Torque Distributor Control via Yaw Rate Deviation
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Solution Overview
Problem
Existing torque distributors in four-wheel-drive vehicles face challenges in reducing operation noises and vibrations while maintaining driving performance, particularly on low-friction surfaces, as limiting command torque to reduce vibrations can hinder the vehicle's ability to transmit necessary torque for stability during side slipping or turning.
Innovation Solution
A control device for the torque distributor that uses yaw rate detection to limit and release command torque based on yaw rate deviation thresholds, ensuring necessary torque is transmitted to the rear wheels during unstable conditions, thereby reducing vibrations and noises while maintaining driving performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the command torque is limited to a predetermined limit value to reduce vibrations and noises, then the vibrations and noises from the torque distributor are reduced, but the driving performance and stability of the vehicle deteriorate under unstable running conditions
Solution Approach 1:
The command torque limit is made dynamic rather than static. The ECU dynamically adjusts whether to apply the torque limit based on real-time detection of yaw rate deviation. When the vehicle is in stable running condition (yaw rate deviation within threshold), the torque limit is applied to reduce vibrations. When the vehicle enters unstable condition (yaw rate deviation exceeds threshold), the torque limit is released to restore driving performance and stability.
Solution Approach 2:
The system implements feedback control by continuously monitoring the yaw rate deviation and using this information to adjust the torque distribution strategy. The ECU calculates the difference between actual yaw rate and ideal yaw rate, and based on this feedback, determines whether to limit or release the command torque, creating a closed-loop control system that adapts to changing vehicle conditions.
2Reliability
If the command torque is released from the limit value to maintain driving performance on low friction surfaces, then the driving performance and stability are improved, but the vibrations and noises from the torque distributor increase
Solution Approach 1:
The system dynamically switches between torque limiting and torque release modes based on vehicle running conditions. On low friction surfaces during unstable running (side slip, turning acceleration), the system releases the torque limit to provide sufficient restoring torque for stability. When the vehicle returns to stable running condition, the torque limit is re-applied to reduce vibrations and noises, creating an adaptive response to surface conditions.
Solution Approach 2:
The feedback mechanism continuously monitors yaw rate deviation to determine when torque limit release is necessary. When the yaw rate deviation exceeds the threshold, indicating unstable running on low friction surfaces, the feedback signal triggers torque limit release. When the deviation returns within the threshold, the feedback signal restores torque limiting, thereby managing the trade-off between performance and vibrations based on actual vehicle state.
Data Source
AI summary
A control device is disclosed for a torque distributor arranged between front and rear wheels that can achieve both reduction of vibrations and noises caused by torque transmitted to rear wheels by the torque distributor and securing of turning performance and driving performance. The control device is provided with a normative yaw rate calculation section for calculating a normative yaw rate that is a target value of a yaw rate when the vehicle turns and a yaw rate deviation calculation section for calculating a yaw rate deviation that is a difference between the normative yaw rate and the actual yaw rate. When the yaw rate deviation falls below a threshold Th1, a value of a command torque is limited to a predetermined limit torque value, and when the yaw rate deviation exceeds a threshold Th2, the limit of the command torque by a limit torque value is released.