Research On Innovative Design And Adaptive Control Strategy Of An Underwater Bionic Soft Robot With Multiple Motion Modes

Underwater soft robots possess excellent flexibility,impact resistance,environmental adaptability,and biocompatibility,which are of great research significance and application potential in fields such as marine ecological environment monitoring and underwater biodiversity exploration.Underwater exploration tasks face challenges such as water flow disturbances and narrow and rugged underwater environments,requiring underwater soft robots to have multiple motion modes,efficient swimming capabilities,high-quality path navigation,and precise trajectory tracking control.However,the nonlinear characteristics of soft materials and the interference of unknown underwater environments make the already complex exploration process even more complicated and difficult to control.Therefore,the focus of this paper is on how to achieve efficient and precise completion of underwater exploration tasks by underwater soft robots in narrow and rugged underwater environments.The main contributions of this paper are as follows:A underwater bionic soft robot with multiple controllable transition modes is designed and the motion performance of walking on land and swimming on the water surface is verified.Based on the movement characteristics of the mantis shrimp,this study designed an underwater bionic soft robot using dielectric elastomer-driven materials.This robot not only has controllable cyclic motion modes,such as narrow space forward and backward movement,transition from walking on land to swimming on the water surface,transition from diving on the water surface to crawling on the underwater,and transition from crawling on the underwater to walking on land,but also has high speed,adaptability,and flexibility.This greatly enhances the feasibility and completion of exploration tasks in narrow and rugged underwater environments.To address the challenges of low propulsion efficiency and poor adaptability in the swimming process of underwater bionic soft robots,this study combines PIV experiments and fluid finite element simulation methods to optimize the design of underwater bionic soft robots under sudden excitation.The goal is to develop the geometric structure that achieves the best balance between motion efficiency and adaptability.Based on this,hydrodynamic models of underwater bionic soft robots with different structures,rotational speeds,and flexibility angles are constructed to accurately represent-the dynamic characteristics of different structures and flexibility angles under sudden excitation.To overcome the challenges of low path planning efficiency and high motion cost for underwater soft robots in narrow and rugged underwater environments,an adaptive RRT-Connect planning strategy is developed.This strategy incorporates an extended step size adjustment scheme,an obstacle environment detection model,and an optimized post-processing algorithm.It can rapidly and efficiently plan high-quality paths for traversing narrow and rugged underwater environments,thereby reducing the motion cost of underwater bionic soft robots in exploration tasksAiming at the large uncertainty in the trajectory tracking control process of underwater bionic soft robots in narrow and rugged underwater environments,an adaptive fractional-order nonsingular terminal sliding mode controller is developed.This controller incorporates a nonlinear disturbance observer,an adaptive algorithm,a saturation function approach,and a fractional-order nonsingular terminal sliding mode surface.By considering the nonlinear hysteresis,creep,and rate-dependent hysteresis behaviors in the dynamic model,the controller effectively enhances the capability to handle large parameter uncertainties and external disturbances,thereby improving the control accuracy and robustness of the underwater bionic soft robot control system in exploration tasksComprehensive experiments are conducted to validate the feasibility of the proposed adaptive strategies for underwater soft robots in executing underwater target exploration tasks.The experiments demonstrate that with the adaptive strategies proposed in this study,underwater soft robots can accurately complete underwater target detection tasks.