Flexible manipulators offer significant advantages over traditional rigid manipulators in minimally invasive surgery, because they can flexibly navigate around obstacles and pass cramped or tortuous paths. However, due to the inherent low stiffness, the ability to control/obtain higher stiffness when required remains to be further explored. In this article, we propose a flexible manipulator that exploits the phase transformation property of low-melting-point alloy to hydraulically drive and change the stiffness by heating and cooling. A prototype was fabricated, and experiments were conducted to evaluate the motion characteristics, stiffness performance, and rigid-flexible transition efficiency. The experimental results demonstrate that the proposed manipulator can freely adjust heading direction in the three-dimensional space. The experimental results also indicate that it took 9.2–10.3 s for the manipulator to transform from a rigid state to a flexible state and 15.4 s to transform from a flexible state to a rigid state. The lateral stiffness and flexural stiffness of the manipulator were 95.54 and 372.1 Ncm² in the rigid state and 7.26 and 0.78 Ncm² in the flexible state. The gain of the lateral stiffness and flexural stiffness was 13.15 and 477.05, respectively. In the rigid state, the ultimate force without shape deformation was more than 0.98 N in the straight condition (0°) and 1.36 N in the bending condition (90°). By assembling flexible surgical tools, the manipulator can enrich the diagnosis or treatment functions, which demonstrated the potential clinical value of the proposed manipulator.

中文翻译：

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具有低熔点合金驱动和可变刚度的柔性机械手

与传统的刚性机械手相比，柔性机械手在微创手术中具有显着优势，因为它们可以灵活地绕过障碍物并通过狭窄或曲折的路径。然而，由于固有的低刚度，在需要时控制/获得更高刚度的能力仍有待进一步探索。在本文中，我们提出了一种柔性机械手，该机械手利用低熔点合金的相变特性来液压驱动并通过加热和冷却来改变刚度。制作了原型，并进行了实验以评估运动特性、刚度性能和刚柔过渡效率。实验结果表明，所提出的机械臂可以在三维空间中自由调整航向。实验结果还表明，机械臂从刚性状态转变为柔性状态需要 9.2-10.3 s，从柔性状态转变为刚性状态需要 15.4 s。机械手的横向刚度和弯曲刚度分别为95.54和372.1 Ncm²在刚性状态和 7.26 和 0.78 Ncm ²在柔性状态。横向刚度和弯曲刚度的增益分别为 13.15 和 477.05。在刚性状态下，没有形状变形的极限力在直线状态（0°）下大于 0.98 N，在弯曲状态下（90°）大于 1.36 N。通过组装灵活的手术工具，该机械手可以丰富诊断或治疗功能，这证明了所提出的机械手的潜在临床价值。