Wheel Speed Sensor Interface Circuit Resistive Short Detection

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Solution Overview

Problem

Active wheel speed sensors in vehicles can experience temporary or permanent resistive shorts due to environmental factors, which corrupt wheel speed information and adversely affect anti-lock brake system (ABS) operation.

Innovation Solution

A method and apparatus for detecting and responding to resistive shorts in wheel speed sensors, involving a comparator circuit that compares sensor current to a threshold level, generating a wheel speed signal based on the lesser of high side and low side currents, and transmitting a flag to indicate the location of the short, ensuring accurate wheel speed information is provided to the ABS control module.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If wheel speed sensors are exposed to environmental factors (dirt, road salt, corrosion, water), then the sensors can detect wheel speed information, but resistive shorts may occur between terminals or to ground, corrupting the wheel speed information

Engineering Contradiction:

Improvewheel speed information accuracyVSAvoidresistive short from environmental factors

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent performs preliminary detection of resistive shorts by comparing high side and low side currents before the corrupt information affects ABS operation. The system proactively identifies the presence of a resistive short and takes corrective action by selecting alternative current measurements, preventing corrupted data from being processed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where the interface circuit continuously monitors current measurements from the wheel speed sensor, compares high side and low side currents, and adjusts its operation based on the detected conditions. When a resistive short is detected, the system feedbacks this information and switches to using the unaffected current measurement, maintaining accurate wheel speed information.

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If a resistive short occurs in the wheel speed sensor, then the sensor continues to operate, but the wheel speed information becomes corrupted and adversely affects ABS operation

Engineering Contradiction:

Improvesensor operation under fault conditionsVSAvoidwheel speed information accuracy

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent changes the operational parameters of the interface circuit by switching between different current measurement methods. When a resistive short is detected through parameter comparison (current magnitude analysis), the system changes from using one current measurement to another, effectively adapting to the fault condition and maintaining reliable operation.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful effect of a resistive short into a detectable condition. By monitoring for the presence of a resistive short through current comparison, the system identifies the fault and uses this information to select the unaffected current measurement, thereby converting a potentially harmful situation into a manageable condition that maintains system reliability.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Measurement precision

If the interface circuit monitors both high side and low side currents to detect resistive shorts, then accurate detection is achieved, but the device complexity increases

Engineering Contradiction:

Improveresistive short detection accuracyVSAvoidinterface circuit complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent makes the interface circuit multi-functional by using the same current monitoring and comparison circuitry for both normal operation and resistive short detection. The existing current measurements intended for wheel speed calculation are also utilized for fault detection, eliminating the need for separate detection circuitry and reducing overall system complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent merges the wheel speed measurement function with the resistive short detection function into a single integrated process. By combining these functions, the system achieves accurate fault detection without adding separate complex detection circuits, as the same current paths and comparison mechanisms serve dual purposes.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentEP3590776B1Resistive short circuit immunity for wheel speed sensor interface on braking system

Publication Date: 2022.03.30 NXP USA INC

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AI summary

An apparatus and method for resistive short circuit immunity for wheel speed sensor interface on a braking system. In one embodiment the apparatus includes a first circuit for generating a first periodic signal based on first current transmitted to a wheel speed sensor and a second circuit for generating a second periodic signal based on second current some or all of which is received from the wheel speed sensor. A circuit is provided for selecting the first periodic signal for output if a magnitude of the second current is greater than a magnitude of the first current, or the second periodic signal for output if magnitude of the second current is not greater than the magnitude of the first current. The selected first or second periodic signal contains information relating to a speed of a wheel that is associated with the wheel speed sensor.