Undulatory Swimming Performance and Body Stiffness Modulation in a Soft Robotic Fish-Inspired Physical Model
Undulatory Swimming Performance and Body Stiffness Modulation in a Soft Robotic Fish-Inspired Physical Model
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DOI：
10.1089/soro.2016.0053
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发表时间：
2017-09-01
期刊：
影响因子：
7.9
通讯作者：
Lauder, George V.
中科院分区：
文献类型：
--
作者：
Jusufi, Ardian;Vogt, Daniel M.;Lauder, George V.
身体的起伏运动是鱼类的主要运动方式，对身体运动学和肌肉活动模式的大量研究为游泳的力学提供了见解。然而，由于无法控制活的、自由游泳的鱼类的肌肉激活，目前还不可能研究诸如双侧肌肉激活程度等关键参数如何影响推进性能。在这篇文章中，我们扩展了以前关于波动推进的被动柔性力学模型的工作，通过在柔性翼片上连接主动控制气动执行器来深入了解波动运动和车身刚度控制的机制。在柔性板的两边各安装了两个柔性执行器，其刚度与鱼体相当。为了研究如何利用双侧收缩来改变游泳过程中的轴向身体僵硬，我们对执行器收缩的相位和频率进行了参数扫描。软气动执行器的推力产生在循环波动频率为0.3~1.2 Hz的循环流动水箱中进行了测试，流速高达28 cm/S。总体来说，该系统在较高的尾拍频率下产生了更多的推力，推力平台在0.8赫兹以上。当激励频率为0.55赫兹时，自行车组的速度为每秒0.8片，相当于13厘米/S。这种主动气动模型能够产生相当大的后缘振幅，最大漂移相当于1.4箔长度，并能产生相当大的推力。在周期的-22%到17%的范围内改变双侧共同收缩的程度，表明推力是最大的，同时的左右激励量类似于周期的3%到6%。当系统暴露在水流中时，对于左右驱动中最对抗性重叠的情况以及引入的最大潜伏期，推力显著减小。该实验平台为研究波动运动学主动控制的水上推进提供了一个软机器人试验台。
Undulatory motion of the body is the dominant mode of locomotion in fishes, and numerous studies of body kinematics and muscle activity patterns have provided insights into the mechanics of swimming. However, it has not been possible to investigate how key parameters such as the extent of bilateral muscle activation affect propulsive performance due to the inability to manipulate muscle activation in live, freely swimming fishes. In this article we extend previous work on passive flexible mechanical models of undulatory propulsion by using actively controlled pneumatic actuators attached to a flexible foil to gain insight into undulatory locomotion and mechanisms for body stiffness control. Two soft actuators were attached on each side of a flexible panel with stiffness comparable to that of a fish body. To study how bilateral contraction can be used to modify axial body stiffness during swimming, we ran a parameter sweep of actuator contraction phasing and frequency. Thrust production by the soft pneumatic actuators was tested at cyclic undulation frequencies ranging from 0.3 to 1.2 Hz in a recirculating flow tank at flow speeds up to 28 cm/s. Overall, this system generated more thrust at higher tail beat frequencies, with a plateau in thrust above 0.8 Hz. Self-propelled speed was found to be 0.8 foil lengths per second or similar to 13 cm/s when actuated at 0.55 Hz. This active pneumatic model is capable of producing substantial trailing edge amplitudes with a maximum excursion equivalent to 1.4 foil lengths, and of generating considerable thrust. Altering the extent of bilateral co-contraction in a range from -22% to 17% of the cycle period showed that thrust was maximized with some amount of simultaneous left-right actuation of similar to 3% to 6% of the cycle period. When the system is exposed to water flow, thrust was substantially reduced for conditions of greatest antagonistic overlap in left-right actuation, and also for the largest latencies introduced. This experimental platform provides a soft robotic testbed for studying aquatic propulsion with active control of undulatory kinematics.