Continuum robots exhibit promising adaptability and dexterity for soft manipulation due to their intrinsic compliance. However, this compliance may lead to challenges in modeling as well as positioning and loading. In this paper, a virtual work-based static model is established to describe the deformation and mechanics of continuum robots with a generic rod-driven structure, taking the geometric constraint of the drive rods into account. Following this, this paper presents a novel variable stiffness mechanism powered by a set of embedded Shape Memory Alloy (SMA) springs, which can make the drive rods become ‘locked’ on the body structure with different configurations. The resulting effects of variable stiffness are then presented in the static model by introducing tensions of the SMA and friction on the rods. Compared with conventional models, there is no need to predefine the actuation forces of the drive rods; instead, actuation displacements are used in this new mechanism system with stiffness being regulated. As a result, the phenomenon that the continuum robot can exhibit an S-shaped curve when subject to single-directional forces is observed and analyzed. Simulations and experiments demonstrated that the presented mechanism has stiffness variation of over 287% and further demonstrated that the mechanism and its model are achievable with good accuracy, such that the ratio of positioning error is less than 2.23% at the robot end-effector to the robot length.

中文翻译：

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基于几何约束的形状记忆合金启动变刚度连续体机器人建模与分析

连续体机器人由于其内在的顺应性，在软操作方面表现出良好的适应性和灵巧性。然而，这种合规性可能会导致建模以及定位和加载方面的挑战。本文建立了一个基于虚拟工作的静态模型来描述具有通用杆驱动结构的连续体机器人的变形和力学，同时考虑了驱动杆的几何约束。在此之后，本文提出了一种由一组嵌入式形状记忆合金 (SMA) 弹簧提供动力的新型可变刚度机构，它可以使驱动杆“锁定”在具有不同配置的车身结构上。然后通过引入 SMA 的张力和杆上的摩擦力，在静态模型中呈现可变刚度的结果。与传统机型相比，无需预先定义驱动杆的驱动力；相反，在这个新的机械系统中使用了致动位移，并调节了刚度。因此，观察和分析了连续体机器人在受到单向力时会呈现 S 形曲线的现象。仿真和实验表明，所提出的机构具有超过 287% 的刚度变化，并进一步证明该机构及其模型具有良好的精度，使得机器人末端执行器的定位误差比小于 2.23%。机器人长度。观察和分析了连续体机器人在受到单向力作用时可以呈现S形曲线的现象。仿真和实验表明，所提出的机构具有超过 287% 的刚度变化，并进一步证明该机构及其模型具有良好的精度，使得机器人末端执行器的定位误差比小于 2.23%。机器人长度。观察和分析了连续体机器人在受到单向力作用时可以呈现S形曲线的现象。仿真和实验表明，所提出的机构具有超过 287% 的刚度变化，并进一步证明该机构及其模型具有良好的精度，使得机器人末端执行器的定位误差比小于 2.23%。机器人长度。