Rear-Wheel Torque Control for EV Yaw Stability on Low-Friction Roads
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Solution Overview
Problem
Electric vehicles face significant disturbances in vehicle behavior when transitioning from deep snow conditions to low-friction roads due to unintended wheel slipping, leading to rear wheel side-to-side swinging.
Innovation Solution
The electric vehicle is equipped with a yaw rate sensor and processor that control the torques of right and left rear wheels based on measured yaw rates to suppress wheel slipping, using a control algorithm to maintain vehicle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the right and left rear wheels are allowed to slip at high speed to clear snow, then the vehicle can escape from deep snow conditions, but the vehicle experiences significant disturbances and rear wheel side-to-side swinging when transitioning to low-friction roads
Solution Approach 1:
The control device uses yaw rate sensor information to detect vehicle body rotation and dynamically adjusts the torque distribution between right and left rear wheels. This feedback mechanism allows the system to maintain high wheel rotation speeds for snow clearance while automatically correcting unintended vehicle behavior and rear wheel swinging through real-time torque suppression on the outer rear wheel during transitions to low-friction roads
Solution Approach 2:
The system changes the torque parameter applied to the rear wheels based on detected vehicle conditions. When snow clearance is needed, high torque is applied to enable wheel slip. When transitioning to low-friction roads and vehicle instability is detected, the system suppresses torque on the outer rear wheel to eliminate side-to-side swinging, thus adapting the torque parameter to maintain both speed and stability
2Power
If high torque is applied to both rear wheels to enable intentional slipping for snow clearance, then the wheels can rotate at high speed, but unintended wheel slipping occurs causing rear wheel side-to-side swinging on low-friction roads
Solution Approach 1:
Instead of applying uniform torque to both rear wheels, the system applies different torque levels to the right and left rear wheels based on local conditions. When vehicle instability is detected on low-friction roads, the system selectively suppresses torque only on the outer rear wheel (the one causing side-to-side swinging), while maintaining torque on the inner rear wheel. This local differentiation eliminates unintended slipping and rear wheel swinging while preserving the power needed for snow clearance
Data Source
AI summary
An electric vehicle includes a yaw rate sensor and a processor. The yaw rate sensor is configured to measure a yaw rate of a vehicle body in a vehicle. The processor is configured to control respective torques of right and left rear wheels coupled to respective motors of the electric vehicle. In a case where a mode that allows the right and the left rear wheels to slip is selected as a traveling mode of the vehicle, the processor is configured to perform a control to suppress one of the torques of the right and the left rear wheels on a basis of the yaw rate measured by the yaw rate sensor.