilities and safe application of the vest design were assessed in OpenSim software employing a series of biomechanical models of the proposed vest united with an enhanced human musculoskeletal model assembly. The simulation revealed that the soft actuator system reduced the erector spinae muscle force required to articulate the back during flexion-extension motions in the sagittal plane by 60%. Simultaneously, the maximum compression and shearing forces acting on the lumbosacral and L1-L2 joints were reduced by 39% and 32% respectively, as the vest actuators act on a larger lever arm than the corresponding muscles. The Active-Vest prototype has been fabricated and laboratory evaluations on a healthy subject have been performed to quantify human-vest interaction. Evaluations confirmed that wearing the vest reduced the magnitude of the surface Electromyography signal (EMG) of erector spinae muscles by 61% during said flexion-extension motions in the sagittal plane, supporting the prediction of the computer simulations of reduced erector spinae muscle activity and reduced reaction force at lumbar joints. Further, the prototype reduced the EMG signal by 43% to maintain the trunk status in the transverse plane against gravity. These results demonstrate the practicability and promise of Active-Vest to aid people with reduced back strength and to decrease lower back pain and risk of back injury. Considering these promising results, the methods proposed in this work contribute towards a more human-back assistance/lower back pain/injury risk reduction. In future, the vest will be able to involve the aid of all spinal range of motions and present the feasibility of wide-community utilization. Future work will increase the number of actuators of the Active-Vest and the vest could be expanded to a full body suit