How do you handle thruster faults and failures in your thruster allocation algorithm?

1 Fault detection and isolation

The first step in handling thruster faults and failures is to detect and isolate them as soon as possible. This can be done by using various sensors and monitors, such as current, voltage, temperature, vibration, and pressure, to measure the health and status of each thruster. If a fault or failure is detected, the thruster should be isolated from the DP system and the operator should be alerted. Fault detection and isolation can also be automated by using fault-tolerant control techniques, such as observer-based methods, adaptive methods, or sliding mode methods.

2 Fault accommodation and reconfiguration

The second step in handling thruster faults and failures is to accommodate and reconfigure the DP system to cope with the reduced or changed thruster capacity. To do this, different thruster allocation methods and algorithms are used to distribute the required forces and moments among the available thrusters. These include quadratic programming, which minimizes a quadratic cost function subject to linear or nonlinear constraints; genetic algorithm, which uses a population-based search technique to find an optimal or near-optimal solution for the thruster allocation problem; and fuzzy logic, which uses a set of linguistic rules based on expert knowledge to assign the thruster forces and moments, taking into account the uncertainty and imprecision of the DP system.

3 Fault recovery and restoration

The third step in handling thruster faults and failures is to recover and restore the faulty or failed thruster, if possible, or replace it with a spare or alternative one. This can be done by using various maintenance and repair strategies, such as preventive, corrective, or predictive maintenance, depending on the type and severity of the fault or failure. The recovery and restoration process should also consider the operational and environmental conditions, such as weather, sea state, or mission requirements, to ensure the safety and efficiency of the DP system.

4 Fault prevention and mitigation

To prevent and mitigate thruster faults and failures as much as possible, various design and operational measures should be taken. This includes using robust and reliable components and materials, such as motors, gears, bearings, seals, and propellers that can withstand harsh conditions and loads. It is also important to have redundant and diverse thruster configurations, like azimuthing, tunnel, or retractable thrusters that can provide backup or alternative options in case of failure. Furthermore, regular and thorough inspection and testing of the thrusters and their associated systems should be conducted to detect and correct any anomalies or defects. Lastly, adequate and appropriate training and education of the DP operators and crew should be done to enhance their awareness and skills in handling thruster faults and failures.

5 Fault analysis and evaluation

The fifth step in handling thruster faults and failures is to analyze and evaluate them, using data logging and recording, fault diagnosis and identification, fault simulation and modeling, and fault reporting and feedback. Data logging involves collecting and storing data related to the thruster faults and failures, such as time, location, type, cause, effect, and response. Fault diagnosis involves analyzing the data to determine the root cause of the fault or failure. Fault simulation uses mathematical models to simulate the fault or failure scenarios. Finally, fault reporting communicates the results of the evaluation with relevant stakeholders for quality assurance.

6 Fault learning and improvement

The sixth step in handling thruster faults and failures is to learn from them and improve the thruster allocation algorithm and the DP system accordingly. This can be done through fault adaptation and optimization, which involves updating and modifying the thruster allocation algorithm to adapt to the changing or reduced thruster capacity, as well as optimizing the DP system performance and efficiency. Fault correction and compensation is another approach, which involves correcting and compensating for the fault or failure effects on the DP system output and behavior. Finally, fault prevention and avoidance involves preventing and avoiding future thruster faults and failures, by using techniques such as fault prediction, fault prognosis, or fault management.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?