Gangway Control System with Local Camera Feedback
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Solution Overview
Problem
Existing gangway control systems face challenges in achieving accurate positioning and stability during the landing process due to non-minimum phase problems caused by flexible gangway structures, which can lead to oscillations and potential damage.
Innovation Solution
The solution involves introducing a second sensor with non-optimal placement to increase accuracy, and processing the secondary measurement signal to separate non-minimum phase frequency content, using a bias value to correct the global position measurement, thereby avoiding instability issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a local position measurement unit (camera) is positioned at the distal end of the gangway to improve positioning accuracy, then measurement precision is improved, but the system becomes non-minimum phase and unstable due to flexible structure dynamics
Solution Approach 1:
The patent introduces an intermediary coordinate transformation mechanism that mediates between the local camera measurement at the distal end and the global positioning system at the base. By transforming camera measurements into base coordinate system and combining with GPS/MRU data, the system achieves accurate positioning without directly feeding distal end measurements into the control loop, thus avoiding excitation of flexible mode oscillations while maintaining measurement precision
Solution Approach 2:
The patent replaces direct mechanical feedback from the distal end (which causes non-minimum phase instability) with an optical measurement system (camera) combined with computational coordinate transformation. This substitution allows accurate measurement of distal end position while using base-frame control signals that avoid exciting flexible structure dynamics
2Productivity
If feedback loop gain is increased to improve control performance and compensate for disturbances, then control effectiveness is improved, but oscillation risk increases due to non-minimum phase characteristics
Solution Approach 1:
The patent implements a dual feedback architecture: (1) Global feedback from GPS and MRU measurements at the base provides stable, low-frequency position correction; (2) Local feedback from the camera provides high-frequency position refinement. By separating these feedback paths and processing them through coordinate transformations, the system maintains high control performance while filtering out oscillatory components that would result from direct distal end feedback
Data Source
AI summary
The present invention relates to a control system and a corresponding method suitable for controlling a gangway structure gangway, crane or similar suitable for transferring personnel or goods to or from a floating structure such as a sea vessel relative to a fixed or moving landing point. The system including global position measurement of the position of the floating structure and the position of the landing point, and thus a first relative position between the floating structure and the landing point, and a control unit configured to move the gangway relative to the landing point. The system also includes a local position measurement unit positioned at or in relation to the distal end of the gangway being configured to measure a second relative position between the landing point and the gangway distal end, the local position measurement unit being connected to the control system unit so as to communicate the second relative position to the control system unit. The system is configured to adjust the first relative position based on the second relative position resulting in a corrected reference signal, the control unit being configured to adjust the position of the gangway so as to position the gangway distal end to the desired position relative to the landing point.