Real-Time Signal Decomposition for Low-Delay Heeling Angle Extraction

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Solution Overview

Problem

Conventional methods for decomposing vessel motion signals into frequency components suffer from significant time delays and distortion, making real-time stability assessments challenging, especially in offshore marine vessels where accurate separation of heeling angle components is crucial for safety.

Innovation Solution

A method involving a high pass filter with a cut-off frequency designed to separate low-frequency components from higher frequency components, followed by signal reconstruction and adjustment processes to compensate for phase delay and distortion, allowing for precise extraction of heeling angle components with minimal delay and distortion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If IIR low pass filter is used to extract low frequency components, then the filter provides sufficient attenuation of unwanted high frequency components, but the output delay becomes too large (more than 2 seconds) to satisfy real-time requirements

Engineering Contradiction:

Improveattenuation of unwanted componentsVSAvoidoutput delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Instead of using a low pass filter to extract low frequency components directly, the patent inverts the approach by using a high pass filter to extract high frequency components, then subtracting these from the original signal to obtain the low frequency components. This inversion allows real-time processing with minimal delay while achieving the desired frequency separation.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent introduces an intermediary high pass filter as a mediator to indirectly obtain the low frequency components. Rather than filtering low frequencies directly, the system filters high frequencies first, then uses signal subtraction to reveal the low frequency content, effectively using the high pass filter as an intermediary step.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Loss of time

If FIR low pass filter is used to reduce output delay to milliseconds range, then real-time requirements are satisfied, but the attenuation of unwanted high frequency components becomes very poor

Engineering Contradiction:

Improveoutput delayVSAvoidattenuation of unwanted components

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The patent applies the inversion principle by switching from low pass filtering to high pass filtering followed by signal subtraction. This allows the use of filters with minimal delay while achieving effective frequency separation through the mathematical operation of subtracting the high frequency component from the original signal.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent replaces the traditional mechanical filtering approach (using a low pass filter to directly extract low frequencies) with a signal processing substitution method. Instead of relying solely on filter characteristics, the system uses the combination of high pass filtering and signal subtraction to achieve the desired frequency separation with improved temporal response.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Loss of time

If high pass filter is used to separate low frequency components, then real-time processing is enabled with minimal delay, but the output contains phase delay and amplitude distortion of the remaining components

Engineering Contradiction:

Improveoutput delayVSAvoidphase delay and amplitude distortion

Core Design Contradiction:

Loss of timeVSMeasurement precision

Solution Approach 1:

The patent employs feedback by using the known characteristics of the high pass filter (phase delay and amplitude distortion) to correct the output signal. By characterizing the filter's effect and applying appropriate compensation, the system retrieves accurate low frequency components despite the initial distortion introduced by the high pass filter.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies parameter changes by adjusting the signal parameters (phase and amplitude) to compensate for the distortion introduced by the high pass filter. By modifying these parameters in the opposite direction of the distortion, the system recovers the original low frequency components with improved precision.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9923551B2Method of performing real time decomposition of a signal into components

Publication Date: 2018.03.20 ROLLS ROYCE PLC

AI summary

The invention is a method that combines the following components: a high pass filter designed to have sufficiently small phase delay and roll-off value in transition band as well as sufficiently good attenuation; a distortion detection and reconstruction introduced by the application of the high pass filter by extraction the significant frequency components in relevant frequency band; a signal compensation that reshapes the output of the high pass filter by matching the filter's phase delay and attenuation characteristics so as to approximate low frequency component extraction that would be produced by an ideal filter (very sharp frequency transition and no delay); a time-domain detection and correction method that addresses special circumstances under which the compensation would be inaccurate to achieve real-time estimate in normal circumstances, and a time-domain correction method during and immediately after sudden changes in composite signal (spike) is detected.