Adaptive Quantized Fault-Tolerant Control for a Riser-Vessel System With Unknown Control Direction and Input Saturation

With the burgeoning growth of the maritime economy, marine risers have emerged as reliable and convenient conduits for the transport of oil and natural gas. However, these risers are vulnerable to vibrational disturbances, which can adversely impact system performance and induce fatigue damage. Therefore, effective vibration control strategies are required to address this issue. This study introduces an innovative adaptive quantized fault-tolerant control strategy designed to attenuate vibrations in a three-dimensional (3-D) riser-vessel system against the effects of actuator faults, unknown control direction, and external disturbances. Different from previous findings, the suggested controller can directly counteract the nonlinear component stemming from actuator faults and handle the nonlinear decomposition inherent to the quantizer, without the necessity for upper-limit estimation. Furthermore, to tackle the input saturation, control laws are formulated using the hyperbolic tangent operator. Finally, the proposed controller's effectiveness and robustness are validated through thorough Lyapunov analysis and numerical simulations, affirming the system's uniformly bounded stability.