Mechanical modeling and experimental analysis of a hydraulically driven underwater soft twisted tower

Abstract Origami-inspired twisted tower structures present a novel paradigm for designing compliant and reconfigurable mechanisms with high telescopic ratios. In this work, we introduce and investigate a hydraulically actuated underwater soft twisted tower mechanism derived from origami design principles. A quasi-static mechanical model is formulated based on the hyperelastic constitutive behavior of the soft material. To account for the effects of the underwater environment, a nonlinear dynamic model is further established within the Euler–Lagrange framework. Finite element simulations and experimental analyses are conducted for parameter identification and model validation. Results from tensile tests confirm that the nonlinear material response is well characterized by the Yeoh model. The quasi-static analysis reveals that the tensile-type twisted tower configuration provides superior stiffness and stability compared to its compression-type counterpart. After model derivation and parameter calibration, the prediction error is constrained within a maximum of 2.01 mm. This study offers new insights into the nonlinear dynamic behavior and modeling of fluid-driven soft twisted tower mechanisms and establishes a foundation for their integration into compliant underwater robotic arms.