Pitch Motion Stabilizer Control for High-Frequency Marine Disturbances
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Solution Overview
Problem
Conventional pitch motion stabilizers in marine vessels are unable to effectively control high-frequency pitch motions due to dynamic response limitations, leading to inefficient pitch control.
Innovation Solution
A computer system that discriminates between low-frequency and high-frequency pitch motions, controlling the pitch motion stabilizer by adjusting the trim angle in response to high-frequency pitch accelerations using open-loop control, with features like gain factors, dead bands, and saturation levels to enhance responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If closed loop control is used for pitch motion stabilizer, then control precision is improved for low-frequency pitch motions, but control effectiveness deteriorates for high-frequency pitch motions due to dynamic response limitations
Solution Approach 1:
The system dynamically adapts its control strategy based on the frequency characteristics of pitch motions. For low-frequency pitch motions, closed-loop control is applied to achieve precise control. For high-frequency pitch motions, the system switches to open-loop control with trim angle reduction to overcome the dynamic response limitations of the stabilizer. This dynamic adaptation resolves the contradiction by matching the control method to the operational requirements at different frequency ranges.
Solution Approach 2:
The system changes the control parameters and strategy based on the frequency of pitch disturbances. By identifying the frequency range of pitch motions and adjusting the control approach accordingly (closed-loop for low-frequency, open-loop with trim reduction for high-frequency), the system optimizes control effectiveness across different operational conditions, resolving the contradiction between control precision and response speed.
2Productivity
If pitch motion stabilizer dynamics are increased to respond to high-frequency pitch motions, then control effectiveness for high-frequency pitch motions is improved, but system complexity and response time requirements increase
Solution Approach 1:
The control system segments the pitch motion frequency spectrum into low-frequency and high-frequency ranges. For low-frequency range, conventional closed-loop control is used. For high-frequency range, the system applies a different control approach (open-loop with trim angle reduction). This segmentation allows each control mode to be optimized for its specific frequency range without requiring the entire system to be redesigned for high-frequency performance, thus improving control effectiveness while managing system complexity.
Solution Approach 2:
Rather than increasing the physical dynamics of the pitch motion stabilizer to handle high-frequency motions, the system dynamically selects appropriate control strategies based on frequency detection. This approach achieves improved control effectiveness for high-frequency pitch motions without physically modifying the stabilizer's dynamic characteristics, thereby avoiding the associated increase in system complexity and response time requirements.
3Speed
If open-loop control with trim angle reduction is applied for high-frequency pitch motions, then control responsiveness is improved, but energy consumption and actuator workload increase
Solution Approach 1:
For high-frequency pitch motions, the system applies partial action by using open-loop control with trim angle reduction only when necessary (i.e., when high-frequency pitch disturbances are detected). The control effort is applied selectively rather than continuously, improving responsiveness when needed while minimizing unnecessary energy consumption during normal low-frequency operations where closed-loop control suffices.
Solution Approach 2:
The system dynamically determines when to switch between control modes based on the detected frequency characteristics of pitch motions. By activating the more energy-intensive open-loop control with trim reduction only during high-frequency disturbances and using the more energy-efficient closed-loop control for low-frequency motions, the system achieves improved responsiveness when required while optimizing overall energy consumption through adaptive mode selection.
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
The present disclosure relates to a computer system configured to actuate a pitch motion stabilizer of a marine vessel, the computer system comprising processing circuitry configured to obtain operating data indicative of a maximum frequency of operation of the pitch motion stabilizer, the maximum frequency of operation being indicative of a capability of the pitch motion stabilizer to suppress pitch disturbances acting on the marine vessel, setting a low-frequency pitch motion range and a high-frequency pitch motion range of the marine vessel, the low-frequency pitch motion range being a frequency range below the maximum frequency of operation of the pitch motion stabilizer, and the high-frequency pitch motion range being a frequency range above the maximum frequency of operation of the pitch motion stabilizer, obtain vessel motion data indicative of an amount of pitch accelerations by the marine vessel in the high-frequency pitch motion range, and reduce a trim angle of the marine vessel by controlling the pitch motion stabilizer in response to an increased amount of pitch accelerations by the marine vessel in the high-frequency pitch motion range.