Marine Vessel Station Keeping With Pulsed Thrust Control

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Solution Overview

Problem

Existing marine vessel positioning systems often overshoot target positions when transitioning from active to inactive modes, particularly with stern drives or outboard motors, due to large thrust increments, leading to inefficiencies and potential loss of control.

Innovation Solution

A control module algorithm that utilizes an input-output map to control the timing and frequency of thrust production by marine propulsion devices, including disengagement of propellers to allow vessels to coast, thereby minimizing position and heading errors without overshooting, and an adaptive gain strategy to limit thrust discontinuities, ensuring precise station keeping.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If large thrust increments are used to maintain position, then response speed improves, but position precision deteriorates due to overshooting

Engineering Contradiction:

Improveresponse speedVSAvoidposition precision

Core Design Contradiction:

SpeedVSManufacturing precision

Solution Approach 1:

The system dynamically adjusts thrust magnitude based on real-time position error and velocity feedback. When the vessel is far from target, larger thrust increments are applied for faster response. As the vessel approaches the target, thrust magnitude is automatically reduced to prevent overshooting, thereby maintaining both response speed and position precision.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The control system continuously monitors vessel position, velocity, and thrust application, using this feedback to adjust subsequent thrust commands. This closed-loop control ensures that large thrust increments produce rapid response while the system compensates for momentum and prevents overshooting by reducing thrust as the target position is approached.

Inventive Principle:

Principle #23Feedback

2Stability of the object's composition

If continuous thrust production is used to maintain position, then position stability improves, but energy consumption increases

Engineering Contradiction:

Improveposition stabilityVSAvoidenergy consumption

Core Design Contradiction:

Stability of the object's compositionVSUse of energy by moving object

Solution Approach 1:

Instead of continuous thrust, the system applies periodic thrust pulses synchronized with the vessel's oscillation period. This allows the vessel to coast during non-thrust periods, significantly reducing energy consumption while maintaining position stability through strategically timed thrust applications that counteract drift and oscillations.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The system maintains continuous position control not through continuous thrust, but through continuous monitoring and periodic correction. The control algorithm continuously calculates optimal thrust timing and magnitude, ensuring that thrust is applied only when and where it produces useful corrective action, thereby minimizing energy waste while maintaining stability.

Inventive Principle:

Principle #20Continuity of useful action

3Manufacturing precision

If frequent thrust discontinuities are applied to minimize position error, then position precision improves, but mechanical wear increases

Engineering Contradiction:

Improveposition precisionVSAvoidmechanical lifespan

Core Design Contradiction:

Manufacturing precisionVSDuration of action of stationary object

Solution Approach 1:

The system changes operational parameters by smoothing thrust transitions and limiting the frequency of thrust discontinuities. Instead of making frequent small adjustments that cause mechanical wear, the algorithm optimizes for fewer, more deliberate thrust changes that achieve position correction while reducing stress on power transmission components.

Inventive Principle:

Principle #35Parameter changes

4Reliability

If high thrust magnitude is used to counteract strong currents, then position maintaining capability improves, but noise and vibration increase

Engineering Contradiction:

Improveposition maintaining capabilityVSAvoidnoise and vibration

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The control system applies preliminary counter-thrust before the vessel is significantly displaced by strong currents. By anticipating and counteracting current effects early, the system maintains position with smaller, less disruptive thrust magnitudes rather than requiring large corrective thrusts that generate excessive noise and vibration.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS11327494B1Station keeping methods

Publication Date: 2022.05.10 BRUNSWICK CORP

AI summary

A method for maintaining a marine vessel propelled by a marine propulsion device in a selected position includes determining a current global position of the marine vessel and receiving a signal command to maintain the current global position. The current global position is stored as a target global position in response to receiving the signal command. A subsequent global position of the marine vessel is determined and a position error difference between the subsequent global position and the target global position is determined. The method includes determining marine vessel movements required to minimize the position error difference, and causing the marine propulsion device to produce a thrust having a magnitude, a direction, and an angle calculated to result in achievement of the required marine vessel movements. At least one of timing and frequency of discontinuity of thrust production is controlled while the position error difference is minimized.