The bending stiffness modulation mechanism for soft grippers has gained considerable attention to improve grasping versatility, capacity, and stability. However, lateral stability is usually ignored or hard to achieve at the same time with good bending stiffness modulation performance. Therefore, this article presents a bioinspired bidirectional stiffening soft actuator (BISA), enabling compliant and stable performance. BISA combines the air tendon actuation (ATA) and a bone-like structure (BLS). The ATA is the main actuation of the BISA, and the bending stiffness can be modulated with a maximum stiffness of about 0.7 N/mm and a maximum magnification of three times when the bending angle is 45°. Inspired by the morphological structure of the phalanx, the lateral stiffness can be modulated by changing the pulling force of the BLS. The actuator with BLSs can improve the lateral stiffness by about 3.9 times compared to the one without BLSs. The maximum lateral stiffness can reach 0.46 N/mm. And the lateral stiffness can be modulated by decoupling about 1.3 times (e.g., from 0.35 to 0.46 N/mm when the bending angle is 45°). The test results show that the influence of the rigid structures on bending is small with about 1.5 mm maximum position errors of the distal point of the actuator in different pulling forces. The advantages brought by the proposed method enable versatile four-finger grasping. The performance of this gripper is characterized and demonstrated on multiscale, multiweight, and multimodal grasping tasks.

中文翻译：

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仿生双向硬化软执行器可实现多功能且坚固的抓取。


软夹持器的弯曲刚度调制机制在提高夹持多功能性、容量和稳定性方面受到了广泛关注。然而，横向稳定性通常被忽略或难以同时实现良好的弯曲刚度调制性能。因此，本文提出了一种仿生双向硬化软执行器（BISA），可实现合规且稳定的性能。 BISA 结合了空气腱驱动 (ATA) 和骨样结构 (BLS)。 ATA是BISA的主要驱动方式，弯曲刚度可调节，弯曲角度为45°时，最大刚度约为0.7 N/mm，最大放大倍数为3倍。受指骨形态结构的启发，可以通过改变 BLS 的拉力来调节侧向刚度。与不带 BLS 的执行器相比，带 BLS 的执行器可将横向刚度提高约 3.9 倍。最大横向刚度可达0.46 N/mm。并且横向刚度可以通过解耦调节约1.3倍（例如，当弯曲角度为45°时，从0.35到0.46N/mm）。测试结果表明，刚性结构对弯曲的影响较小，不同拉力下执行器远端点的最大位置误差约为1.5 mm。该方法带来的优点使得多功能四指抓取成为可能。该夹具的性能在多尺度、多重量和多模式抓取任务中进行了表征和演示。