A wearable exoskeletal lumbar spinal rehabilitation robot based on sliding mode control scheme

Abstract

Low back pain has become the leading cause of nonfatal health damage in the world, and about 80% of people are affected at some stage of their lives. Lumbar disc herniation (LDH) is the most common clinical cause of low back pain, of which nonsurgical treatment of lumbar traction combined with long-term bed rest can cure 80% to 90% of patients clinically. However, long-term bed rest is difficult to achieve for many people, and the use of traction equipment is expensive and inconvenient. In this paper, we developed a wearable exoskeletal lumbar rehabilitation robot (WELRR) to replace the traditional treatment of mechanical traction and long-term bed rest. The WELRR allows people to continuously wear at work and life with lumbar vertebra supported. In addition, for patients that require 2-3 months of rehabilitation after lumbar disc surgery, the robot can be used to help maintain the stability of the lumbar spine, gradually increase the range of motion of the lumbar spine in patients, and avoid muscle atrophy. The WELRR adopts the 4UPS+PS parallel bionic mechanism and sliding mode control scheme based on the linear extended observer. We verified the usability of WELRR through two experiments. In the first experiment, the maximum range of waist movement allowed by the WELRR was verified, which can meet the freedom of movement required by the human body in daily life. In the second experiment, by gathering and comparing the EMG signal of the erector spinae muscle, the use of the WELEE could reduce the EMG signal amplitude. The EMG signal while wearing the WELRR under vertical standing reached the same EMG signal level in a relaxed state, and the effectiveness of lumbar spinal decompression was verified. At present, the WELRR system is undergoing changes and testing prior to clinical trials.