HipExo: A Hip Exoskeleton Robot for Load Lifting with Flexible Trunk Linkage Mechanism

This paper proposes a hip exoskeleton robot named HipExo to provide power assistance for the industrial workers during stoop lifting activities. It introduces a hybrid actuator to power the hip joints. The electric motor and transmission is coupled to a spring system that can store biomechanical energy during the descent phase and release the stored energy during the ascent phase of the lifting cycle. Furthermore, the robot is comprised of flexible upper body linkage mechanism capable of adapting to the lumbar curvature and assuming the shape of the trunk. A mathematical model is formulated to estimate the hip torque profile for the stoop lifting cycle. Moreover, a torque control approach was introduced to control the robot according to the motion intentions of the user. The experimental results reveal that HipExo is effective in reducing muscle activity during stoop lifting and it has the potential of alleviating lift-related musculoskeletal disorders.