Front-Rear Drive Force Allocation for Tire Slip and Yaw Control
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Solution Overview
Problem
Existing vehicle control systems fail to accurately manage driving/braking forces to prevent tire slip beyond the friction circle limit, leading to energy loss, noise, vibration, and unnatural deceleration due to excessive tire slip.
Innovation Solution
A driving/braking force control apparatus that includes a front-wheel longitudinal force generator, rear-wheel longitudinal force generator, tire slip angle and lateral force output units, slip ratio output units, tire lateral force change rate output units, and a target yaw moment setting unit, which dynamically control the output allocation ratio between the front and rear wheels based on tire slip angles, lateral forces, and slip ratios to maintain optimal driving/braking forces within the friction circle limit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If driving motors are controlled based on target driving torque to control vehicle behavior, then vehicle behavior control is achieved, but tire slip may exceed the friction circle limit causing energy loss, noise, vibration, and unnatural deceleration
Solution Approach 1:
The control apparatus calculates tire slip angles and lateral forces based on actual vehicle state (yaw rate, steering angle, vehicle speed) and uses this feedback to dynamically adjust the output allocation ratio between front and rear driving motors. This closed-loop feedback mechanism prevents tire slip from exceeding the friction circle limit by continuously monitoring and adjusting driving forces based on actual tire conditions.
Solution Approach 2:
The system dynamically adjusts the output allocation ratio between front and rear driving motors based on real-time tire slip conditions, slip angles, and lateral forces. This dynamic control adapts the driving force distribution to changing vehicle states, preventing excessive tire slip while maintaining effective vehicle behavior control throughout the maneuver.
2Reliability
If braking device is controlled based on target braking torque when tire force exceeds friction circle limit, then tire slip is reduced, but control complexity increases
Solution Approach 1:
The control apparatus replaces mechanical braking intervention with electronic control of the driving motors. Instead of using the braking device to correct excessive tire slip, the system adjusts the output allocation ratio between front and rear driving motors to prevent tire slip from exceeding the friction circle limit in the first place. This substitution simplifies the control system by eliminating the need for additional braking control mechanisms.
3Loss of energy
If output allocation ratio between front and rear driving motors is dynamically adjusted based on tire slip conditions, then energy loss is reduced, but control complexity increases
Solution Approach 1:
The control apparatus uses a unified control algorithm that simultaneously achieves multiple objectives: preventing tire slip from exceeding the friction circle limit, reducing energy loss, and maintaining vehicle behavior control. By calculating tire slip angles and lateral forces and using these to adjust the output allocation ratio, the system accomplishes multiple functions through a single integrated control mechanism rather than separate control systems for each objective.
Data Source
AI summary
A driving/braking force control apparatus includes a front-wheel longitudinal force generator, a rear-wheel longitudinal force generator, a tire slip angle output unit, a tire lateral force output unit, a slip ratio output unit, a tire lateral force change rate output unit, a target yaw moment setting unit, and a driving/braking force distribution control unit. The driving/braking force distribution control unit performs a control of an output allocation ratio between the front-wheel longitudinal force generator and the rear-wheel longitudinal force generator based on a target value of an additional yaw moment, a change rate of a tire lateral force of a front wheel to a slip ratio of the front wheel, and a change rate of a tire lateral force of a rear wheel to a slip ratio of the rear wheel.