Ship Motion Control Device Using Segmented PID Feedback
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Solution Overview
Problem
Existing motion control systems for ships with outboard engines require time-consuming weight adjustments in performance functions and are prone to control failures due to incomplete optimization calculations within a set prediction horizon.
Innovation Solution
A motion control device and method that integrates optimization calculation into feedback control, utilizing a classical control system like PID control, eliminating the need for weight adjustments and reducing the likelihood of control failures by distributing operation amounts for outboard engines based on predefined constraint conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If model predictive control is used to control propulsion forces, then motion control precision is improved, but the control system fails when optimization calculation is not completed within prediction time
Solution Approach 1:
The patent divides the control system into two independent parts: a trajectory generator that calculates optimal trajectories using model predictive control, and a controller that executes feedback control using classical PID algorithms. This segmentation allows the optimization calculation to be performed offline or in advance, while the real-time control relies on the reliable PID feedback mechanism, thus preventing control failures when optimization timing is exceeded.
Solution Approach 2:
The patent introduces a trajectory generator as an intermediary component that pre-calculates optimal trajectories based on desired motion and ship dynamics. This trajectory generator acts as a mediator between the high-level motion planning and the low-level control execution, ensuring that the control system has advance knowledge of optimal paths while relying on robust feedback control for real-time execution, thereby eliminating the risk of optimization timing failures.
2Measurement precision
If performance function weights are adjusted on trial-and-error basis, then optimal control performance is achieved, but adjustment time increases
Solution Approach 1:
The patent changes the approach to performance optimization by shifting from adjusting weight parameters on trial-and-error basis to using a systematic trajectory generation method. The trajectory generator uses mathematical models and constraint-based optimization to automatically determine optimal trajectories, eliminating the need for manual weight adjustment and significantly reducing the time required to achieve optimal control performance.
Data Source
AI summary
To provide a motion control device for a ship, which does not require adjustment of weights of an performance function, and is less liable to fail in control calculation by building optimization calculation only into a part of classical feedback control, the motion control device, which is configured to cause a ship, on which a plurality of outboard engines are installed, to cruise along a desired trajectory, includes: a trajectory generator configured to output a trajectory command; a controller configured to output a control force command based on the trajectory command and a sensor information group output from a sensor group provided for the ship; and a control force distributor configured to carry out, based on the control force command, optimization calculation for operation amounts required for the plurality of outboard engines in accordance with a constraint condition set in advance so as to output the operation amounts.