Vehicle Braking Control via Slip Rate Mediation
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Solution Overview
Problem
Hybrid and electric vehicles face instability in braking due to rapid changes in brake hydraulic pressure and residual regenerative braking force, which can lead to slippage and fluctuation, compromising braking stability, especially during the transition between regenerative and hydraulic braking modes.
Innovation Solution
A vehicle braking system that detects wheel velocities and calculates slip amounts and change rates to control regenerative braking force, minimizing the switch section between regenerative and hydraulic braking by using pre-stored regenerative braking forces based on exceeding slip amounts and change rates, and operates safety functions like ABS or ESC to secure braking stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If regenerative braking force is used during safety function operation, then energy recovery is improved, but braking stability deteriorates due to slippage and fluctuation
Solution Approach 1:
The patent introduces slip amount and slip change rate as intermediary parameters to mediate between regenerative braking force and hydraulic braking force. By calculating the slip amount (difference between wheel velocity and vehicle velocity) and slip change rate, the system determines the appropriate regenerative braking force to apply, preventing excessive slip that would cause instability while maximizing energy recovery. This intermediary control mechanism resolves the contradiction by providing a buffer between the two braking forces.
Solution Approach 2:
The patent changes the control parameters from direct braking force control to slip-based control. By using slip amount and slip change rate as control parameters, the system dynamically adjusts regenerative braking force based on actual wheel slip conditions. This parameter change allows the system to maintain braking stability while recovering energy, as the slip parameters provide real-time feedback on the effectiveness of regenerative braking and when hydraulic braking should be applied.
2Force
If regenerative braking and hydraulic braking are used simultaneously, then braking force is improved, but braking stability deteriorates due to switch section fluctuations
Solution Approach 1:
The patent implements dynamic control of the braking system by continuously monitoring slip amount and slip change rate, and dynamically adjusting the ratio of regenerative braking force to hydraulic braking force. Rather than using fixed braking force distribution, the system adapts in real-time based on wheel slip conditions, ensuring smooth transitions between braking modes and eliminating the stability issues caused by rigid switch sections.
Solution Approach 2:
The patent employs feedback control by using slip amount and slip change rate as feedback parameters to continuously adjust braking force distribution. The slip amount provides feedback on the current state of wheel slip, and the slip change rate provides feedback on the rate of change of slip. This dual feedback mechanism allows the system to maintain optimal braking force distribution and stability during transitions between regenerative and hydraulic braking.
3Reliability
If ABS or ESC safety function is operated during regenerative braking, then vehicle safety is improved, but regenerative braking efficiency deteriorates due to rapid hydraulic pressure changes
Solution Approach 1:
The patent applies preliminary action by calculating and determining the appropriate regenerative braking force before ABS or ESC safety functions are activated. By using slip amount and slip change rate to pre-determine the regenerative braking force level, the system prepares the braking configuration in advance, allowing for smoother transitions when safety functions are activated and minimizing the negative impact on regenerative braking efficiency.
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 effectively restricts regenerative braking force using slip amounts and change rates, minimizing the transition between braking modes and enhancing braking stability by ensuring stable hydraulic braking, thus maintaining vehicle stability during safety function operations.
Implementation Method 1
a wheel velocity detection unit detecting velocities of respective wheels provided at a vehicle
Implementation Method 2
calculating slip amounts of the respective wheels by comparing the vehicle velocity and the velocities of the respective wheels
Implementation Method 3
the motor performs the function of an electric generator if a driver gives a decelerating command or a braking command, and thus generates electric energy
Implementation Method 4
hydraulic braking force using brake hydraulic pressure
Data Source
AI summary
Disclosed herein is a vehicle braking system and control method. The vehicle braking control method includes detecting velocities of respective wheels provided at a vehicle, calculating a vehicle velocity based on the velocities of the respective wheels, calculating slip amounts of the respective wheels by comparing the vehicle velocity and the velocities of the respective wheels, calculating change rates of the slip amounts of the respective wheels, obtaining regenerative braking force corresponding to one of the slip amounts and the slip change rates of the respective wheels, and controlling regenerative braking using the obtained regenerative braking force.