A Design of an Engine Speed Measurement System Based on Cigarette Lighter Signal Analysis in Vehicles

A Design of an Engine Speed Measurement System Based on Cigarette Lighter Signal Analysis in Vehicles

This study proposes a non-contact engine speed measurement system using vehicle electrical characterization to address the limitations of traditional contact-type methods and optical methods. The developed system collects coupled AC signals through a cigarette lighter interface and extracts the AC f...

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Bibliographic Details
Main Authors: Xuelian Li, Xuanze Wang, Jinping Yin, Da Liu, Zhongsheng Zhai
Format: Article
Language:English
Published: MDPI AG 2025-05-01
Series:Applied Sciences
Subjects:
engine rotation speed
spectral analysis
phase-difference compensation algorithm
sinusoidal least-squares fitting
Online Access:https://www.mdpi.com/2076-3417/15/10/5387
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Summary:This study proposes a non-contact engine speed measurement system using vehicle electrical characterization to address the limitations of traditional contact-type methods and optical methods. The developed system collects coupled AC signals through a cigarette lighter interface and extracts the AC features for frequency analysis through a signal conditioning circuit. The system employs a hybrid algorithm combining Fast Fourier Transform (FFT) and phase difference compensation to estimate the coarse frequency in the 1-second FFT analysis via sinusoidal least squares fitting and phase difference calculation. The STM32F4-based hardware integrates dual-channel acquisition and adaptive signal conditioning. The experimental results demonstrate high measurement accuracy with errors below 0.4%, real-time performance (1 Hz update rate), and operational portability. Validation tests show a 33-fold improvement in accuracy over the pure FFT method under transient conditions. Key innovations include (1) phase-difference-enhanced frequency resolution (0.1% error), and (2) optimized computational efficiency for embedded deployments. The system’s portability and robustness make it suitable for on-site diagnostics, meeting the automotive industry’s need for non-intrusive, high-precision speed measurements.
ISSN:2076-3417

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