Brake Pedal Stroke Control for Stable Brake-By-Wire Feel
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Solution Overview
Problem
Conventional brake-by-wire systems experience unstable braking forces due to variations in driver pedaling force, leading to stressful and intricate brake pedal operations, which can result in unintended acceleration or deceleration, affecting passenger comfort and safety.
Innovation Solution
A brake system with an electronic control unit that allows drivers to select between a first mode for normal control and a second mode, where automatic braking force control is executed when the brake pedal stroke is between specific thresholds, maintaining a constant braking force and transitioning back to normal control at higher pedal strokes, thereby simplifying the operation and enhancing stability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If automatic braking force control is executed to maintain constant braking force, then braking stability is improved, but driver's feeling of brake pedal operation is lost
Solution Approach 1:
The system dynamically switches between two control modes based on pedal stroke amount: automatic braking force control mode (for stable braking) and normal control mode (for driver feel). This dynamic switching resolves the contradiction by applying different control strategies at different operating conditions.
Solution Approach 2:
The brake pedal stroke range is segmented into multiple regions: first region (normal control), second region (automatic control with constant braking force), and third region (normal control again). This segmentation allows the system to apply automatic control only in the intermediate range where it provides benefit while preserving driver feedback at low and high stroke amounts.
2Ease of operation
If normal control is executed based on basic characteristics, then driver's brake pedal operation feel is maintained, but braking force becomes unstable due to pedaling force variations
Solution Approach 1:
The ECU acts as an intermediary that monitors pedal stroke amount and automatically compensates for pedaling force variations by controlling brake fluid pressure, while still allowing normal control to operate in regions where driver feel is prioritized. This intermediary control resolves the contradiction by selectively applying corrections.
Solution Approach 2:
The system changes the control parameter from direct pedal force response to pedal stroke amount-based control in the intermediate region, maintaining a predetermined braking force regardless of pedaling force variations, thereby stabilizing braking output while preserving driver feel at extreme positions.
3Stability of the object's composition
If automatic braking force control is executed in the intermediate stroke range, then braking stability is improved, but device complexity increases
Solution Approach 1:
The ECU performs multiple functions: it monitors pedal stroke amount, determines which control region is active, executes appropriate control algorithms, and manages mode transitions. This multi-functionality reduces the need for separate dedicated components for each control function, thereby limiting the increase in device complexity.
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
The system enables stable and comfortable braking with reduced driver stress by maintaining constant braking force within specified thresholds, ensuring maximum braking force is achieved without compromising the feel of the brake pedal operation, thus enhancing safety and reliability.
Implementation Method 1
a sensor that outputs a signal corresponding to a stroke amount of the brake pedal
Implementation Method 2
The brake circuit generates braking force to apply a brake to a vehicle by supplying hydraulic pressure to wheel cylinders provided to respective wheels
Data Source
AI summary
A brake system includes a brake device, a brake circuit that generates a braking force for braking a vehicle, ECU that controls the braking force generated by the brake circuit according to a stroke amount of the brake pedal, and a user interface. When the first mode is selected, the ECU executes normal control for controlling the braking force generated by the brake circuit based on a basic characteristics which is a basic relationship between the stroke amount of the brake pedal and the braking force. When the second mode is selected, the ECU executes an automatic braking force control when the stroke amount is between a first threshold value and the second threshold value after the stroke amount of the brake pedal increases and reaches a predetermined set value. The ECU executes normal control when the stroke amount of the brake pedal becomes larger than the second threshold value.