Variable-Damper Control Using MR Fluid for Lower Back Support Exoskeleton

Even with proper lifting techniques, fatigue can cause many debilitating injuries. Exoskeleton lumbar support devices help prevent these injuries for workers and improve their overall performance. In this article, we present a study on the performance of a semiactive lower back support exoskeleton. The device is powered by a spring–damper mechanism that utilizes a magnetorheological fluid to add a resistive force to the hip joint. The braking force of the device showed a range between 100 and 900 N depending on the compression stroke, coil current, and actuation speed. Muscle activation of the latissimus dorsi, erector spinae, and gluteus maximus was reduced. The analysis based on a biomechanical model showed a power reduction of 40% at the hip joint in the bending phase, and a total reduction of 20% during the entire lifting cycle. The automatic control system using only embedded sensors showed successful and stable functioning but had excessive delays in the activation of the device.