Yaw Moment Control Torque Allocation for Vehicle Stability
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Solution Overview
Problem
Conventional vehicle orientation control devices in four-wheel drive vehicles cause discomfort to drivers due to discontinuous changes in torque distribution between front and rear wheels when the sign of the actual yaw rate inverts, leading to unstable vehicle behavior.
Innovation Solution
A vehicle orientation control device that includes a standard yaw rate calculating unit, yaw rate sensor, target yaw moment calculating unit, braking and driving force commanding unit, and yaw moment control unit, which continuously adjusts the allocation ratio of yaw moment control torque to front and rear wheels based on the actual yaw rate within a predetermined region, ensuring smooth torque distribution and stabilizing vehicle orientation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the torque distribution to front and rear wheels is changed based on the deviation between target yaw rate and actual yaw rate, then the vehicle orientation can be stabilized, but the torque distribution changes discontinuously when the sign of actual yaw rate inverts, causing driver discomfort
Solution Approach 1:
The patent applies dynamics by making the front-rear torque distribution ratio variable and continuous rather than fixed or discontinuous. The allocation ratio is dynamically adjusted based on the actual yaw rate value, allowing smooth transitions as the yaw rate sign inverts. This continuous adaptation eliminates abrupt torque changes while maintaining effective yaw rate control, resolving the contradiction between orientation stability and driver comfort.
Solution Approach 2:
The patent changes the parameter of torque distribution allocation ratio from a fixed or discontinuous value to a continuously variable parameter. By making the allocation ratio depend on the actual yaw rate magnitude, the system achieves smooth torque transitions during sign inversions while maintaining the necessary torque distribution for orientation stability, thus eliminating driver discomfort.
2Reliability
If the front and rear driving forces are separately controllable to enable target yaw moment, then the vehicle behavior can be stabilized, but the discontinuous torque change causes discomfort to the vehicle driver
Solution Approach 1:
The system dynamically adjusts the torque distribution allocation ratio between front and rear wheels based on the actual yaw rate. This dynamic allocation ensures continuous and smooth torque changes during yaw rate sign inversions, eliminating the harmful discontinuous torque changes that cause driver discomfort while maintaining separate controllability of front and rear driving forces for stable vehicle behavior.
Solution Approach 2:
The patent introduces an intermediary mechanism - the continuous allocation ratio based on actual yaw rate - that mediates between the target yaw moment requirement and the actual torque distribution. This intermediary ensures smooth transitions during sign inversions, preventing direct discontinuous torque changes from reaching the wheels and thus eliminating driver discomfort while maintaining vehicle behavior stability.
Data Source
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AI summary
A vehicle orientation control device is provided in a four wheel drive vehicle capable of applying braking and driving force to each of the vehicle wheels. The vehicle orientation control device (24) is provided in a vehicle control device (10) for controlling the four wheel drive vehicle and includes a standard yaw rate calculating unit (25), a yaw rate sensor (22), a target yaw moment calculating unit (26), a braking and driving force commanding unit (15), and a yaw moment control unit (27). The yaw moment control unit (27) includes an allocation ratio varying unit (27a) for continuously changing the front and rear allocation ratio of the yaw moment control torque to be distributed to the front and rear wheels (3) and (2) in dependence on the detected actual yaw rate that is detected by the yaw rate sensor (22).