Continuous Moving Average Filter for Engine Signal Stability
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Solution Overview
Problem
Modern combustion engine control systems experience low-frequency oscillations due to signal aliasing when converting angular synchronous signals to time synchronous signals, leading to vibrations that discomfort vehicle occupants, and these oscillations are exacerbated by variations in engine components within manufacturing tolerances.
Innovation Solution
The implementation of a continuous moving average (CMA) anti-aliasing filter module that integrates and samples the angular synchronous signal, forming average values from the current and previous samples to create a time continuous time synchronous signal, which is then used to generate control signals for engine operations, thereby reducing signal aliasing and improving system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a predetermined sampling rate independent of engine velocity is used, then the control system operates with fixed timing, but signal aliasing occurs causing low-frequency oscillations
Solution Approach 1:
The patent applies dynamics by making the sampling rate variable rather than fixed. The sampling rate is dynamically adjusted based on the engine velocity signal, allowing the system to adapt to changing operating conditions. This resolves the contradiction by enabling the system to maintain accurate signal representation across varying speeds while avoiding aliasing oscillations that occur with fixed timing.
Solution Approach 2:
The patent changes the parameter of sampling rate from a constant value to a variable value that depends on engine velocity. By modifying this key parameter dynamically, the system achieves both reliable signal representation and adaptation to different operating conditions, eliminating the aliasing problem that arises with fixed sampling rates.
2Productivity
If angular synchronous signal is converted to time synchronous signal with predetermined sampling rate, then control signals can be generated, but low-frequency oscillations (3-7 Hz) occur due to signal aliasing
Solution Approach 1:
The patent implements dynamics by making the sampling rate variable based on engine velocity. This dynamic adjustment prevents signal aliasing that causes low-frequency oscillations while still enabling control signal generation. The system adapts its sampling characteristics to match the instantaneous engine speed, eliminating harmful oscillations.
Solution Approach 2:
The patent applies preliminary anti-action by preemptively adjusting the sampling rate to prevent aliasing oscillations before they occur. By dynamically synchronizing the sampling rate with engine velocity, the system prevents the generation of harmful low-frequency oscillations rather than attempting to correct them after they appear.
3Measurement precision
If dynamic triggering based on rotating element position is used, then accurate engine velocity measurement is achieved, but the time between pulses varies causing sampling inconsistencies
Solution Approach 1:
The patent resolves this contradiction by dynamically adjusting the sampling rate to match the instantaneous engine velocity. This maintains the benefits of dynamic triggering for accurate velocity measurement while compensating for varying pulse intervals through adaptive sampling, thereby achieving both measurement precision and sampling consistency.
Solution Approach 2:
The patent uses feedback by continuously monitoring engine velocity and using this information to adjust the sampling rate. This closed-loop approach ensures that the sampling process adapts to varying pulse intervals while maintaining consistent sampling timing, resolving the contradiction between measurement accuracy and sampling stability.
Data Source
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Figure 4A
AI summary
The present invention relates to a control system for an internal combustion engine comprising: a sensor configured to measure a rotational velocity of a rotating element connected to said engine and to provide an angular synchronous analog signal representing the rotational velocity; an analog-to-digital-converter (ADC) connected to the sensor to receive and convert the angular synchronous analog signal into a time continuous angular synchronous digital signal; a filtering module configured to receive and filter the digital signal using a continuous moving average anti aliasing filter to form a filtered time continuous time synchronous digital signal; and a control unit configured to form at least one time synchronous control signal based on the filtered digital signal, wherein the control signal is provided to an engine control system for controlling a performance parameter of said engine. The present invention also relates to a method for controlling an engine.