Active Noise Control Using Feedforward-Feedback FIR Architecture
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Solution Overview
Problem
Existing active noise cancellation systems struggle to effectively address both periodic and non-periodic disturbances, often resulting in over-amplification of non-periodic components due to the marginal instability of standard memory loops and the need for high-order internal models designed on a trial-and-error basis.
Innovation Solution
The implementation of a broadband feedforward sound compensation system using a generalized Finite Impulse Response (FIR) filter that accounts for the dynamic effects of sound propagation, combined with a feedback system that designs a low-order controller to separately attenuate periodic disturbances without amplifying non-periodic components, utilizing adaptive and recursive estimation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard memory loop is used for periodic disturbance rejection, then periodic noise cancellation is improved, but the system becomes marginally unstable and requires high-order internal models designed on a trial-and-error basis
Solution Approach 1:
The patent transforms the controller design from trial-and-error parameter tuning to a systematic approach by changing the mathematical parameters used in controller synthesis. It employs H2 optimal control theory with structured uncertainty to derive controller parameters analytically, eliminating the need for high-order internal models and trial-and-error design while maintaining periodic disturbance rejection capability.
Solution Approach 2:
The patent replaces the mechanical trial-and-error design process with a mathematical optimization framework. By substituting the iterative mechanical tuning approach with H2 optimal control theory and structured singular value analysis, the system achieves stable periodic noise cancellation with lower-order controllers through analytical parameter optimization rather than empirical trial-and-error.
2Reliability
If a feedback controller is designed to reject periodic disturbances, then periodic noise is attenuated, but non-periodic components are over-amplified
Solution Approach 1:
The patent segments the disturbance spectrum into periodic and non-periodic components and designs separate control strategies for each. The feedback controller is specifically tuned to reject periodic disturbances through H2 optimal control with structured uncertainty, while the feedforward controller handles non-periodic components, preventing their over-amplification by addressing each disturbance type with its dedicated control mechanism.
Solution Approach 2:
The patent introduces a feedforward controller as an intermediary element that works in conjunction with the feedback controller. This feedforward component serves as a mediator that specifically addresses non-periodic disturbances before they can be amplified by the feedback loop, while the feedback controller focuses exclusively on periodic disturbance rejection, creating a coordinated two-layer control architecture.
3Reliability
If passive noise cancellation using sound absorbing materials is used, then noise reduction is achieved, but the system becomes bulky and less efficient
Solution Approach 1:
The patent replaces the passive mechanical noise cancellation approach using sound-absorbing materials with an active electronic control system. By substituting bulky physical absorption materials with electronic sensors, processors, and actuators that generate anti-noise signals, the system achieves equivalent or superior noise reduction with significantly reduced physical bulk and improved efficiency.
Solution Approach 2:
The patent employs periodic action by generating anti-noise signals that are precisely timed and phased to destructively interfere with the original noise waves. This active periodic counter-action replaces the static passive absorption approach, allowing dynamic noise cancellation that adapts to changing noise conditions while maintaining a compact system architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient and precise noise cancellation, reducing noise levels without over-amplifying non-periodic components, and is applicable to a wide range of devices and systems, including forced air and electronic systems.
Implementation Method 1
a sound disturbance is measured at an upstream location of the (noisy) sound propagation and cancelled at a downstream direction of the (noisy) sound propagation
Implementation Method 2
generating an out-of-phase sound source
Implementation Method 3
The inventive active noise control algorithm described in this invention uses a FIR (Finite Impulse Response) filter where the orthogonal basis functions in the filter are chosen on the basis of the dynamics of the sound propagation
Implementation Method 4
active noise control using a feedforward or a feedback controller
Data Source
AI summary
An active noise control apparatus for reducing noise from a noise source includes a microphone for detecting noise produced by the noise source, and a generalized finite impulse response (FIR) filter for receiving noise signals of the detected noise from the microphone and generating control signals for reducing the noise from the noise source. A speaker produces sound based on the control signals from the generalized FIR filter for substantially canceling the noise from the noise source.