Real-Time Roll Angle Decomposition With Delay-Compensated Filtering
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Solution Overview
Problem
Conventional methods for estimating the heeling angle of a marine vessel face challenges in accurately decomposing vessel motion signals into non-overlapping frequency components in real-time, due to distortion and time delays introduced by filters, which compromise operational safety.
Innovation Solution
A computer-implemented method that decomposes a roll angle signal into frequency components by using a high pass filter with a specific cut-off frequency, reconstructing and adjusting the signal to minimize distortion and delay, and employing directional change and envelope detection to refine the heeling angle estimation, achieving precise signal separation with minimal delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional low pass filters (IIR or FIR) are used to isolate low frequency components, then frequency separation is achieved, but significant time delay and distortion are introduced
Solution Approach 1:
The patent segments the filtering process into multiple stages: a first filter provides coarse frequency separation, while a second filter with opposite characteristics compensates for the delay and distortion. This segmentation allows each filter to be simpler while the combination achieves both accurate frequency separation and minimal time delay.
Solution Approach 2:
The patent introduces an intermediary compensation filter that processes the output of the first filter. This intermediary element (the second filter) is specifically designed to counteract the adverse effects (delay and distortion) introduced by the first filter, thereby restoring the signal while maintaining frequency separation.
2Loss of time
If FIR low pass filters are used to reduce time delay, then delay is reduced to milliseconds, but attenuation of unwanted high frequency components becomes very poor
Solution Approach 1:
The patent merges the strengths of two different filter types by combining them in sequence. The first filter (can be IIR) provides strong attenuation of unwanted frequencies, while the second compensatory filter (can be FIR with linear phase) corrects the delay and distortion. The combination achieves both good attenuation and minimal delay.
Solution Approach 2:
The patent changes the parameters of the filtering system by using two filters with complementary characteristics rather than one filter. The first filter is optimized for attenuation, while the second is optimized for phase linearity and delay compensation. This parameter optimization across multiple components resolves the contradiction.
3Loss of time
If IIR low pass filters are used with relaxed attenuation, then time delay is reduced to more than 2 seconds, but sufficient attenuation of unwanted components cannot be achieved
Solution Approach 1:
The patent segments the filtering function between two separate filters. The first IIR filter provides the necessary attenuation with moderate delay, while the second compensatory filter addresses the remaining delay and distortion issues. This segmentation allows achieving both attenuation and acceptable delay.
Solution Approach 2:
The second compensatory filter acts as an intermediary that processes the output of the first IIR filter. It compensates for the delay and distortion introduced by the first filter, thereby enabling the first filter to be designed with relaxed attenuation requirements while still achieving the overall system goals.
Data Source
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AI summary
The invention is a method that combines the following components: 1. a high pass filter designed to have sufficiently small phase delay and roll-off value in transition band as well as sufficiently good attenuation; 2. a distortion detection and reconstruction introduced by the application of the high pass filter by extraction the significant frequency components in relevant frequency band; 3. 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); 4. 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 5. a time-domain correction method during and immediately after sudden changes in composite signal (spike) is detected.