4WD Vehicle Speed Estimation Across Traction-Anti-Skid Switching
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Solution Overview
Problem
In four-wheel drive vehicles, switching from traction control to anti-skid control results in a decrease in vehicle body speed estimation accuracy due to wheel speed overshoot, which existing methods fail to address effectively.
Innovation Solution
The method for selecting wheel speed for vehicle body speed estimation is switched between select-low and select-high based on the sign of drive torque and the convergence of wheel speeds within specific ranges, using a control system that adjusts torque application and wheel speed correction to minimize the impact of overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the method for selecting wheel speed is switched from select-low to select-high at the same time as switching from traction control to anti-skid control, then the control response is improved, but the estimation accuracy of vehicle body speed decreases due to wheel speed overshoot
Solution Approach 1:
The patent applies preliminary action by monitoring wheel speed convergence status before switching the selection method. The control system checks whether wheel speeds have converged within a predetermined range before transitioning from select-low to select-high method, ensuring the switch occurs at the optimal moment to avoid estimation errors caused by overshoot while maintaining responsive control.
2Adaptability or versatility
If the wheel speed selection method is switched immediately upon control mode change, then the system adaptability is improved, but the estimation accuracy deteriorates due to overshoot influence
Solution Approach 1:
The patent implements dynamics by making the wheel speed selection method adaptive rather than static. The system dynamically adjusts the selection method (select-low or select-high) based on real-time wheel speed convergence status and control mode, allowing the system to maintain high adaptability while avoiding the pitfalls of premature switching that would reduce estimation accuracy.
3Measurement precision
If wheel speed convergence is monitored before method switching, then the estimation accuracy is improved, but the control complexity increases
Solution Approach 1:
The patent applies feedback by continuously monitoring wheel speed convergence status and using this information to determine when to switch the selection method. This feedback mechanism ensures accurate estimation by switching only when wheel speeds have converged, while the automated nature of the feedback loop prevents excessive complexity in the control system.
Data Source
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AI summary
When the sign of the drive torque that is applied to wheels 1 is reversed and an absolute value difference of at least two of the wheel speeds becomes smaller than a threshold value ε, an ECU 3 switches the method for selecting the wheel speed used for estimating the vehicle body speed between select-low and select-high.