Position solution and kinematic interference analysis of a novel parallel hip-assistive mechanism

In recent years, multiple powered exoskeletons, typically focused on one-DOF (degree of freedom) flexion/extension assistance, have been developed to aid the elderly or patients with hip motion disability. To achieve two-DOF adduction/abduction and flexion/extension assistance, a novel parallel hip-assistive mechanism was proposed, consisting of a waist unit, a leg unit and two parallel driving branches. As the mechanism is connected to the human hip, a human-robot closed chain with three parallel branches is formed. The structure of the parallel assistive mechanism, featuring a bearing-like leg unit prototype to remove the restriction on hip internal/external rotation, was introduced. Subsequently, the mobility assessment of the human-robot closed chain, the position solution of the assistive mechanism and the test approach of branch interference were addressed, with the assumption that the flexible distortions of human bodies are negligible. Finally, the joint motion ranges and branch interference of the mechanism were analyzed, throughout a hip gait cycle. Obtained results indicated that the joint motion ranges are small, with no apparent branch interference, meaning that the proposed parallel mechanism can successfully assist the operation of the hip. Consequently, these results could be used as original design parameters of the assistive mechanism.