One of the main challenges for the elderly is insufficient lower limb strength during sit-to-stand movement, which may be improved by supporting the joint externally. Existing lower extremity exoskeletons use perfect revolute joints as knee joints, which do not match with human joint biomechanics. They also require a complex control system to produce the required torque at the corresponding joint angle. In this study, a knee support device using four-bar joint mechanism and hydraulic artificial muscle (HAM) was designed. A previously proposed four-bar linkage joint was modified to accommodate the HAM. In addition, the Angled Bar was proposed to exploit HAM’s force-contraction relationship to generate the desired torque at the corresponding angle only by applying constant hydraulic pressure without the use of a complex control system. The device was able to generate a maximum output of 126.55 Nm torque at 100$$^{\circ }$$ knee joint angle during loading and 70.69 Nm torque at 100$$^{\circ }$$ during unloading at 3 MPa pressure. The root-mean-square error of the knee extension torque curve was 13.01 Nm. Experiment with a healthy participant showed significant reduction in muscle activity with the assist from the device. The maximum processed EMG signal with and without assist were 52.10 and 20.93 $${\upmu \mathrm{V}}$$, respectively.

中文翻译：

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基于四连杆和液压人工肌肉的膝关节支撑装置设计

老年人的主要挑战之一是从坐到站运动期间下肢力量不足，这可以通过在外部支撑关节来改善。现有的下肢外骨骼使用完美的旋转关节作为膝关节，这与人体关节的生物力学不符。他们还需要复杂的控制系统以在相应的接头角度处产生所需的扭矩。在这项研究中，设计了一种使用四连杆机构和液压人工肌肉（HAM）的膝盖支撑装置。先前提出的四连杆联动接头已进行了改装，以适应HAM。另外，提出了斜杆以利用HAM的力-收缩关系仅通过施加恒定的液压压力而在不使用复杂的控制系统的情况下以相应的角度来产生期望的扭矩。该设备在加载过程中在膝关节角度为100 $$ ^ {\ circ} $$时能够产生最大输出126.55 Nm扭矩，在3 MPa压力下卸载时能够以100 $$ ^ {\ circ} $$产生最大输出70.69 Nm扭矩。膝盖伸展扭矩曲线的均方根误差为13.01 Nm。健康参与者的实验显示，借助设备，肌肉活动明显减少。带有和不带有辅助的最大已处理EMG信号分别为52.10和20.93 $$ {\ upmu \ mathrm {V}} $$。健康参与者的实验显示，借助设备，肌肉活动明显减少。带有和不带有辅助的最大已处理EMG信号分别为52.10和20.93 $$ {\ upmu \ mathrm {V}} $$。健康参与者的实验显示，借助设备，肌肉活动明显减少。带有和不带有辅助的最大已处理EMG信号分别为52.10和20.93 $$ {\ upmu \ mathrm {V}} $$。