Jack-up Vessel Environmental Force Estimation
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Solution Overview
Problem
Dynamic positioning systems struggle to accurately estimate environmental forces acting on jack-up vessels when they transition from being supported by legs to floating in water, leading to positional excursions due to unknown environmental forces.
Innovation Solution
A method involving positioning the vessel in a force determination position, measuring strain on support legs with thrust variations to calculate accurate environmental forces, accounting for scaling and offset errors using algorithms like regression or polynomial relationships.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the vessel is raised out of the water and supported on the sea-bed by support legs, then the vessel forms secure platforms for operations, but it becomes impossible for the dynamic positioning system to estimate environmental forces in a conventional manner
Solution Approach 1:
The system performs preliminary calibration actions while the vessel is in the supported state by measuring strain on the support legs under known thrust conditions. This preliminary data collection enables the DP system to estimate environmental forces during the transition and when unsupported, resolving the measurement impossibility contradiction.
Solution Approach 2:
Strain measurements on the support legs serve as an intermediary indicator to infer environmental forces. Instead of directly measuring environmental forces when unsupported, the system uses strain data from the supported state as a mediator to calculate the forces acting on the vessel.
2Productivity
If previous measurements of environmental forces are used when the vessel transitions from supported to unsupported, then the system maintains continuity, but positional excursions occur due to changed environmental conditions
Solution Approach 1:
The system uses real-time strain measurements from support legs as feedback during the transition process. This feedback enables continuous updating of environmental force estimates, allowing the DP system to adjust thrust commands dynamically and maintain position control accuracy throughout the transition.
Solution Approach 2:
The system transitions from using static previous measurements to dynamic real-time strain-based estimation. By continuously monitoring strain variations during the transition and updating force estimates accordingly, the system adapts to changing environmental conditions while maintaining position control.
3Measurement precision
If strain measurements on support legs are used to estimate environmental forces, then accurate force estimation is achieved when supported, but the system cannot directly measure forces when the vessel is unsupported
Solution Approach 1:
The strain measurement system on the support legs is designed to serve multiple functions: directly measuring forces when the vessel is supported, and providing calibration data for estimating forces when the vessel is unsupported. This multi-functionality resolves the contradiction between measurement precision in the supported state and adaptability to unsupported operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides precise estimates of environmental forces, reducing positional excursions and enabling controlled transitions from supported to unsupported states by the legs, maintaining vessel stability.
Implementation Method 1
measuring the strain on at least one support leg of the jack-up vessel
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention provides a method of estimating the environmental force acting on a supported jack-up vessel (1). The vessel (1) is positioned in a force determination position and the strain on at least one support leg (3) of the jack-up vessel (1) is measured while a first thrust is applied to the vessel (1). A second thrust is applied to the vessel (1) whilst the vessel (1) is maintained in the force determination position. The variation in the strain in the at least one support leg (3) is monitored as the second thrust is applied and the strain is used to calculate an estimate of the environmental force acting on the vessel (1). The method allows a dynamic positioning (DP) system of the jack-up vessel (1) to determine a suitable thrust to apply to the vessel (1) as the support legs (3) of the vessel (1) are raised. By applying this suitable thrust the position of the vessel (1) can be maintained when the vessel (1) transitions from being supported by the support legs (3) to being supported by water (2).