Abstract
A fault-tolerant supervisory control method for dynamic positioning of ships with actuator failures and sensor failures is presented in this paper. Unlike the traditional fault detection and control, fault detection and fault-tolerant controller are designed as a unit in this paper through a supervisor. By introducing a nonlinear estimation error and virtual controller, the sensor failures are separated from the actuator failures in the supervisory control system. It guarantees that the detectability property and matching property of the switched system are satisfied. Firstly, a new extended state observer is designed to match the models of different actuator failures. Secondly, by introducing a virtual controller, the detectability property of the switched system is guaranteed. Finally, a nonlinear estimation error operator is used in the designing of switching logic to guarantee stability of the closed-loop system with sensor failures. When sensor failures and actuator failures occur, we show that all the states of the closed-loop system are guaranteed to be bounded. The effectiveness of the fault-tolerant control is verified by simulation experiments.
Highlights
It is well known that failures can lead to a significant degradation in the performance of plant and may even make the system unstable
By augmenting a new state and utilizing acceleration feedback technology, the extended state observer proposed in this paper based on (3) will improve disturbance attenuation performance compared to the traditional one [9, 35]
When a sensor failure occurs at 250s, there is a slight fluctuation in the transition progress, the signal σ can switch to the stable controller, and positions of the vessel are stabilized near the equilibrium point eventually
Summary
It is well known that failures can lead to a significant degradation in the performance of plant and may even make the system unstable. Fault detection and diagnosis mechanism, based on two techniques: the parity space approach and the Luenberger observer, was proposed to guarantee a fault-tolerant robust control for the dynamic positioning of an overactuated offshore supply vessel [12]. Most of FTC methods for DPS are based on the low-frequency model of the ship and generally assume that the upper bound of external disturbances is known, which is often difficult. Motivated by the above considerations, a fault-tolerant supervisory control method for dynamic positioning of ships with actuator failures and sensor failures is presented in this paper. (1) Unlike in [11, 13, 15] where FTC methods for DPS are only based on the low-frequency model of the vessel which limits the range of applicability.
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