Ideas

基本杆组（Assur group），又称阿苏尔杆组，是在机械机构中增减后不影响整体自由度的最小构件与运动副组合，其基本特征为自由度为零，属于机械原理学科中的基础概念，主要应用于机械机构分析。该杆组按内部运动副数量分为Ⅱ级、Ⅲ级、Ⅳ级等级别，其中Ⅱ级为最低级别。根据机构组成原理，机构可通过将基本杆组依次连接原动件与机架构建而成。确定机构级别时需拆解所含杆组，优先从远离原动件的构件处尝试拆分低级别杆组，拆分后需确保剩余部分仍为完整机构且自由度不变。

In kinematics, an Assur group is a kinematic chain with zero degree of mobility, which added or subtracted from a mechanism do not alter its original number of degrees of freedom. They have been first described by the Russian engineer Leonid Assur (1878–1920) in 1914.[2][3]

https://en.wikipedia.org/wiki/Assur_group

正六边形扭曲折纸单元折痕图与折叠样式

60度棱形扭曲折纸单元折痕图与折叠样式

正方形扭曲折纸单元折痕图与折叠样式

三角形扭曲折纸单元折痕图与折叠样式

混合正方形扭曲折纸单元折痕图与折叠样式

(FYP) Tee YH

Automated discovery of reprogrammable nonlinear dynamic metamaterials
Nature Materials volume 23, pages1486–1494 (2024)

Harnessing the rich nonlinear dynamics of highly deformable materials has the potential to unlock the next generation of functional smart materials and devices. However, unlocking such potential requires effective strategies to spatially engineer material architectures within the nonlinear dynamic regime. Here we introduce an inverse-design framework to discover flexible mechanical metamaterials with a target nonlinear dynamic response. The desired dynamic task is encoded via optimal tuning of the full-scale metamaterial geometry through an inverse-design approach powered by a fully differentiable simulation environment. By deploying such a strategy, mechanical metamaterials are tailored for energy focusing, energy splitting, dynamic protection and nonlinear motion conversion. Furthermore, our design framework can be expanded to automatically discover reprogrammable architectures capable of switching between different dynamic tasks. For instance, we encode two strongly competing tasks—energy focusing and dynamic protection—within a single architecture, using static precompression to switch between these behaviours. The discovered designs are physically realized and experimentally tested, demonstrating the robustness of the engineered tasks. Our approach opens an untapped avenue towards designer materials with tailored robotic-like reprogrammable functionalities.

自动发现可重编程的
非线性动态超材料

柔性超材料在非线性波的控制方面具有巨大潜力，例如它们可以通过大变形和不稳定性，实现单向信号传播；在耗散环境下实现长距离传播和进行冲击缓冲。然而，目前对非线性超材料的研究仍处于早期阶段，大多数设计依赖周期性结构，这限制了对能量流动的时空控制能力。而本研究希望通过自动化设计方法解锁非线性动态行为的复杂调控，以实现更加智能化、可重编程的机械超材料。
哈佛大学Katia Bertoldi团队提出了一种反向设计框架，用于发现具有特定非线性动态响应的柔性机械超材料。该框架通过全可微模拟环境支持的反向设计方法，对超材料的整体几何结构进行优化调控，从而编码特定的动态任务。采用这一策略，所设计的机械超材料可实现能量聚焦、能量分裂、动态防护和非线性运动转换等功能。此外，本研究的设计框架还可以扩展，以自动发现可重编程结构，使其能够在不同的动态任务之间切换。例如，本研究在同一结构内编码两种相互竞争的任务——能量聚焦与动态防护，并通过静态预压在这两种功能之间切换。
本研究发现的设计方案已通过物理制造和实验测试，结果表明所设计的动态任务具有较高的鲁棒性。该研究为开发具有类似机器人可重编程功能的定制化智能材料开辟了一条新的路径。