In-Wheel Motor Torque Control for Vehicle Turning Stability
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Solution Overview
Problem
Conventional in-wheel systems face challenges in maintaining turning stability and minimizing the radius of rotation due to limitations in the Ackerman rate, leading to tire drag and degraded steering sensing, especially when the steering angle is small and tire slip occurs.
Innovation Solution
A control unit determines the turning mode based on vehicle driving information and calculates the present Ackerman rate to generate control commands for each wheel's motor, allowing independent torque control to improve turning stability and minimize the radius of rotation by adjusting the torque distribution between the outer and inner wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the steering angle is increased to minimize the radius of rotation, then the radius of rotation is reduced, but the Ackerman rate increases excessively which degrades steering sensing and causes tire drag
Solution Approach 1:
The system dynamically adjusts the Ackerman rate parameter based on vehicle speed and steering angle conditions. At low speeds, the Ackerman rate is increased to minimize turning radius, while at higher speeds it is reduced to maintain steering sensing accuracy and prevent tire drag. This parameter adaptation resolves the contradiction by optimizing the Ackerman geometry for different operating conditions.
2Stability of the object's composition
If the Ackerman rate is increased to improve turning stability, then turning stability is enhanced, but the radius of rotation increases
Solution Approach 1:
The system implements dynamic control of the Ackerman rate rather than using a fixed value. The control unit adjusts the Ackerman rate in real-time based on vehicle speed, steering angle, and desired turning performance. This allows the system to achieve high turning stability when needed while minimizing turning radius when required, resolving the contradiction through dynamic adaptation.
3Measurement precision
If the steering angle is kept small for normal driving, then steering precision is maintained, but the Ackerman rate falls and turning performance degrades
Solution Approach 1:
The system changes the Ackerman rate parameter based on the relationship between steering angle and vehicle speed. When the steering angle is small but the vehicle speed is low (such as during slow maneuvering), the system increases the Ackerman rate to improve turning performance without requiring a large steering angle. This resolves the contradiction by decoupling turning performance from steering angle magnitude through parameter adaptation.
Data Source
AI summary
Disclosed is a system and method for controlling a vehicle using an in-wheel system which controls a motor mounted in each wheel of the vehicle independently. More specifically, a control unit is configured to determine a turning mode of the vehicle based on vehicle driving information, calculate a present Ackerman rate of the vehicle based on the determined turning mode, generate a control command based on the present Ackerman rate, and control the motor of each wheel using the control command, independently.