4WD Vehicle Speed Estimation During Wheel Speed Overshoot
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Solution Overview
Problem
In four-wheel drive vehicles, the accuracy of vehicle body speed estimation decreases when switching from traction control to anti-skid control due to overshoot of wheel speed, and existing methods do not provide effective solutions for this issue.
Innovation Solution
The method for selecting wheel speed used for estimating vehicle body speed 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 corrects wheel speeds and determines convergence status 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 deviation before switching control methods. When the deviation exceeds a threshold, the system prepares for potential overshoot by adjusting the wheel speed selection method in advance, rather than switching immediately upon control mode change. This proactive approach prevents estimation accuracy degradation while maintaining responsive control switching.
Solution Approach 2:
The patent implements dynamics by making the wheel speed selection method adaptive rather than static. The system dynamically switches between select-low and select-high methods based on real-time wheel speed deviation conditions. This dynamic adaptation allows the system to optimize between response speed and estimation accuracy depending on the current operational state, resolving the contradiction between these two requirements.
2Productivity
If wheel speed selection method is switched immediately with control mode, then control switching efficiency is improved, but estimation accuracy deteriorates due to overshoot influence
Solution Approach 1:
The patent employs feedback by continuously monitoring wheel speed deviation and using this information to determine when to switch the wheel speed selection method. Rather than switching blindly with control mode, the system waits for feedback indicating that wheel speeds have converged sufficiently. This feedback mechanism ensures accurate switching timing, maintaining both high switching efficiency and estimation accuracy.
Solution Approach 2:
The patent applies parameter changes by adjusting the wheel speed selection parameter (select-low vs. select-high) based on the convergence state of wheel speeds. The system changes this parameter dynamically according to measured wheel speed deviations, allowing optimal balance between switching efficiency and estimation accuracy without immediate switching.
3Device complexity
If wheel speed overshoot is not corrected, then the control system remains simple, but the vehicle body speed estimation accuracy decreases
Solution Approach 1:
The patent applies local quality by implementing a targeted correction approach rather than a comprehensive complex system. The correction mechanism specifically addresses wheel speed overshoot in the context of control mode switching, applying selectivity to when and how corrections are made. This localized approach improves estimation accuracy without requiring complex system-wide changes.
Data Source
AI summary
A vehicle body speed estimation device and a vehicle body speed estimation method are provided for estimating a vehicle body speed of a four-wheel drive vehicle from a wheel speed of each wheel of the four-wheel drive vehicle. In the vehicle body speed estimation device and a vehicle body speed estimation method, a controller determines whether a deviation of at least two of the wheel speeds among the wheel speeds is within a first prescribed range. The controller switches a method for selecting the wheel speed used for estimating the vehicle body speed between a first method and a second method when a sign of a drive torque that is applied to each of the wheels is reversed and the deviation of at least two of the wheel speeds among the wheel speeds is within the first prescribed range.