Vehicle Braking Force Control for Load Shift Stabilization
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Solution Overview
Problem
Conventional braking force control systems for vehicles experience wobbling and roll behavior deterioration due to unintended yaw rates during high-speed braking, as they fail to effectively manage the difference in ground contact loads between the left and right wheels, leading to control lag and instability.
Innovation Solution
A braking force control apparatus and method that individually control the braking forces applied to the rear wheels to equalize their wheel speeds based on a predetermined relationship with the front wheels, while correcting the target wheel speed of at least one rear wheel on the ground contact load increase side to be less than the load decrease side, using parameters like yaw acceleration, roll rate, and lateral jerk to phase-correct the braking forces and reduce unintended yaw rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional front-rear braking force distribution control is performed without correcting for load shift, then the control system remains simple and responsive, but the vehicle experiences wobble and roll behavior deterioration due to unintended yaw rates
Solution Approach 1:
The control system performs preliminary detection of load shift amount and change rate, then proactively corrects the target wheel speed before unintended yaw rates develop. This predictive approach prevents vehicle wobble and roll behavior deterioration while maintaining a relatively simple control structure.
Solution Approach 2:
The system continuously monitors load shift amount and change rate, feeds this information back to the controller, and dynamically adjusts the target wheel speed of rear wheels. This closed-loop feedback mechanism enhances vehicle stability during braking without requiring complex additional hardware.
2Reliability
If the target wheel speed is corrected based on load shift change rate, then unintended yaw rates are reduced and vehicle wobble is restrained, but the control calculation complexity increases
Solution Approach 1:
The control system utilizes existing sensor data (wheel speeds, braking forces) to calculate load shift amount and change rate through mathematical relationships rather than requiring additional dedicated sensors. This self-service approach reduces braking stability issues while avoiding increased measurement complexity.
Solution Approach 2:
The system dynamically adjusts the target wheel speed parameter based on calculated load shift characteristics. By changing this key control parameter in response to detected load conditions, the system achieves improved braking stability without adding complex detection or control mechanisms.
3Speed
If braking forces are applied to equalize wheel speeds without considering load shift dynamics, then the control response is fast, but the vehicle tends to turn toward the side with smaller ground contact load causing wobble
Solution Approach 1:
The control system calculates the load shift amount and change rate before finalizing the target wheel speed assignment. This preliminary analysis allows the system to anticipate directional stability issues and adjust braking forces proactively, preventing unintended vehicle turning while maintaining fast response characteristics.
Solution Approach 2:
The system applies asymmetric correction to the target wheel speeds of left and right rear wheels based on the direction and magnitude of load shift. By creating deliberate asymmetry in the control parameters that counteracts the load shift effect, the system maintains vehicle directional stability during rapid braking response.
Data Source
AI summary
A vehicle braking force control apparatus includes a controller that performs a front-rear braking force distribution control in which the braking forces applied to the left and right rear wheels are controlled individually so that a wheel speed of each of the rear wheels is equal to a target wheel speed of the rear wheel, which is set based on a predetermined relationship between the wheel speed of the front wheel and the target rear wheel speed of the rear wheel, and that corrects the target wheel speed of at least one of the left and right rear wheels, based on a parameter related to a change rate of load shift amount in a vehicle transverse direction, so that the target wheel speed of the rear wheel on a ground contact load increase side is less than the target wheel speed of the rear wheel on a ground contact load decrease side.