Ship Autopilot Parameter Scaling for Speed-Independent Steering
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Solution Overview
Problem
Existing automatic steering systems for ships face deterioration in control performance when ship speed changes, leading to inadequate steering control.
Innovation Solution
An automatic steering device that utilizes processing circuitry to acquire ship length and speed, identify non-dimensionalizing motion parameters, and generate dimensionalizing motion parameters to set control parameters for the model-based controller, allowing for adaptive control regardless of ship speed changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the control parameter is fixed for automatic steering, then the device complexity is reduced, but the control performance deteriorates when ship speed changes
Solution Approach 1:
The control parameter is made dynamic by introducing speed-dependent scaling factors. The dimensionalizing motion parameter is calculated based on the current ship speed, allowing the control parameter to adapt automatically to speed changes without requiring complex manual adjustment mechanisms
Solution Approach 2:
The invention changes the control parameter based on ship speed by introducing a dimensionalizing motion parameter that scales the non-dimensionalizing motion parameter according to speed. This allows the control system to maintain optimal performance across different operating conditions while using a relatively simple parameter adjustment mechanism
2Adaptability or versatility
If the control parameter is updated frequently in response to ship speed changes, then the adaptability is improved, but the loss of time for parameter calculation increases
Solution Approach 1:
The control parameter is updated periodically based on speed threshold changes rather than continuously. When the ship speed changes by more than a predetermined threshold, the processing circuitry calculates the dimensionalizing motion parameter and updates the control parameter, balancing adaptability with computational efficiency
3Measurement precision
If the non-dimensionalizing motion parameter is identified using motion information from the current control mode, then the measurement precision is improved, but the reliability decreases when control mode switching occurs
Solution Approach 1:
The processing circuitry stores the non-dimensionalizing motion parameter identified from the previous control mode before switching occurs. When control mode switching happens, the stored parameter from the prior mode is used, ensuring continuous and reliable control parameter identification without gaps or inaccuracies during the transition
Data Source
AI summary
To control an automatic steering appropriately regardless of a ship speed, an automatic steering device includes processing circuitry. The processing circuitry acquires motion information including a ship length and a ship speed. The processing circuitry identifies a non-dimensionalizing motion parameter based on the ship length and the motion information. The processing circuitry generates a dimensionalizing motion parameter by dimensionalizing the non-dimensionalizing motion parameter based on the ship speed. The processing circuitry sets a control parameter of the model-based controller based on the dimensionalizing motion parameter.