Wheel Speed Sensor Signal Processing Error Compensation
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Solution Overview
Problem
The complexity of wiring harnesses in anti-lock braking systems leads to noisy current-domain signals, causing errors in wheel speed measurements due to capacitive interference and multiple wire functionalities, necessitating an improved measurement system.
Innovation Solution
A circuit comprising a power terminal, sensing circuitry, a state machine, pulse width counter, error counter, and pulse width calculator that converts current-domain signals to voltage-domain, compares signals to thresholds, and calculates accurate pulse widths by removing errors, thereby enhancing wheel speed measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If current-domain signals are used for communication through power cables, then wire complexity is reduced and multiple functions are achieved, but measurement precision deteriorates due to noisy signals and capacitive interference
Solution Approach 1:
The patent introduces an intermediary error compensation mechanism that mediates between the noisy current-domain signal and the final measurement result. The error counter captures the capacitive interference and aging effects, then compensates for these errors in the pulse width calculation, effectively isolating the true wheel speed measurement from the noisy communication channel.
Solution Approach 2:
The patent changes the measurement parameter from direct pulse width measurement to error-compensated pulse width measurement. By introducing error counters that measure the deviation caused by capacitive effects and aging, the system transforms the measurement process to account for these parameter changes, thereby maintaining precision despite using simplified wiring.
2Quantity of substance
If power cables with multiple functions are used, then the number of wires is reduced, but signal noise increases due to capacitive interference
Solution Approach 1:
The patent converts the harmful capacitive interference into a measurable error parameter. Instead of trying to eliminate the noise, the error counter captures and quantifies the noise effect, then uses this information to compensate for the distortion in the final measurement, effectively turning the harmful noise into a correctable parameter.
Solution Approach 2:
The system implements feedback by continuously monitoring the signal distortion through error counters and using this information to adjust the final pulse width calculation. The error compensation mechanism provides feedback about the noise level and capacitive effects, allowing the system to dynamically correct for these disturbances in real-time.
3Measurement precision
If error compensation is implemented, then measurement accuracy is improved, but device complexity increases
Solution Approach 1:
The patent segments the measurement process into distinct functional blocks: sensing circuitry for signal acquisition, state machine for control, pulse width counter for basic measurement, error counter for distortion capture, and pulse width calculator for final computation. This segmentation allows each component to perform a specific function with simple logic, making the overall complex system manageable and implementable using standard digital circuit components.
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 solution reduces measurement errors and provides more accurate wheel speed data transmission, accounting for capacitive changes and aging-related issues, resulting in a more robust and reliable system.
Implementation Method 1
a current-to-voltage (I-to-V) converter that converts the sensor signal pulses into the voltage-domain from the current-domain
Data Source
AI summary
Anti-lock and intelligent braking systems have become ubiquitous in modern vehicles, which employ wheel speed sensors or WSSs. These WSSs generally uses current-domain signals (transmitted through power wires) to reduce the size of the vehicle's wiring harness, but because a vehicle is an inherently noisy environment, mixed signal circuit or MSC (used to decode these signals for a microcontroller) should be able to filter out or compensate for noise. However, traditional MSCs have been plagued with problems, partly due to errors in time base measurement due to noise (as well as other factors). Here, an MSC is provided that accurately calculates a wheel speed pulse width (which is used for time base measurements) by observing the wheel speed pulse as it passes through several thresholds.