Wearable chairless exoskeleton capable of flexible support to relieve muscle fatigue for industrial workers

Currently, workers who need to maintain specific postures for prolonged periods, such as assemblers, builders, and operators, often suffer from work-related musculoskeletal disorders (WMSDs), resulting in muscle fatigue and joint injuries. Although exoskeleton-assisted technologies have been widely explored to assist workers with posture support, existing chairless exoskeletons cannot reinforce all the joints of the lower extremities at multiple angles or involve bulky additional legs, incapable of agile and flexible support. Here, we develop a wearable chairless exoskeleton that can strengthen the hip, knee, and ankle joints by integrating six magnetorheological (MR) actuators. It is flexible with 5 degrees of freedom (DOFs) on each leg, avoiding unfavorable effects on leg movements and allowing various large-scale, multi-DOF maneuvers. The MR actuators are compact with a high torque density of 126.32 Nm/kg. The actuator, with a power consumption of 7.0 W, can provide a damping resistance torque of 120 Nm to lock the joint at any angle. Therefore, the chairless exoskeleton can provide stable support for the wearer in a wide range of postures. We modeled the human-exoskeleton system and theoretically analyzed the support force required for posture maintenance. Moreover, the safety margins for the hip, knee, and ankle joints in our configuration are 41.54%, 42.89%, and 39.51%, respectively, enhancing both safety and reliability for the user by protecting against potential overloading or instability. The individual-wearing experiments and demonstrations exhibited the exoskeleton’s capabilities, including an average reduction of 74.24% in muscle electromyographic (EMG) and enhanced endurance during posture sustain tasks.