并联索驱动助力外骨骼具有与人体兼容性好、运动范围大、自由度多等优点，但往往需要多个电机驱动多根绳索，增大了驱动结构的重量和能耗。以往的设计中无法实现在减少电机个数的同时实现多绳索的力控与多自由度的助力。该文提出一种基于欠驱动并联索机构的肩关节助力外骨骼，采用凸轮和弹簧来实现搬运工作时肩关节的三自由度助力。根据给定的手臂动作，进行运动学、静力学建模与绳索排布优化，并通过设计凸轮的轮廓，仅采用1个电机就实现多根绳索的不同输出速度，并分析和仿真了电机旋转角度与各绳索索力之间的肩关节三自由度助力关系。实验结果表明电机旋转角度与索力对应关系准确，验证了该欠驱动机构用于解决多绳索与多自由度力控问题的可行性。
Parallel cable-driven exoskeletons for motion assistance have the advantages of good compatibility with the human body, large range of motion, and many degrees of freedom. However, it often requires multiple motors to drive multiple cables, increasing the weight and energy consumption of the actuator. In the previous design, it was impossible to reduce the number of motors while realizing the multi-cable force control and multi-degree-of-freedom assistance. This paper proposes an exoskeleton for shoulder joint assistance based on an underactuated parallel cable mechanism, utilizing cams and springs to realize the three-degree-of-freedom assistance of the shoulder joint. According to a given action of the arm, this research conducts kinematics modeling, static modeling, cable arrangement optimization and cam profile designing. As a result, only one motor is used to achieve the different output speeds required by multiple cables. The analysis and simulation of the relationship between the rotation angle of the motor and the force of each cable in accordance with the three-degree-of-freedom assisting relationship of the shoulder joint were done. Results show that the corresponding relationship between the motor rotation angle and the cable force is accurate, verifying the feasibility of the under-driven mechanism for multi-cable and multi-degree-of-freedom force control.
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