Screw-based locomotion is a robust method of locomotion across a wide range of media including water, sand, and gravel. A challenge with screws is their significant number of impactful design parameters that affect locomotion performance. One crucial parameter is the angle of attack (also called the lead angle), which has been shown to significantly impact the performance of screw propellers in terms of traveling velocity, force produced, degree of slip, and sinkage. As a result, the optimal design choice may vary significantly depending on application and mission objectives. In this work, we present the Novel Actuating Screw Unit (NASU). It is the first screw-based propulsion design that enables dynamic reconfiguration of the angle of attack for optimized locomotion across multiple media and use cases. The design is inspired by the kresling unit, a mechanism from origami robotics, and the angle of attack is adjusted with a linear actuator. In contrast, the entire unit is spun on its axis to generate propulsion. NASU is integrated into a mobile test bed and experiments are conducted in various media including gravel, grass, and sand. Our experiment results indicate a trade-off between locomotive efficiency and velocity exists regarding angle of attack, and the proposed design is a promising direction for reconfigurable screws by allowing control to optimize for efficiency or velocity.

翻译：螺旋推进是一种在包括水、沙、砾石等多种介质中稳健的移动方式。螺旋推进的挑战在于其影响运动性能的设计参数数量众多且影响显著。其中一个关键参数是攻角（也称导程角），已被证明对螺旋推进器在行进速度、产生的力、滑移程度和沉陷量方面的性能具有显著影响。因此，最优设计选择可能因应用场景和任务目标的不同而存在显著差异。本文提出了新型驱动螺旋单元（NASU）。这是首个能够动态重构攻角以优化多介质和多用例运动的螺旋推进设计。该设计受折纸机器人中的克雷斯林单元启发，并采用线性执行器调节攻角；与此同时，整个单元绕其轴线旋转以产生推进力。NASU被集成到移动测试平台中，并在砾石、草地和沙地等多种介质中进行了实验。实验结果表明，攻角在运动效率与速度之间存在权衡关系，且该设计通过允许控制以优化效率或速度，为可重构螺旋推进指明了有前景的方向。