Adaptive Positioning Control for Towed Seismic Instrumented Cables
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Solution Overview
Problem
Existing systems for dynamic positioning of marine instrumented cables during seismic surveys are not robust enough to handle varying operational conditions and external disturbances, leading to inaccuracies and potential entanglement, which increases survey time and costs.
Innovation Solution
A method and system utilizing a model predictive adaptive controller (MPAC) that continuously updates power control output based on prediction errors to counteract un-modeled dynamics and insecurity in model parameters, ensuring stable and precise positioning of instrumented cables by integrating prediction error rather than control error.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional control systems are used for dynamic positioning of instrumented cables, then the system structure is relatively simple, but the positioning accuracy deteriorates under varying operational conditions and external disturbances
Solution Approach 1:
The patent implements a dynamic adaptive controller that continuously adjusts control parameters based on real-time prediction errors. The controller transitions from static to dynamic operation by updating control gains and parameters adaptively in response to changing operational conditions and external disturbances, thereby maintaining high positioning accuracy without requiring overly complex fixed-structure systems
Solution Approach 2:
The patent employs feedback mechanisms where prediction errors from the adaptive model are continuously fed back to adjust control parameters. This closed-loop feedback system uses the difference between predicted and actual cable positions to dynamically modify controller behavior, improving positioning accuracy while managing complexity through intelligent feedback processing
2Stability of the object's composition
If the vessel cruises for three instrumented cable lengths before survey begins, then the instrumented cable distribution approaches ideal arrangement, but the survey time increases
Solution Approach 1:
The patent applies preliminary action by using the adaptive controller to establish ideal cable arrangements before the survey actually begins. The system proactively adjusts cable positions during deployment and initial cruising phases, predicting and correcting deviations in advance, so that the cable array reaches optimal configuration much faster than conventional methods, reducing the required stabilization distance and survey time
3Reliability
If instrumented cables are towed in parallel, then survey coverage is improved, but the risk of cable entanglement increases
Solution Approach 1:
The patent applies local quality by implementing individualized adaptive control for each instrumented cable within the parallel array. Each cable receives tailored control adjustments based on its specific position, local environmental conditions, and interaction with adjacent cables. This localized control prevents uniform deviations that could lead to entanglement while maintaining the parallel configuration needed for comprehensive survey coverage
Solution Approach 2:
The adaptive controller acts as an intermediary between the towing vessel and the instrumented cables, mediating their interactions. It continuously monitors relative positions and predicts potential entanglement scenarios, then adjusts individual cable positions proactively to maintain safe separation distances, preventing harmful entanglement effects while preserving the benefits of parallel towing for survey coverage
Data Source
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AI summary
The invention is related to a method and system for dynamic positioning (DP) of marine instrumented cables. By means of a model predictive adaptive controller the power control output of a nominal controller is compensated and therethrough one achieve a more rapid and precise controlling of the control devices and accordingly the instrumented cables.