Cable-Driven and Series Elastic Actuation Coupled for a Rigid-Flexible Spine-Hip Assistive Exoskeleton in Stoop-Lifting Event

This article presents a design of an electrically powered spine-hip assistive exoskeleton (SHAE) to relieve back muscle fatigue of industrial workers and prevent back injuries. The rigid-flexible coupling driving realizes the performance of the system in terms of comfort, weight, flexibility, system durability, and industrial feasibility. It uses only two series elastic actuators (SEAs), coupled to drive two hip joints and one bio-inspired spine mechanism. The SEA is realized by the ball screw driving the elastic slider, which is, respectively, transmitted to the spine mechanism and the hip joints in cable driving mechanism and crank-slider mechanism. This device can distribute power to wearer's back and hips during a stoop-lifting event. In the state of lateral bending, axial rotation, and walking of the wearer, it can meet the needs of flexible movement of human body with the advantages of good back driving performance and low impedance. Furthermore, in order to transmit the torque determined by a high-level controller, an SEA force controller is implemented by measuring the elastic displacement of the spring unit installed in the slider. To evaluate the effectiveness of the developed exoskeleton mechanism, we experimentally verified the feasibility of different motion modes. Finally, the effectiveness of SHAE in assisting the waist was verified by collecting and comparing the electromyography signals of the relevant muscles of the waist during stoop-lifting exercise of the subjects with and without wearing the SHAE.