Rear Wheel Brake Torque for Aquaplaning Directional Control
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Solution Overview
Problem
During aquaplaning, vehicles become unmanageable as the front wheels lose traction, making it impossible for drivers to steer the vehicle, leading to potential accidents due to the inability of existing driver assistance systems to effectively control the vehicle's direction.
Innovation Solution
The method involves detecting aquaplaning conditions and applying targeted braking interventions on the rear wheels to create directional control, where the brake pressure is set based on the driver's steering request, allowing the vehicle to be steered by simulating the effect of steering wheel turns through differential braking torque on the rear wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ESC systems intervene by reducing vehicle speed through engine and brake interventions, then vehicle stability is improved, but directional control capability deteriorates when front wheels lose traction during aquaplaning
Solution Approach 1:
The patent inverts the conventional steering approach by using rear wheel braking instead of front wheel steering to achieve directional control. When front wheels lose traction during aquaplaning, the system applies differential braking torque to the rear wheels, creating a yaw moment that changes the vehicle's direction of travel. This inverse approach allows the vehicle to be steered through the rear axle rather than the front axle.
Solution Approach 2:
The patent introduces a control system that acts as an intermediary between the driver's steering input and the vehicle's actual movement. The system detects aquaplaning conditions and translates the driver's steering wheel angle into appropriate rear wheel braking interventions, mediating the control action to achieve the desired directional change despite front wheel slippage.
2Ease of operation
If front wheels are used for steering during aquaplaning, then directional control is possible under normal conditions, but control effectiveness deteriorates when water film causes loss of traction
Solution Approach 1:
The patent segments the vehicle's steering function into two independent parts: front wheel steering for normal conditions and rear wheel braking for aquaplaning conditions. By separating these functions and using different mechanisms for each condition, the system maintains directional control capability across varying traction conditions without relying solely on front wheel steering.
Solution Approach 2:
The patent changes the control parameter from front wheel steering angle to rear wheel braking torque when aquaplaning is detected. The control system monitors wheel speed differences and steering wheel angle, then transforms the control action into differential braking torque applied to the rear wheels, adapting the control mechanism to the current traction conditions.
3Ease of operation
If targeted braking intervention is applied to rear wheels to enable steering during aquaplaning, then directional control is restored, but system complexity increases compared to conventional ESC interventions
Solution Approach 1:
The patent makes the existing brake system multi-functional by using it for both conventional speed control (ESC function) and directional control (steering function). The same rear wheel brakes that are already part of the vehicle's braking system are utilized to generate yaw moments for directional changes, eliminating the need for separate steering actuators or additional control mechanisms.
Solution Approach 2:
The control system uses the vehicle's existing components and sensors to achieve the steering function. The wheel speed sensors already present for ABS/ESC purposes are used to detect aquaplaning conditions, and the brake system already integrated into the vehicle is used to provide the steering action, allowing the system to serve multiple functions with existing infrastructure.
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 approach enables the vehicle to remain steerable during aquaplaning conditions, preventing accidents by effectively changing the vehicle's direction in response to the driver's inputs, even when front wheels are unable to transmit cornering forces, thus maintaining control and safety.
Implementation Method 1
the forces that can be transmitted between the respective vehicle tire and the road surface... the cornering forces or transverse forces can decrease
Data Source
Figure 1~3
AI summary
Disclosed are a method and an device for assisting drivers in the event of aquaplaning on a road surface on which a vehicle travels; at least one variable relating to vehicle dynamics is used to verify whether an aquaplaning event is occurring, and if if an aquaplaning event is acknowledged, an intervention is performed on a rear wheel brake (42, 46) in order to change directions, the brake pressure being adjusted in accordance with a steering maneuver desired by the driver.