###### Abstract
Experimental results demonstrated that the variable stiffness backbone enhanced the robot's rigidity, minimized twisting issues, and improved the efficiency of bending motions, particularly at the robot's tip. This design offers potential improvements in control precision and adaptability in robotic applications requiring dexterous and compliant manipulation. However, the use of flexible springs increases the risk of buckling under excessive force along the backbone, which can compromise the robot's stability and performance. Furthermore, while the design incorporates variable stiffness to improve control, this feature requires careful calibration and increases the complexity of the system. A comprehensive mechanical model for a continuum robot, inspired by an elephant's trunk, has been developed to predict the robot's deformation under various conditions [3]. The robot's modular structure incorporates adjustable stiffness across different segments, enabling adaptability to diverse tasks and environments. This adaptability is achieved through preprogrammable stiffness, which allows the robot to perform complex movements and adjust to varying curvature scenarios. Despite its versatility, the system's complexity poses a significant challenge, as the precise control of stiffness across multiple segments demands intricate coordination between the hardware and software components. Figure 1: (**a**) A photograph of an elephant with its trunk in a natural environment. (**b**) Dorsal view of the complete trunk specimen. (**c**) Left hemi-trunk before staining and scanning [1]. The design and kinematic analysis of a bioinspired elephant trunk robot with a variable diameter showed that it offers significant advancements in the dexterity and adaptability of continuum robots [4]. The robot incorporates a soft motion mechanism combined with a rigid variable-diameter mechanism, enabling it to adjust its radial size and optimize performance for diverse tasks. This innovative design enhances the robot's compliance, stiffness, and workspace versatility, allowing it to perform a wide range of motions with high precision. The kinematic model, which integrates both soft and rigid elements, was validated through simulations and experiments, demonstrating the robot's capability to effectively adapt its shape and stiffness for complex manipulation tasks. Despite these advantages, the current design's ability to change diameter is restricted to two discrete states, and the added weight of the mechanism may limit performance in certain applications. Future efforts will focus on developing a prototype with continuous diameter adjustment and minimizing the robot's weight to further enhance its functionality. In line with the advancements in bioinspired robotics, a variable-curvature elephant trunk robot (ETR) has been developed for applications in nuclear maintenance, particularly within the narrow and confined spaces of the China Fusion Engineering Test Reactor [5]. The ETR incorporates a miniaturized, lightweight design that balances flexibility and load-bearing capabilities, allowing it to perform precise inspection and maintenance tasks while maintaining high positional accuracy. Its kinematic model, developed using the Denavit-Hartenberg method, and trajectory-tracking control methods, including end-traction, discrete path, and base-fixed algorithms, were rigorously tested through simulations to validate its structural and motion performance. These control strategies enable the ETR to efficiently navigate complex trajectories, demonstrating the feasibility of deploying continuum robots in challenging environments such as vacuum chambers. This work highlights the potential for bioinspired designs to extend continuum robotics applications beyond traditional domains. Building upon the inspiration derived from the physical intelligence of an elephant's trunk, a recent study proposed a biomimetic soft robot with preprogrammable localized stiffness [6; 7].