Vehicle Hold Control Using Mode Switching and Brake Force Balancing
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Solution Overview
Problem
Vehicle hold functions in vehicles with adaptive cruise control often require higher brake fluid pressure than necessary for stopping, leading to unnatural vehicle behavior and motor operation noise, which can be unsettling for users.
Innovation Solution
A vehicle control system that calculates and adjusts brake fluid pressure to maintain the vehicle in a stopped state by determining the required brake force and drive force based on target drive force calculations, using a combination of engine and motor drive sources, and selectively switching between engine and electric vehicle traveling modes to optimize brake fluid pressure boosting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brake fluid pressure is boosted to enable vehicle hold function, then the vehicle can be held in stopped state, but unnatural vehicle behavior and motor operation noise occur
Solution Approach 1:
The control device performs preliminary actions by switching traveling modes before vehicle stop timing. When the engine traveling mode is selected before stop, the system prepares to boost brake fluid pressure. When EV traveling mode is selected, the system suppresses brake fluid pressure boosting. This preliminary mode selection prevents unnatural behavior and noise by anticipating the need for pressure boosting and adjusting drive source operation accordingly.
Solution Approach 2:
The system dynamically switches between engine traveling mode and EV traveling mode based on real-time conditions and predicted stop requirements. This dynamic adaptation allows the vehicle to optimize brake fluid pressure management by selecting the appropriate traveling mode that minimizes unnatural behavior and motor noise while maintaining the vehicle hold function.
2Force
If brake fluid pressure is boosted at vehicle stop timing, then stop hold brake force is achieved, but motor operation noise increases
Solution Approach 1:
The control device determines the traveling mode before vehicle stop timing to predict whether brake fluid pressure boosting will be needed. By switching to EV traveling mode in advance when possible, the system prepares to suppress pressure boosting, thereby reducing motor operation noise while still achieving the required stop hold brake force through appropriate pressure management.
Solution Approach 2:
The system substitutes mechanical brake pressure boosting with electric motor control by selecting EV traveling mode. When EV mode is selected before stop, the control device suppresses brake fluid pressure boosting and instead uses motor braking force to achieve the stop hold function, replacing the mechanical pressure boosting process with an electrical control solution that generates no motor noise.
3Reliability
If engine traveling mode is selected before vehicle stop, then brake fluid pressure can be boosted, but energy consumption increases
Solution Approach 1:
The system dynamically selects between engine and EV traveling modes based on predicted stop requirements and current vehicle conditions. This dynamic switching optimizes energy consumption by choosing EV mode (which consumes less energy for the vehicle hold function) when the motor can provide sufficient braking force, and only resorting to engine mode with pressure boosting when necessary.
Solution Approach 2:
The control device changes the operating parameters by selecting different traveling modes that have different energy consumption characteristics. EV traveling mode operates with lower energy consumption for maintaining stopped state compared to engine traveling mode with pressure boosting. The system adjusts this parameter (traveling mode) based on real-time conditions to minimize energy usage while ensuring reliable vehicle hold function.
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 reduces the feeling of strangeness caused by brake fluid pressure boosting, maintaining vehicle stability and user comfort by optimizing brake fluid pressure and drive force distribution, thereby enhancing the vehicle hold function.
Implementation Method 1
a motor as a drive source that is driven by electric power supplied from a battery
Implementation Method 2
The required brake force is used to control hydraulic brake
Data Source
AI summary
A vehicle control system includes a target drive force calculation unit, an arithmetic unit, a stop holding unit, a power-running-generative drive force calculation unit, and a traveling mode selection unit. The arithmetic unit calculates required drive force and required brake force based on target drive force calculated by the target drive force calculation unit. The arithmetic unit calculates the required drive force by setting the required brake force to stop hold brake force or greater if an engine traveling mode is selected at an immediately preceding timing by the traveling mode selection unit. The arithmetic unit calculates the required brake force by setting the required drive force to less than or equal to power-running-generative drive force calculated by the power-running-generative drive force calculation unit if an electric vehicle traveling mode is selected at the immediately preceding timing by the traveling mode selection unit.