Wheel Torque Recovery Control Using Wheel Speed Sign Changes
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Solution Overview
Problem
Existing vehicle stability and traction control systems face challenges in efficiently adjusting wheel torque to match driver demand after reducing torque to manage wheel slip, leading to prolonged drivability issues and potential reintroduction of slip conditions.
Innovation Solution
A method for adjusting wheel torque by increasing the rate of torque toward driver demand based on the count of changes in wheel speed signs, using a controller to detect wheel slip more sensitively and accurately, allowing for faster recovery from torque reduction without reintroducing slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wheel torque is reduced to manage wheel slip, then wheel slip is controlled and vehicle stability is maintained, but the time to return to driver demand wheel torque is prolonged
Solution Approach 1:
The patent applies dynamics by making the torque adjustment rate variable rather than fixed. The controller dynamically adjusts the rate at which wheel torque is increased based on real-time detection of wheel slip conditions and road surface friction characteristics. This allows the system to recover torque faster when safe to do so, while preventing reintroduction of slip when road conditions are marginal, thus resolving the contradiction between quick recovery and slip prevention.
Solution Approach 2:
The patent implements feedback by continuously monitoring wheel speed, calculating wheel slip, and using this information to adjust the torque recovery rate. The system detects when wheel slip is occurring or about to occur during torque recovery and adjusts the recovery rate accordingly. This closed-loop feedback mechanism enables the controller to optimize the balance between returning torque quickly to driver demand and preventing reintroduction of wheel slip.
2Ease of operation
If wheel torque is increased quickly toward driver demand, then drivability is improved, but wheel slip may be reintroduced
Solution Approach 1:
The system dynamically adjusts the torque recovery rate based on detected wheel slip conditions and estimated road surface friction. When the controller detects signs of wheel slip or marginal traction conditions, it reduces the torque recovery rate to prevent reintroduction of slip. When conditions are favorable, it increases the recovery rate to quickly restore drivability. This dynamic adjustment resolves the contradiction by making the torque increase rate adaptive to real-time road conditions.
Solution Approach 2:
The patent applies preliminary anti-action by detecting early signs of wheel slip or potential slip conditions during torque recovery and taking corrective action before full slip occurs. The controller monitors wheel speed changes and other parameters to anticipate slip conditions, then adjusts the torque recovery rate proactively to prevent slip from developing. This preventive approach maintains drivability while avoiding the harmful effects of wheel slip.
3Device complexity
If traditional slip detection methods are used, then system complexity is reduced, but detection precision and accuracy are insufficient
Solution Approach 1:
The patent replaces traditional mechanical or simple threshold-based slip detection methods with a more sophisticated detection system that uses multiple parameters including wheel speed, vehicle longitudinal acceleration, and calculated friction coefficients. This substitution enables more accurate detection of wheel slip conditions and road surface characteristics without requiring additional complex mechanical sensors, thus improving measurement precision while keeping the system relatively simple.
Solution Approach 2:
The patent makes the existing wheel speed sensor and controller serve multiple functions: not only basic speed measurement but also precise wheel slip detection, road surface friction estimation, and torque recovery rate determination. By making the control system multi-functional, the patent improves detection precision using existing hardware, avoiding the need for additional complex detection equipment while enhancing the accuracy of slip detection and torque control.
Data Source
AI summary
Methods and systems for adjusting wheel torque to a driver demand wheel torque after the wheel torque has been reduced below the driver demand wheel torque are described. In one example, a rate at which wheel torque is returned to driver demand wheel torque is based on sign changes for wheel speed.