Electromechanical Brake Auto-Hold Torque Coordination on Slopes
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Solution Overview
Problem
Electric vehicles equipped with electromechanical brake systems face issues with energy waste, drive motor fatigue, and smooth transition challenges when implementing automatic holding functions, particularly due to inefficient torque management and reliance on drive torque for stationary retention.
Innovation Solution
A control method for automatic holding that utilizes two brake control modules to continuously apply a sum of effective and margin brake torque, estimating road slope and vehicle mass to determine optimal torque levels, and adjusts drive torque output based on driver requests to minimize energy consumption and prevent slipping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electromechanical brake system outputs maximum parking braking force to implement automatic holding regardless of road slope, then the vehicle can be reliably held stationary, but energy is wasted
Solution Approach 1:
The brake control module dynamically adjusts the brake torque based on real-time road slope detection and vehicle state monitoring. The system transitions from static maximum braking force to dynamic adaptive braking force, matching the actual holding requirement while minimizing energy consumption.
Solution Approach 2:
The system changes the brake torque parameter from a fixed maximum value to a variable value that adapts to road slope conditions. By detecting road slope and calculating the required holding torque, the system optimizes the brake torque parameter to maintain reliability while reducing energy waste.
2Reliability
If the drive system outputs drive torque to hold the vehicle stationary, then the vehicle can be held on slopes, but the drive motor experiences fatigue and may be damaged
Solution Approach 1:
The system extracts the automatic holding function from the drive motor and assigns it to the electromechanical brake system. By separating these functions, the drive motor is relieved of the continuous torque output required for holding, thereby extending its service life while maintaining holding capability through the brake system.
Solution Approach 2:
The brake control module acts as an intermediary that manages the holding function independently from the drive motor. It detects vehicle state and road conditions, then controls the brake system to provide holding torque without requiring drive motor engagement, thus protecting the drive motor from fatigue.
3Use of energy by moving object
If the brake torque output by the electromechanical brake system is sufficient to keep the vehicle still, then energy is saved, but the switching process between brake torque and drive torque is not smooth enough causing vehicle flee or slip
Solution Approach 1:
The system performs preliminary detection of driver intent through accelerator pedal position and rate of change before switching from brake torque to drive torque. By anticipating the driver's action, the system can prepare for a smooth transition and avoid abrupt changes that would cause vehicle flee or slip.
Solution Approach 2:
The system continuously monitors vehicle state, accelerator pedal input, and torque requirements to determine the optimal switching point between brake and drive torque. This feedback mechanism ensures smooth transitions by adjusting the switching timing and torque transfer rate based on real-time conditions.
Data Source
AI summary
The present invention provides a control method for automatic holding, a vehicle's brake system and a brake control module thereof. The vehicle's brake system comprises two brake control modules and electromechanical brakes controlled by the brake control modules, a drive motor and a drive motor controller for controlling the drive motor. The control method comprises: after the vehicle transitions from moving to stationary, controlling the electromechanical brakes to continuously provide a brake torque, wherein the brake torque is a sum of the effective brake torque and a margin brake torque; and continuously outputting a drive-off signal to the drive motor controller to control the drive motor not to provide drive torque; until a driver requested drive torque is continuously increased to a critical torque which is close to the effective brake torque.