Low-Mu Road Evaluation Device for Four-Wheel Drive Stability
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Solution Overview
Problem
Conventional low-μ road evaluation methods for four-wheel drive vehicles often result in evaluation errors due to sudden acceleration on dry roads or variations in driver acceleration, leading to frequent switching between four-wheel drive and two-wheel drive control, especially on roads with alternating low-μ and high-μ surfaces.
Innovation Solution
A low-μ road evaluation device that calculates a slip rate and low-μ information magnitude based on both wheel speed and acceleration operation, using preset threshold values to determine when to enable or disable low-μ road evaluation, thereby stabilizing control by considering the friction coefficient of the road surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If low-μ road evaluation is performed based simply on slip rate, then the evaluation responds quickly to wheel slip conditions, but evaluation errors occur on dry roads during sudden acceleration
Solution Approach 1:
The patent combines slip rate detection with acceleration operation detection to form a composite evaluation system. The low-μ information magnitude is calculated by integrating both slip rate magnitude and acceleration operation magnitude, preventing false evaluations during sudden acceleration on dry roads while maintaining quick response to actual low-μ conditions
Solution Approach 2:
The patent introduces a new parameter 'low-μ information magnitude' that changes based on the combination of slip rate and acceleration operation. This parameter dynamically adjusts the evaluation threshold, allowing the system to distinguish between genuine low-μ road conditions and temporary slip events during normal acceleration
2Adaptability or versatility
If low-μ road evaluation is performed based solely on acceleration operation, then the evaluation adapts to driver behavior, but errors occur due to variations in driver acceleration operations
Solution Approach 1:
The patent merges acceleration operation detection with slip rate detection to create a more robust evaluation system. By requiring both conditions to be satisfied simultaneously, the system filters out false positives caused by driver variation while maintaining adaptability to legitimate low-μ road conditions
Solution Approach 2:
The system uses feedback from both acceleration operation sensors and slip rate calculations to continuously refine the low-μ information magnitude. This dual-feedback mechanism allows the system to adapt to driver behavior patterns while maintaining precise friction coefficient estimation through cross-validation of both input signals
3Stability of the object's composition
If disabling methods are applied to prevent frequent switching, then control stability improves, but low-μ road evaluation may be disabled regardless of friction coefficient magnitude
Solution Approach 1:
The patent changes the disabling criterion from a fixed slip rate threshold to a friction coefficient-based threshold. The low-μ road evaluation is disabled only when the friction coefficient exceeds a predetermined threshold, ensuring that evaluation status changes are based on actual road conditions rather than temporary slip events, thus maintaining both stability and accuracy
Solution Approach 2:
The patent replaces the mechanical slip-rate-based disabling mechanism with a friction coefficient-based disabling mechanism. This substitution allows the system to maintain control stability by using the more accurate friction coefficient magnitude as the decision criterion, preventing inappropriate disabling of low-μ road evaluation
4Adaptability or versatility
If frequent switching between low-μ and high-μ evaluations occurs on alternating road surfaces, then the system responds to changing conditions, but stable control cannot be maintained
Solution Approach 1:
The patent changes the evaluation threshold from a fixed slip rate value to a dynamic friction coefficient-based threshold. This allows the system to maintain stability by using the friction coefficient magnitude as a stabilizing factor, preventing frequent switching while still responding appropriately to genuine changes in road conditions
Solution Approach 2:
The system performs preliminary calculation of the friction coefficient before making drive control decisions. By having the friction coefficient magnitude预先 calculated and available, the system can make more informed decisions about when to switch between evaluation modes, reducing unnecessary switching on alternating road surfaces while maintaining responsiveness to actual hazards
Data Source
AI summary
A power distribution control device 42 calculates a low-μ information magnitude, associated with the friction coefficient of the road surface, based on the slip rate and the vehicle acceleration operation magnitude. If the low-μ information magnitude exceeds an addition evaluation threshold, the power distribution control device 42 adds the low-μ information magnitude. If the low-μ information magnitude does not exceed the addition evaluation threshold, the power distribution control device 42 subtracts a constant K from a counter. The power distribution control device 42 makes evaluates a road to have a low-μ when the counter exceeds a low-μ evaluation threshold.