Regenerative Braking Threshold Switching for Electric Vehicles
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Solution Overview
Problem
Existing electric vehicle technologies fail to generate braking force when frictional braking is limited, particularly due to battery full charge or temperature issues, leading to inadequate braking performance.
Innovation Solution
An electrically powered vehicle system that includes a regenerative braking force generator, a frictional braking force generator, and a controller that adjusts regeneration limit threshold values to ensure continuous braking force generation, switching between regenerative and frictional braking based on driver demand and vehicle state, even when frictional braking is limited.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If regenerative braking force is limited due to battery full charge or temperature issues, then braking force generation is insufficient, but switching to frictional braking force alone cannot provide adequate braking performance when frictional braking is also limited
Solution Approach 1:
The patent implements dynamic switching between two regenerative braking force limit threshold values (first and second thresholds) based on vehicle operating conditions. The controller selectively applies a higher second threshold when frictional braking is limited to maximize regenerative braking contribution, while using a lower first threshold under normal conditions. This dynamic adjustment optimizes the braking force distribution and ensures reliable braking performance across varying operational scenarios.
Solution Approach 2:
The patent changes the parameter of regenerative braking force limit threshold value based on the availability of frictional braking force. When frictional braking is determined to be limited (due to temperature or other constraints), the system switches from the first threshold value to the second threshold value, thereby increasing the maximum allowable regenerative braking force. This parameter change enables the system to adapt to different braking capability conditions and maintain reliable braking performance.
2Reliability
If the system switches from first regeneration limit threshold value to second regeneration limit threshold value to enable braking force generation, then braking performance is improved, but sudden switching may cause driver surprise or discomfort
Solution Approach 1:
The patent determines in advance whether frictional braking is limited and proactively switches to the appropriate regenerative braking force limit threshold value before braking force deficiency occurs. By assessing the frictional braking capability ahead of time and pre-adjusting the regenerative braking threshold, the system prevents sudden loss of braking force and ensures smooth, predictable braking behavior from the driver's perspective.
Solution Approach 2:
The system continuously monitors the operational status of frictional braking (temperature, availability) and uses this feedback to dynamically adjust the regenerative braking force limit threshold. This closed-loop feedback mechanism ensures that the threshold switching is based on real-time system conditions, optimizing braking performance while maintaining smooth transitions that prevent driver surprise.
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
Enables consistent braking force generation under regeneration limiting conditions, preventing sudden loss of braking force and improving driver experience by smoothing transitions and maintaining braking performance.
Implementation Method 1
a regenerative braking force generator that generates regenerative braking force in a vehicle
Implementation Method 2
a battery that stores electrical power regenerated with the regenerative braking force
Implementation Method 3
a frictional braking force generator that generates frictional braking force in a vehicle
Data Source
AI summary
A MG-ECU includes, as a regeneration limiting value, a limited value set according to a state of a battery, and an unlimited value enabling generation of braking force greater than the limited value. In a state in which regenerative braking is being limited, the MG-ECU causes frictional braking force to be generated based on a difference between the unlimited value and the drive force demand of a driver. In cases in which the frictional braking force is also limited in a state of the regenerative braking, the MG-ECU switches the regeneration limiting value from the limited value to the unlimited value, and requests a motor-generator to generate regenerative braking based on the limited value.