Development of A Non-Power Waist Assist Device and IEMG-Based Evaluation of Assist Effect

Long-term work in a stooped posture and lifting heavy loads may cause the lumbar muscle strain and various lumbar diseases. Nowadays, most waist assist devices are power-assisted, which are limited to inconveniences like complicated structure, large volume and confining power source. To solve the problems above, this paper proposes a wearable lightweight unpowered waist assist device (LWA). The LWA can store the gravitational potential energy in the torsion spring as the wearer bends, and release the energy to help the wearer lift the heavy object later on. 15 test subjects participating in research experiments, carry 5-25kg boxes without and with the LWA respectively. The assist ratio is evaluated by measuring the surface electromyography (EMG) signals of the lumbar erector spine (LES), the thoracic erector spine (TES), the latissimus dorsi (LD) and the rectus abdominis (RA) of the test subjects, who wear and don't wear the LWA. According to the tests, when carrying a 25kg heavy object, the LES assisting effect is 20.03%, the TES assisting effect is 21.35%, and the LD assisting effect is 15.01%. The experimental results show that the LWA can reduce the burden and discomfort of the back muscles during long-term bending work.