Advanced Compliant Anti-Gravity Robot System for Lumbar Stabilization Exercise Using Series Elastic Actuator

Abstract

Background: The lumbar stabilization exercise is one of the most recommended treatments in medical professionals for patients suffering from low back pain. However, because lumbar stabilization exercise is calisthenics, it is challenging to perform because of the body load of the elderly, disabled, and patients that lack muscle strength. Additionally, it interferes with the effect of exercise because it can strain parts of the body. Methods: To overcome them, a compliant anti-gravity rehabilitation proto-type device using the Series Elastic Actuator (SEA) was developed previously to provide quantitative assist force to the person, producing similar exercise effects with calisthenics. From an exercise experiment with 20 participants, it caused discomfort to participants during exercise owing to the non-ergonomic design of the previous device. Different muscle activation tendencies were observed between calisthenics and exercise using the device. For advanced technical solutions to clinical needs, which is exercise using the rehabilitation robot to produce a similar effect to calisthenics, the mechanical design of the rehabilitation robot was improved based on the previous device after receiving feedback from clinical trials and static analysis. For the safety of exercise using the robot, a cascade PID-PI controller was used to reduce the influence of friction and disturbance due to the external movement. Results: Surface electromyography(sEMG) signal from lumbar muscles showed desired monotonic reduction ratio and higher similarity results compared to the previous device, which proved the exercise effectiveness using the robot. Conclusion: The proposed robot is considered as a solution to a clinical need of lumbar rehabilitation for the elderly, disabled, and patients.