This article proposes a novel type of series-parallel lower extremity exoskeleton driven by hydraulic actuators. Each leg of the exoskeleton has six DOFs, which can walk like human and carry heavy loads. A mapping from the positions of human lower extremity joints to the exoskeleton joints was established. Based on Kane's method, the inverse dynamic model of the exoskeleton was conducted. Finally, the exoskeleton humanoid gaits of level walking, ascent, descent, level walking with different loads and speed were simulated, and the required driving torques and power were obtained. These performance analyses provide a basis to the design of the control law and the estimation of the hydraulic actuator parameters for the exoskeleton.
An innovative lower extremity exoskeleton, SJTU-EX, is demonstrated in Shanghai JiaoTong University, which mainly aims to help soldiers and workers to support a payload in motion. This paper summarizes the mechanical design of SJTU-EX. Each pseudo-anthropomorphic leg of SJTU-EX has four active joints and two passive joints, and the joint ranges are optimized in consideration of both safety factors and the realization of typical motions. Springs are applied in the leg to eliminate the effect of gravity. The results of dynamic simulations are used to determine the actuated joints and the passive joints. Novel Hy-Mo actuators are introduced for SJTU-EX and the layout of the actuator for Diamond Side 2 is described in detail as a design example.
A novel type of lower extremity exoskeleton with series-parallel topology was described. Position analysis of a simplified leg was conducted to provide a basis of the kinematic accuracy reliability. Considering both assembly-machining errors and driving errors, the fuzzy reliability of kinematic accuracy was obtained based on the fuzzy probability theory. With a set of optimized length parameters and joint ranges of motion given, the fuzzy reliability of space distribution and the average fuzzy reliability were respectively calculated and shown in figures. These analyses of kinematic accuracy reliability provide a unique method to judge, analyze, and design exoskeleton mechanisms.
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