Vehicle Braking Device Hysteresis Compensation Control
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Solution Overview
Problem
In vehicle braking devices, the differential pressure valve's hysteresis property causes uncomfortable brake operation feelings due to differences in wheel pressure when the brake pedal is pressed and released, leading to fluctuations that do not match the driver's intended braking force.
Innovation Solution
A braking device with a differential pressure valve and a pump that adjusts the master chamber pressure only after a first brake operation amount is reached, using two relationships to control the differential pressure: one for increasing and another for decreasing brake operation amounts, with a greater reduction gradient than increase gradient to manage the hysteresis effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the differential pressure valve is used to control wheel pressure, then the braking force can be regulated, but the hysteresis property of the valve causes uncomfortable pedal feedback and fluctuation in brake operation feeling
Solution Approach 1:
The system pre-stores two different differential pressure relationships (first relationship for increasing brake operation amount, second relationship for reducing brake operation amount) in advance. When the brake operation amount changes, the control unit immediately selects and applies the appropriate pre-defined relationship, avoiding the hysteresis effect by not relying on real-time valve response that causes uncomfortable pedal feedback.
Solution Approach 2:
The invention changes the control parameter approach by using different differential pressure relationships based on the direction of brake operation change. The control unit switches between the first relationship (when brake operation amount increases) and the second relationship (when brake operation amount reduces), thereby compensating for the hysteresis property of the differential pressure valve and ensuring consistent pedal feedback.
2Use of energy by moving object
If the wheel pressure is adjusted to maximize regenerative braking force, then energy recovery is improved, but the pedal feeling is influenced by fluctuations not dependent on brake operation
Solution Approach 1:
The control unit continuously monitors the brake operation amount and uses this feedback to determine which differential pressure relationship to apply. By comparing the current brake operation amount with previous values, the system selects the appropriate pre-stored relationship (first or second) to maintain consistent pedal feedback while optimizing regenerative braking force generation.
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 configuration suppresses the uncomfortable feeling caused by the differential pressure valve's hysteresis and maintains consistent pedal feedback, ensuring the braking force matches the driver's intention and reducing pressure fluctuations.
Implementation Method 1
the actual wheel pressure (actual differential pressure) generated by the differential pressure valve differs between when a brake pedal is being pressed and when the brake pedal is being returned, even when an indicated pressure to the differential pressure valve is constant, due to the property (hysteresis) of the differential pressure valve
Implementation Method 2
a pump that ejects brake fluid to a portion between the differential pressure valve and the wheel cylinder on the hydraulic pressure path
Implementation Method 3
a regenerative braking device that applies, to the wheel, a regenerative braking force obtained by converting a kinetic energy of the wheel to an electrical energy
Data Source
AI summary
A vehicle braking device includes a storage unit storing a first relationship between the brake operation amount and a first differential pressure when the brake operation amount is within a range less than a first brake operation amount and is increasing, and a second relationship between the brake operation amount and the first differential pressure when the brake operation amount is within a range less than the first brake operation amount and is decreasing. In the first relationship a relationship in which the first differential pressure increases as the brake operation amount increases, and in the second relationship a relationship in which the first differential pressure is reduced as the brake operation amount is reduced. The first differential pressure per unit reduction in the brake operation amount in the second relationship is greater than the first differential pressure per unit increase of the brake operation amount in the first relationship.