Wheel Speed Sensor Interface Short Circuit Immunity
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Solution Overview
Problem
The existing ABS systems with active wheel speed sensors face issues with accurate wheel speed signal generation due to potential failures in primary wheel speed sensors or their interface circuits, leading to inaccurate data and increased system costs when redundant sensors are used.
Innovation Solution
The implementation of redundant wheel speed sensors and interface circuits with a short detection circuit to detect and prevent shorts, ensuring accurate wheel speed signal generation by selectively decoding currents based on predetermined thresholds and activating redundant circuits only when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant wheel speed sensors and interface circuits are implemented to ensure accurate wheel speed signal generation, then system reliability is improved, but device complexity and system cost increase
Solution Approach 1:
The interface circuit performs preliminary short detection on the sensor signal before processing wheel speed data. A short detection circuit monitors the sensor output for short conditions and generates a short detection signal that prevents erroneous wheel speed signals from being generated, thereby ensuring signal accuracy without requiring redundant sensors
Solution Approach 2:
The patent introduces an intermediary short detection circuit between the wheel speed sensor and the wheel speed signal generation circuit. This intermediary component detects shorts in the sensor signal and generates control signals that prevent inaccurate wheel speed signals from being produced, resolving the reliability-complexity contradiction by adding a targeted monitoring layer rather than full redundancy
2Measurement precision
If redundant wheel speed sensors are used to prevent signal inaccuracies, then measurement precision is improved, but system cost increases
Solution Approach 1:
The patent extracts the short detection function from the overall sensor system and implements it as a separate monitoring circuit within the interface unit. This allows the system to maintain measurement precision through active monitoring without duplicating the entire sensor assembly, thereby reducing the quantity of sensors required
Solution Approach 2:
Instead of copying the entire wheel speed sensor system, the patent implements a simplified short detection circuit that copies only the essential monitoring function. This detection circuit monitors sensor output for short conditions and generates control signals to prevent inaccurate measurements, achieving precision protection with minimal additional components
3Reliability
If short detection circuit is implemented to prevent inaccurate signals, then reliability is improved, but device complexity increases
Solution Approach 1:
The short detection circuit is merged with the existing interface circuit that connects the wheel speed sensor to the control system. The detection function is integrated into the interface unit's existing structure, sharing common components such as the microprocessor unit and signal processing pathways, thereby minimizing the increase in device complexity while improving reliability
Data Source
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AI summary
A method and apparatus for resistive short circuit immunity for wheel speed sensor interface on braking system. In one embodiment the apparatus includes a first circuit for transmitting a first current to a wheel speed sensor, and a second circuit for receiving a second current from the wheel speed sensor. Another circuit is coupled to the first and second circuits and configured to detect and respond to a near zero resistive short between the wheel speed sensor and ground. In this embodiment the circuit is configured to detect the near zero resistive short based on a direct or indirect comparison between magnitudes of the first and second currents to a first predetermined value, and based on a direct or indirect comparison between magnitudes of the first and second currents to a second predetermined value.