A Bianisotropic Damper Based on Magnetorheological Fluid for a Quasi-Passive Load-Bearing Exoskeleton

Load-bearing exoskeletons are expected to have high potential for use in military, fire-fighting, and logistics applications. Passive exoskeletons are more advantages owing to their light weight and long endurance. The load-bearing ability of such exoskeletons depends on the mechanical performance of joints, and reasonable output in knee joint is helpful to improve the load-bearing ability. In this article, to improve the load-bearing performance of the lower limb exoskeleton, a novel bianisotropic damper based on a magnetorheological fluid (BaDMr) is proposed, which is of bidirectional anisotropy in damping via a double-channel structure design to match the needed torque in exoskeleton knee during human walking with heavy load. It is of compact structure, light weight, and large torque output range. The ability of damping adjustment and load-bearing of the proposed system were verified via numerical simulation and a series of physical experiments. The results confirmed that BaDMr has a hysteresis rate of 6.42%, an average step response time of 16.06 ms, and torque tracking accuracy with a 5.3% root-mean-square error of the desire torque. In addition, an experimental platform of lower limb quasi-passive load-bearing exoskeleton was built to investigate the performance of BaDMr in real application scenarios. The load-bearing experiments verified that the exoskeleton could significantly reduce the impact of load on the wearer.