Four-Wheel Drive Torque Distribution Control via Rotational Speed Feedback
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Solution Overview
Problem
Existing four-wheel drive vehicle systems face challenges in accurately controlling driving force distribution between front and rear wheels, particularly in adapting to variations in tire diameters and sensor errors, which affect traction performance and controllability during turns.
Innovation Solution
A driving force distribution control apparatus that includes a theoretical value calculator, a normative value calculator, and a servo controller, which calculates primary and secondary rotational speed theoretical values based on steering angle, vehicle speed, and yaw rate, and corrects the driving force distribution using servo control to achieve optimal rotational difference normative values, thereby improving traction and controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If driving force distribution control is performed based on rotational speed difference between front and rear wheels, then traction performance is improved, but accuracy deteriorates due to tire diameter variations and sensor errors
Solution Approach 1:
The control apparatus calculates a normative rotational speed difference value based on theoretical calculations considering steering angle, vehicle speed, and yaw rate, then compares this with the actual measured rotational speed difference. The difference between normative and actual values is fed back to correct the driving force distribution control, thereby compensating for measurement errors and improving accuracy.
Solution Approach 2:
The system changes the control parameter from directly using measured rotational speed difference to using a corrected value that combines theoretical calculation with measurement compensation. The normative value calculation incorporates multiple parameters (steering angle, vehicle speed, yaw rate) to dynamically adjust the target rotational speed difference, improving adaptability and accuracy.
2Adaptability or versatility
If torque split clutch is used to divide driving force between front and rear wheels, then four-wheel drive capability is improved, but control accuracy deteriorates due to inability to precisely compensate for tire diameter differences
Solution Approach 1:
The system implements feedback control by continuously comparing the actual rotational speed difference between front and rear wheels with the normative value calculated from vehicle dynamics parameters. The torque split clutch control is adjusted based on the deviation between actual and normative values, enabling precise compensation for tire diameter differences and improving driving force distribution accuracy.
Solution Approach 2:
The patent replaces purely mechanical torque split control with a control system that incorporates theoretical calculations and feedback mechanisms. By substituting mechanical direct control with a system that uses normative value calculation and deviation correction, the accuracy of driving force distribution is significantly improved while maintaining four-wheel drive capability.
Data Source
AI summary
A driving force distribution control apparatus for a four-wheel drive vehicle includes a theoretical value calculator, a normative value calculator, and a servo controller. The theoretical value calculator is configured to calculate a primary rotational speed theoretical value of primary drive wheels and a secondary rotational speed theoretical value of secondary drive wheels based on a steering angle, a vehicle speed, a yaw rate, and a slip angle of the four-wheel drive vehicle and configured to calculate a rotational difference normative theoretical value indicating a difference between rotational speed theoretical values of input and output shafts of a drive force distribution apparatus using the primary rotational speed theoretical value and the secondary rotational speed theoretical value.