Vehicle Yaw Rate Control via Wheel Braking Torque
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Solution Overview
Problem
The conflict between reducing engine friction for lower fuel consumption and maintaining a desirable yaw rate for agile driving experiences, particularly for sporty driving styles, is unresolved in vehicles with low-friction internal combustion engines.
Innovation Solution
A method that triggers additional braking on at least one wheel during a load change to increase the yaw rate, compensating for reduced drag torque by applying braking torque that mimics the effect of higher drag torque, thereby stabilizing the vehicle and maintaining driving experience similar to older engines, while allowing vehicle drivers to select between sporty and comfort modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If engine friction is reduced to lower fuel consumption, then fuel efficiency is improved, but drag torque decreases causing insufficient yaw rate for agile driving
Solution Approach 1:
The brake system acts as an intermediary component to compensate for the reduced drag torque from low-friction engines. By applying targeted braking forces on individual wheels during cornering, the system generates the necessary yaw moment to maintain agile driving characteristics while allowing the engine to operate with minimal friction for optimal fuel efficiency.
Solution Approach 2:
The system dynamically changes the braking torque parameter based on driving conditions, vehicle speed, and cornering requirements. By adjusting the magnitude and distribution of braking forces in real-time, the system compensates for reduced engine drag torque while maintaining fuel efficiency benefits of low-friction engines.
2Speed
If additional braking is applied to increase yaw rate during load change, then driving agility is improved, but vehicle stability may deteriorate at high speeds
Solution Approach 1:
The braking system operates dynamically with continuously variable braking torques that adapt to current driving conditions. The control system adjusts braking intensity based on vehicle speed, steering angle, and lateral acceleration, ensuring that additional yaw rate is generated only when and where needed while maintaining vehicle stability across different operating conditions.
Solution Approach 2:
The system changes the braking torque parameter as a function of vehicle speed and lateral acceleration. At higher speeds, the braking torque is reduced or eliminated to prevent instability, while at lower speeds during cornering, increased braking torque provides the necessary yaw rate for agile driving.
3Force
If braking torque is increased to compensate for reduced drag torque, then yaw moment is improved, but energy loss from braking increases
Solution Approach 1:
Instead of applying braking force uniformly to all wheels, the system applies targeted braking forces only to specific wheels based on cornering direction and intensity requirements. This localized approach generates the necessary yaw moment while minimizing overall energy loss, as braking is applied only where and when needed to correct vehicle attitude.
Solution Approach 2:
The system applies partial braking action only on selected wheels rather than full braking on all wheels. This provides sufficient yaw moment to compensate for reduced drag torque while avoiding excessive energy loss that would result from applying full braking forces to all wheels simultaneously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method ensures vehicle stability and maintains a desirable yaw rate, providing drivers with the same driving experience as older engines with higher drag torque, while accommodating lower drag torque engines, and allows for different driving styles by adjusting braking torque based on vehicle speed and lateral acceleration.
Implementation Method 1
The friction in the engine causes the drag torque to be relatively high. Due to the fact that increasingly low-friction internal combustion engines have been built in recent years - also for the purpose of reducing carbon dioxide emissions - the magnitude of the drag torque has fallen increasingly.
Implementation Method 2
additional braking is triggered on at least one wheel when or as a result of the load change occurring. the braking torque applied to at least one wheel during the additional braking is determined as a function of measured values for at least one predetermined variable
Data Source
Figure 1~3
Figure 4
AI summary
The method involves checking occurrence of load exchange. The occurrence of the load exchange at a preset measurement value e.g. engine torque, and/or a preset change of the preset measurement value is detected. An additional brake at a wheel is released during the occurrence. A yaw rate delivered without the additional brake is increased. Braking torque applied by the additional brake at the wheel is fixed at a preset measurement variable e.g. vehicle transverse acceleration, based on the measurement value. The measurement value is a position of a drive actuation device, a deflection angle of a steering handling device, and a transverse acceleration. The measurement variable is a vehicle longitudinal velocity and a bend radius. An independent claim is also included for a motor vehicle.