IEEE Trans Neural Syst Rehabil Eng. 2023;31:2497-2506. doi: 10.1109/TNSRE.2023.3276424. Epub 2023 Jun 1.
The development of assistive lower-limb exoskeletons can be time-consuming. Testing prototype medical devices on vulnerable populations such as children also has safety concerns. Mechanical phantoms replicating the lower-limb kinematics provide an alternative for the fast validation and iteration of exoskeletons. However, most phantoms treat the limbs as rigid bodies and fail to capture soft tissue deformation at the human/exoskeleton interface. Human soft tissue can absorb and dissipate energy when compressed, leading to a mismatch between simulated and human exoskeleton testing outcomes. We have developed a methodology for quickly testing and validating the performance of knee exoskeletons using a mechanical phantom capable of emulating knee kinematics soft-tissue deformation of the lower-limb. Our phantom consisted of 3D-printed bones surrounded by ballistic gel. A motorized hexapod moved the knee to follow a walking trajectory. A custom inverse dynamics model estimated the knee assistance moment from marker and load cell data. We applied this methodology to quantify the effects of soft-tissue deformation on exoskeleton assistance by loading the phantom knee with a torsional spring exoskeleton interfacing and bypassing the ballistic gel. We found that including soft-tissue deformation led to a lower knee assistance moment and stiffness. Some but not all of this difference could be explained by the deflection of the exoskeleton relative to the knee angle, suggesting energy absorption within soft tissue. The direct measurements of exoskeleton assistance provide insight into increasing the assistive moment transmission efficacy. The phantom provided a relatively accurate framework for knee exoskeleton testing, aiding future exoskeleton design.
辅助下肢外骨骼的开发可能需要很长时间。在儿童等弱势群体身上测试原型医疗设备也存在安全问题。模拟下肢运动学的机械仿体为外骨骼的快速验证和迭代提供了一种替代方法。然而，大多数仿体将肢体视为刚体，无法捕捉到人/外骨骼界面处的软组织变形。人体软组织在受压时可以吸收和耗散能量，导致模拟和人体外骨骼测试结果之间不匹配。我们已经开发了一种使用能够模拟下肢膝关节运动学和软组织变形的机械仿体快速测试和验证膝关节外骨骼性能的方法。我们的仿体由 3D 打印的骨骼和弹道凝胶组成。一个电动六足机器人移动膝关节以跟随步行轨迹。一个定制的逆动力学模型根据标记和负载细胞数据估计膝关节辅助力矩。我们通过在仿体膝关节上加载扭转弹簧外骨骼接口并绕过弹道凝胶来加载仿体膝关节，应用这种方法来量化软组织变形对外骨骼辅助的影响。我们发现，包括软组织变形在内，会导致膝关节辅助力矩和刚度降低。这种差异的一部分但不是全部可以用外骨骼相对于膝关节角度的偏转来解释，这表明软组织内部有能量吸收。对外骨骼辅助的直接测量提供了增加辅助力矩传递效率的深入了解。该仿体为膝关节外骨骼测试提供了一个相对准确的框架，有助于未来的外骨骼设计。
