Electric Vehicle Deceleration Control During Battery Saturation
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Solution Overview
Problem
Electric vehicles face challenges when the battery is fully charged during coasting, as regenerative braking is limited, leading to potential collisions or undesirable temperature changes due to air conditioner or heater operation, and deteriorated drivability from fuel-cut control.
Innovation Solution
A deceleration control method and system that determines if the vehicle is coasting, compares coasting speed with a predetermined creep speed, calculates regenerative power generation, and generates a hydraulic pressure braking torque when the regenerative power exceeds the battery's chargeable power, using sensors and a deceleration control unit to manage regenerative and hydraulic pressure braking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If regenerative braking is used to collect inertial energy during coasting, then energy recovery is improved, but when the battery is fully charged, the regenerative power cannot charge the battery leading to collision risk
Solution Approach 1:
The patent introduces a deceleration control unit as an intermediary that manages the transition between regenerative braking and hydraulic pressure braking. When the battery is fully charged, this control unit activates hydraulic pressure braking to provide the necessary deceleration force, ensuring reliable collision prevention while regenerative braking continues to operate when battery charging is possible.
Solution Approach 2:
The system dynamically changes the braking mechanism based on battery charge state parameters. When battery SOC reaches 100%, the system switches from relying solely on regenerative braking to combining or replacing it with hydraulic pressure braking, thereby adapting to the changing energy storage capacity and maintaining reliable deceleration control.
2Speed
If fuel-cut control is used when battery is fully charged, then deceleration is achieved, but drivability rapidly deteriorates
Solution Approach 1:
The patent employs hydraulic pressure braking as an alternative to fuel-cut control when the battery is fully charged. The hydraulic brake system provides smooth and controllable deceleration force, maintaining comfortable drivability while achieving the necessary speed reduction, unlike the abrupt fuel-cut control method.
3Use of energy by moving object
If air conditioner or heater operates to consume regenerative power, then power utilization is improved, but temperature varies and drivability deteriorates
Solution Approach 1:
The deceleration control unit continuously monitors battery charge state and dynamically adjusts the braking strategy. When battery SOC is below 100%, regenerative braking is prioritized for energy recovery; when SOC reaches 100%, the system switches to hydraulic pressure braking. This feedback-based control ensures optimal power utilization without compromising cabin temperature stability or drivability.
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 safe and efficient deceleration by hydraulic pressure braking when the battery is fully charged, preventing collisions and maintaining drivability by utilizing hydraulic pressure braking when regenerative power exceeds battery capacity during coasting.
Implementation Method 1
The motor 20 of the hybrid electric vehicle and a motor of the pure electric vehicle generally operate as a generator for collecting inertial energy during the regenerative braking (RB) mode
Implementation Method 2
uses friction torque (negative torque) of the engine
Data Source
AI summary
A deceleration control method and system for an electric vehicle that performs deceleration by hydraulic pressure braking when a battery of the electric vehicle is in a fully charged state while coasting. The deceleration control method for an electric vehicle includes determining whether the electric vehicle is coasting, comparing a coasting speed with a predetermined creep speed when the electric vehicle is coasting, calculating an amount of regenerative power generation corresponding to the coasting speed when the coasting speed is higher than the predetermined creep speed, comparing the calculated regenerative power generation amount with a chargeable power amount of the battery, and generating predetermined hydraulic pressure braking torque when the calculated regenerative power generation amount is higher than the chargeable power amount of the battery.