Adaptive design and control of a robot-assisted lower back exoskeletal spine system

Abstract

In order to help elder people who suffer from lower back pain caused by lower spine degeneration, a novel kind of robot-assisted exoskeleton spine was designed. Itwasmainly applied to lift their upper bodies for assistingmovements and reducing backache during walking. The aim of this system was to control an elastically actuated motor to provide extra torques on a user’s hip by following the gaits in locomotion. And the whole exoskeletal spine mechanism (exo-spine) has been built of flexible material and fixed on an artificial pelvis. Thanks to the use of a cablepulley-spring structure the torque applied to the hip is greatly amplified and would eventually affect the deformation of exo-spine, so that an auxiliary force is generated on the lower back to support user’s spine during the movements. Although the overall robot-assisted system was easily imaged and designed, its intrinsic complexity needed careful analysis, because the actuating process becomes highly nonlinear and noisy when compliant movements are demanded to mimic human performances in locomotion. Therefore, some appropriate assumptions were introduced, and to enhance the robustness of system, an adaptive controller was designed by applying Lyapunov Stability Theory. Finally, the correctness and feasibility of our proposed system were tested and estimated through a set of experimental simulations.