Variable Stiffness Spring Actuators for Low-Energy-Cost Human Augmentation
Variable Stiffness Spring Actuators for Low-Energy-Cost Human Augmentation
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DOI：
10.1109/tro.2019.2929686
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发表时间：
2019-12-01
影响因子：
7.8
通讯作者：
Hogan, Neville
中科院分区：
文献类型：
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作者：
Braun, David J.;Chalvet, Vincent;Hogan, Neville
理论研究表明，实验证据证实，通过共同激活的拮抗肌肉来维持和改变人体关节刚度在代谢上是昂贵的，即使肌肉不进行净机械功。基于这一观察，我们假设通过与人体关节并行操作的致动器可以实现有效的人体增强，即使这些致动器只补充关节刚度而不做净机械功。在本文中，我们提出了一个原型变长叶弹簧驱动器能够大范围的刚度调制。该驱动器的主要特点是，即使在大的输出偏转情况下，通过保持驱动电机上的力低，它也能提供本质上低能量成本的刚度调制。可变刚度执行器使用两个电机来提供刚度和平衡位置调制，因为它们被设计为做净机械功。所提出的执行器在概念上与可变刚度执行器不同，因为首先，它使用单个电机仅提供刚度调制，其次，它不提供平衡位置调制，第三，除非外部加载，否则它不能做净机械功。使用该驱动器，我们展示了在具有挑战性的姿势稳定和负重任务的人机协作中刚度增强。我们的研究结果表明，所提出的执行器可以通过低能量成本恢复或扩展生物系统的功能来补充生物系统，可变刚度弹簧执行器可以通过不做或做有限的机械功来有效地增强人类。
Theoretical studies suggest and experimental evidence confirms that maintaining and changing human joint stiffness by coactivated antagonistic muscles are metabolically expensive, even if muscles do not perform net mechanical work. Based on this observation, we posit that effective human augmentation can be achieved by actuators operated in parallel to human joints, even if these actuators only supplement joint stiffness without doing net mechanical work. In this article, we present a prototype variable-length leaf-spring actuator capable of large-range stiffness modulation. The key feature of the actuator is that it provides intrinsically low-energy-cost stiffness modulation even for large output deflection, by keeping the force on the driving motor low. Variable stiffness actuators use two motors to provide both stiffness and equilibrium position modulation as they are designed to do net mechanical work. The proposed actuator conceptually differs from variable stiffness actuators because first, it uses a single motor to only provide stiffness modulation, second, it does not provide equilibrium position modulation, and third, unless externally loaded, it cannot do net mechanical work. Using this actuator, we demonstrate stiffness augmentation during human-machine collaboration in challenging postural stabilization and weight-bearing tasks. Our results indicate that the proposed actuator can be used to complement a biological system by restoring or extending its functionality with low energy cost, and that variable stiffness spring actuators could effectively augment humans by doing no or a limited amount of mechanical work.