Abstract
Improper manipulation of heavy objects can result in hard stresses (tension, compression and shear) throughout the human body parts, especially in the low-back spine. Biomechanics specialists state that injuries that occur in this area may address muscle tissue, joint tissues and intervertebral disc tissues. The effect of a carried load on kinematics and kinetics of body’s lower extremity is significant. Besides of labor protection rules and interventions designed to reduce and avoid injuries, powered wearable exoskeletons have been proposed to amplify human capabilities. The paper regards three significant issues related to exoskeletons: biomechanical modeling, actuation, and multi-level control strategies. Three modalities to get optimal performance of wearable robots are hereby summarized: (i) minimization of interaction force wrench by using direct/indirect force control strategies, (ii) modification of reference trajectory to compensate for unwanted interaction force wrench, and (iii) adding the power assist rate such that zero impedance at interaction attachments is guaranteed. To accomplish these points, most proposed control strategies consist of three levels of control: high-level control, responsible for capturing human movement intention; mid-level control for regulation of divisions of the gait cycle; and low-level control for stabilization of the coupled motion.
Published Version
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