Objective To address the inherent trade-off between large-scale exploration and high-precision manipulation in existing underwater vehicles, a novel morphable underwater intervention robot is developed. Designed for operations at depths up to 1000 m, the robot integrates low-drag cruising with dual-arm collaborative capabilities, satisfying the rigorous inspection and maintenance requirements of offshore wind farms and subsea oil and gas platforms.

Method Initially, the overall design specifications were defined, and the integrated design workflow was optimized. The configuration of the robot's pressure-resistant hulls and equipment layout were finalized, followed by the development of critical structures, including the morphing mechanism (lead screw lifting mechanism) and pressure-resistant hulls. Strength verification of key components was performed using Finite Element Analysis under a 12 MPa hydrostatic load, simulating a depth of 1000 m. Subsequently, the endurance and maneuverability during cruising mode, as well as the manipulator workspace and stability during manipulating mode, were systematically evaluated. Finally, hydrodynamic drag characteristics were verified through CFD simulations, and a coupled vehicle-manipulator dynamic model was established in Matlab to validate the robot’s self-recovery, disturbance rejection, and coupling suppression performance.

Results Results indicate that the internal layout is rational, with critical components meeting the operational requirements for 1000 m deep-sea environments; the maximum stress within the pressure hulls remains below the yield strength of the selected materials. In cruising mode, the robot achieves a maximum endurance of 7 h, and the configured propulsion system ensures high underwater maneuverability. At a cruise speed of 6 kn, the longitudinal drag is recorded at only 725.06 N, which is significantly lower than that in manipulating mode, demonstrating superior low-drag characteristics. In manipulating mode, the central buoyancy module is elevated by 270 mm, increasing the vertical distance between the center of gravity and the center of buoyancy by 0.054 m. Consequently, the maximum restoring moment increases by 202.1% compared to cruise mode, significantly enhancing operational stability. The heeling self-recovery time is shortened from 180 s to 60 s, alongside improved anti-disturbance capabilities. Furthermore, the dual-arm workspace effectively covers the lateral, forward, and downward regions of the vehicle, ensuring an efficient collaborative envelope.

Conclusion Through autonomous configuration switching, an overall design scheme for a morphable underwater intervention robot with multi-task execution capability was proposed, achieving the organic combination of low-resistance detection in cruising mode and high-stability operation in manipulating mode, thus providing an innovative solution for underwater operations in complex deep-sea scenarios.