Soft robots take advantage of rich nonlinear dynamics and large degrees of freedom to perform actions often by novel means beyond the capability of conventional rigid robots. Nevertheless, there are considerable challenges in analysis, design, and optimization of soft robots due to their complex behaviors. This is especially true for soft robotic swimmers whose dynamics are determined by highly nonlinear fluid-structure interactions. We present a holistic computational framework that employs a multi-objective evolutionary method to optimize feedback controllers for maneuvers of a soft robotic fish under artificial muscle actuation. The resultant fluid-structure interactions are fully solved by using a novel fictitious domain/active strain method. In particular, we consider a two-dimensional elastic plate with finite thickness, subjected to active contractile strains on both sides of the body. Compared to the conventional approaches that require specifying the entire-body curvature variation, we demonstrate that imposing contractile active strains locally can produce various swimming gaits, such as forwarding swimming and turning, using far fewer control parameters. The parameters of a pair of proportional-integral-derivative (PID) controllers, used to control the amplitude and the bias of the active strains, respectively, are optimized for tracking a moving target involving different trajectories and Reynolds numbers, with three objectives, tracking error, cost of transport, and elastic strain energy. The resulting Pareto fronts of the multi-objective optimization problem reveal the correlation and trade-off among the objectives and offer key insight into the design and control of soft swimmers.

中文翻译：

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基于CFD的多机器人控制器的优化，适用于具有肌肉样动作的软机器人鱼。

软机器人利用丰富的非线性动力学和较大的自由度，经常通过新颖的方法来执行动作，而这些动作超出了常规刚性机器人的能力。然而，由于软机器人的复杂行为，在分析，设计和优化方面仍然存在相当大的挑战。对于其动力由高度非线性的流体-结构相互作用决定的软机器人游泳者而言，尤其如此。我们提出了一种整体的计算框架，该框架采用了多目标进化方法来优化在人工肌肉驱动下对软机器人鱼的操纵的反馈控制器。通过使用一种新型的虚拟域/活动应变方法，完全解决了所得的流体-结构相互作用。特别地，我们考虑具有有限厚度的二维弹性板，在身体两侧承受主动收缩力。与需要指定全身曲率变化的常规方法相比，我们证明了在局部施加可收缩的活动应变可以使用少得多的控制参数来产生各种游泳步态，例如向前游泳和转弯。分别用于控制活动应变的振幅和偏置的一对比例积分微分（PID）控制器的参数经过优化，可跟踪涉及不同轨迹和雷诺数的运动目标，并具有三个目标，即跟踪错误，运输成本和弹性应变能。