Sliding mode anti-saturation control of a depth-varying maneuver of supercavitating vehicle

This study addresses the challenges of depth-varying maneuver control and attitude stabilization for supercavitating vehicle under lumped uncertainties and input saturation constraints. A composite control strategy integrating a finite-time extended state observer with an anti-saturation compensator is proposed, which innovatively combines super-twisting algorithm and fixed-time convergent sliding mode control technology to enhance system robustness and suppress control chattering. First, the finite-time extended state observer is designed to achieve finite-time estimation the lumped uncertainties. Secondly, the anti-saturation compensator is employed to dynamically regulate control inputs, effectively eliminating nonlinear effects caused by actuator saturation. Finally, a fixed-time convergent sliding mode is designed using a hyperbolic-tangent-like function, which is synergistically integrated with the super-twisting algorithm to formulate a super-twisting controller. This methodology ensures accurate convergence of tracking errors while significantly attenuating chattering phenomena inherent in traditional sliding mode control. Lyapunov stability analysis proves the global finite-time stability of the closed-loop system. The effectiveness of finite-time extended state observer and anti-saturation compensator are verified by simulation, and the combined control method proposed in this paper has better performance compared with other methods.