ABS Vehicle Speed Estimation Under Wheel Lockup
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Solution Overview
Problem
Existing anti-lock braking systems (ABS) face challenges in accurately calculating vehicle speed and wheel slip rates due to wheel lockup, which can lead to loss of directional control and require additional sensors that may malfunction, making the system non-autonomous.
Innovation Solution
A method for calculating vehicle speed by monitoring wheel speed gradients and determining wheel lockup through gradient thresholds, ignoring locked wheel speeds, and correcting vehicle speed calculations using interpolation and averaging, without relying on inertial sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vehicle speed is calculated using wheel speed sensor signals during ABS regulation, then the calculation can be performed autonomously without additional sensors, but the accuracy deteriorates due to wheel lockup causing erroneous speed values
Solution Approach 1:
The patent extracts and removes erroneous speed values from locked wheels from the vehicle speed calculation. By detecting wheel lockup conditions and excluding these specific erroneous measurements, the system maintains autonomous operation while improving calculation accuracy through selective data exclusion.
Solution Approach 2:
The system uses feedback from wheel speed gradients to detect lockup conditions and dynamically adjusts the vehicle speed calculation by excluding affected wheels. This feedback mechanism allows the system to maintain accuracy while operating autonomously without additional sensors.
2Measurement precision
If inertial sensors are added to improve vehicle speed calculation accuracy, then measurement precision improves, but device complexity and system reliability worsen due to additional failure points
Solution Approach 1:
The system uses existing wheel speed sensor data and gradient calculations to self-diagnose and self-correct vehicle speed calculation errors. By leveraging its own operational data to detect and exclude lockup conditions, the system achieves improved accuracy without adding external sensors or increasing complexity.
3Device complexity
If wheel lockup detection is delayed, then the system can operate with simpler detection logic, but directional control is lost during the delay period
Solution Approach 1:
The system performs preliminary detection of wheel lockup conditions by continuously monitoring wheel speed gradients before complete lockup occurs. This early detection allows the ABS system to take preventive action, maintaining directional control by addressing the lockup condition before it fully develops.
Data Source
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AI summary
In this method for calculating a speed (VS) of a vehicle comprising at least two wheels (W1, W2), the following steps are implemented: a. the respective speeds (WS1, WS2) of at least two wheels of the vehicle are measured, b. a test is carried out to determine if at least one of the wheels is locked up, and – if at least one of the at least two wheels is locked up and at least one of the two wheels is not locked up, the speed of the vehicle is calculated without using the measured speed of the locked-up wheel; or – if the at least two wheels are locked up, the speed of the vehicle is calculated by linear extrapolation from at least two known earlier speeds of the vehicle, finally – if none of the least two wheels is locked up, the speed of the vehicle is calculated using all of the measured speeds of the wheels.