Vehicle Brake Pressure Control with Variable Gradient Release
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Solution Overview
Problem
Conventional vehicle brake hydraulic pressure control systems experience variability in driver feedback during pressure hold control cancellation, depending on the magnitude of brake hydraulic pressure held, leading to sensations like dragging or sudden starting.
Innovation Solution
A vehicle brake hydraulic pressure control apparatus employing an initial rapid pressure reduction mode followed by a latter normal pressure reduction mode, with the switching threshold adjusted based on accelerator opening and road surface gradient, to ensure consistent and smooth pressure release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the brake hydraulic pressure is reduced by a constant gradient, then the pressure reduction is simple to control, but the feeling at cancellation varies depending on the magnitude of held pressure (dragging sensation)
Solution Approach 1:
The patent applies dynamics by making the pressure reduction rate variable rather than constant. The control system dynamically adjusts the pressure reduction gradient based on the held pressure magnitude: using a first gradient for high held pressure and a second gradient for low held pressure. This dynamic adjustment ensures consistent driver feedback regardless of the initial held pressure level, resolving the contradiction between simple control and reliable feedback.
Solution Approach 2:
The patent changes the parameter of pressure reduction gradient based on the held pressure magnitude. When held pressure is high, a first (steeper) gradient is applied; when held pressure is low, a second (gentler) gradient is applied. This parameter change approach allows the system to maintain consistent driver feedback across different operating conditions while keeping the control logic relatively simple.
2Productivity
If the brake hydraulic pressure is reduced by a steeper gradient when high pressure is held, then the pressure reduction is faster, but the feeling at cancellation is deteriorated (sudden starting sensation)
Solution Approach 1:
The system dynamically selects the appropriate pressure reduction gradient based on the held pressure magnitude. For high held pressure, a steeper first gradient is used to achieve faster reduction. For low held pressure, a gentler second gradient is used to avoid sudden starting sensation. This dynamic selection resolves the contradiction between fast reduction and smooth driver feedback.
Solution Approach 2:
The pressure reduction gradient parameter is changed based on the held pressure condition. The control system switches between two gradient values: a steeper gradient for high pressure conditions (improving productivity) and a gentler gradient for low pressure conditions (maintaining feedback consistency). This parameter adaptation resolves the contradiction between speed and smoothness.
3Reliability
If the brake hydraulic pressure is reduced at a normal gradient, then the driver feedback is smooth, but the pressure reduction takes longer when high pressure is held
Solution Approach 1:
The control system dynamically adjusts the pressure reduction rate based on the held pressure magnitude. When high pressure is held, a steeper first gradient is applied to reduce pressure quickly, minimizing time loss. When low pressure is held, a gentler second gradient is applied to maintain smooth driver feedback. This dynamic adjustment resolves the contradiction between reduction speed and feedback smoothness.
Solution Approach 2:
The pressure reduction gradient parameter is adaptively changed based on the held pressure condition. For high held pressure, a steeper gradient parameter is selected to reduce reduction time. For low held pressure, a gentler gradient parameter is selected to maintain feedback consistency. This parameter adaptation resolves the time-smoothness contradiction.
Data Source
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Figure 3A~3B
AI summary
One embodiment provides a vehicle brake hydraulic pressure control apparatus configured to perform a pressure hold control to hold a brake hydraulic pressure in a state in which a vehicle comes to a halt. Further, the pressure hold control is canceled using an initial pressure reduction mode in which the brake hydraulic pressure is reduced at one of a rapid pressure reduction rate of a previously-set given gradient and a normal pressure reduction rate calculated based at least on an accelerator opening, which is higher and a latter pressure reduction mode in which the brake hydraulic pressure is reduced at the normal pressure reduction rate after the brake hydraulic pressure has been reduced to a switching threshold by the initial pressure reduction mode.