Zero Crossing Detection for Indirect TPMS Using Digital Signal Processing
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Solution Overview
Problem
Traditional tire pressure monitoring systems (TPMS) using analog comparators for magnetic field sensors suffer from high noise floors, which obscure vibration information needed for indirect tire pressure measurement, making it difficult to accurately determine zero crossing times and generate low noise speed signals.
Innovation Solution
A digital signal processor is used to estimate zero crossing events by fitting polynomials to sensor signal samples, allowing for the generation of low noise speed signals and preserving accurate zero crossing instants, thereby enabling the identification and analysis of vibration information for use in indirect TPMS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional analog comparators are used for magnetic field sensing, then the system structure is simple, but the noise floor is high which obscures vibration information
Solution Approach 1:
The patent replaces traditional analog comparator-based magnetic field sensing with a digital component that samples the magnetic field signal and uses polynomial fitting to detect zero crossings. This substitution of digital signal processing for analog circuitry reduces the noise floor while maintaining the essential sensing function, directly resolving the contradiction between simple structure and low noise performance.
Solution Approach 2:
The patent introduces polynomial fitting as an intermediary processing step between magnetic field sampling and zero crossing detection. By fitting polynomials to sampled data points, the system can accurately determine zero crossing instants while filtering out high-frequency noise, thus reducing the noise floor without requiring complex hardware modifications.
2Measurement precision
If polynomial fitting is used to estimate zero crossing events, then the noise floor is reduced and vibration information is preserved, but the processing complexity increases
Solution Approach 1:
The patent applies polynomial fitting selectively to identify zero crossing events rather than processing the entire magnetic field signal continuously. By focusing computational resources only on regions where zero crossings are detected, the system achieves high measurement precision while limiting the increase in processing complexity to only the necessary portions of signal analysis.
Solution Approach 2:
The patent performs preliminary sampling of the magnetic field signal at defined intervals before applying polynomial fitting. This preliminary action of collecting discrete data points prepares the signal for accurate zero crossing estimation without requiring continuous high-rate processing, thereby reducing overall processing complexity while maintaining detection accuracy.
3Loss of information
If digital sampling is used instead of analog comparison, then vibration information is preserved, but the signal processing requirements increase
Solution Approach 1:
The patent replaces analog comparison methods with digital sampling and polynomial-based zero crossing detection. This substitution preserves vibration information by maintaining the full signal waveform in digital form rather than reducing it to simple comparator outputs, while the polynomial fitting provides a systematic method for extracting zero crossing events from the digital data.
Data Source
AI summary
A magnetic speed sensor may comprise a digital component configured to estimate a zero crossing event based on a plurality of sensor signal samples. The digital component may output, to a control unit, a speed signal that is based on the estimated zero crossing event.