Abstract Kinematic mismatch between exoskeletons and human body results in excess internal forces/torques and hence discomfort as well as increase the power consumption. The connection stiffness has been shown to have potentials for minimizing the kinematic mismatch effects. However, realization of a desired stiffness in the connection element seems difficult if not impractical. In this work, adding controlled backlash to the exoskeleton-body connection is investigated as a possible solution for the kinematic mismatch challenge. A stiffness model which includes backlash parameters was formulated and identified experimentally using three male subjects on a typical lower extremity exoskeleton. A performance index which includes tracking error and user's comfort was calculated on a normal gait cycle. The impact of the backlash parameters including: type, direction and range was analyzed in detail. The impact of adding a tuned backlash to the shank is significant while it is negligible for the thigh connection. The highest performance improvement was obtained by cylindrical backlash added to the shank axial direction (97%) with a range of 15∘ and 13 mm. The proposed method and results are believed to be directly applicable to the optimal design of robotic exoskeletons.

中文翻译：

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增加连接元件的间隙可以提高机器人外骨骼的性能

摘要 外骨骼与人体的运动学失配导致内力/扭矩过大，从而产生不适感，并增加功耗。连接刚度已被证明具有最小化运动失配效应的潜力。然而，即使不是不切实际，在连接元件中实现所需刚度似乎也很困难。在这项工作中，研究了为外骨骼-身体连接添加受控反冲作为运动失配挑战的可能解决方案。使用三名男性受试者在典型的下肢外骨骼上制定并通过实验确定了包括反冲参数的刚度模型。在正常步态周期计算包括跟踪误差和用户舒适度的性能指数。详细分析了背隙参数的影响，包括：类型、方向和范围。对小腿添加调谐后冲的影响是显着的，而对大腿连接则可以忽略不计。最大的性能改进是通过在柄轴方向上增加圆柱间隙 (97%) 获得的，范围为 15∘ 和 13 mm。所提出的方法和结果被认为可直接应用于机器人外骨骼的优化设计。