4WD Vehicle Speed Estimation Under All-Wheel Slip
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Solution Overview
Problem
In four-wheel drive vehicles, the estimated vehicle body speed based on wheel speeds is higher than the actual speed when all wheels are in slip, leading to decreased accuracy in vehicle control and information processing.
Innovation Solution
A vehicle body speed estimation method that acquires estimated speed based on wheel speeds or longitudinal acceleration, performs torque limitation on specific wheels when the estimated speed exceeds a determined threshold, and stops the limitation when the actual speed is confirmed to be within a safe range, ensuring accurate speed estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If vehicle body speed is estimated based on wheel speeds, then the estimation is simple and responsive, but the estimated speed becomes higher than actual speed when wheels are in slip, reducing accuracy
Solution Approach 1:
The system continuously monitors wheel acceleration and estimated vehicle body speed, and when slip conditions are detected (wheel acceleration > 0 and estimated speed exceeds operation determination speed), feedback control is applied through torque limitation to correct the deviation between estimated and actual speed
Solution Approach 2:
The system changes the torque parameter of drive wheels dynamically based on slip detection. When slip is detected, torque is limited to reduce wheel acceleration, which in turn reduces the deviation between wheel speed-based estimation and actual vehicle body speed
2Measurement precision
If torque limitation is applied continuously to prevent speed estimation deviation, then estimation accuracy is maintained, but unnecessary torque limitation occurs when slip is not present, affecting vehicle performance
Solution Approach 1:
The torque limitation is applied dynamically based on real-time detection of slip conditions. The system monitors wheel acceleration and estimated speed continuously, applying torque limitation only when slip conditions are detected (wheel acceleration > 0 and estimated speed > operation determination speed), and releasing it when stop conditions are met, thereby avoiding unnecessary torque limitation that would degrade vehicle performance
3Measurement precision
If torque limitation is applied to reduce estimated speed deviation, then speed estimation accuracy improves, but the system complexity increases due to additional control logic
Solution Approach 1:
The control logic is segmented into distinct functional modules: wheel acceleration detection unit, operation condition determination unit (comparing estimated speed with operation determination speed), torque limitation execution unit, and stop condition determination unit. This modular segmentation makes the complex control system more manageable and implementable while maintaining the ability to correct speed estimation deviations
Data Source
AI summary
A vehicle body speed estimation method applied to a four-wheel drive vehicle includes: acquiring an estimated vehicle body speed based on wheel speeds or a longitudinal acceleration of the vehicle; determining whether an operation condition that includes at least a condition that the estimated vehicle body speed is higher than an operation determination speed is satisfied; performing torque limitation to reduce a torque of a portion of wheels of the vehicle when the operation condition is satisfied; determining whether a stop condition that includes a condition that the estimated vehicle body speed is lower than or equal to a stop determination speed or a condition that a duration of a state where a wheel acceleration of the portion of the wheels is higher than zero is longer than or equal to a set period of time; and stopping the torque limitation when the stop condition is satisfied.