Electromechanical Parking Brake Dynamic Control
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Solution Overview
Problem
Existing brake systems for motor vehicles face challenges in maintaining safety and stability during braking, especially when the hydraulic service brake device is partially failed or operating in an unboosted mode, and they lack effective control over braking forces without relying on wheel speed measurements.
Innovation Solution
A method that simultaneously engages the hydraulic service brake on the front axle and the electromechanical parking brake on the rear axle, regulating the actual longitudinal deceleration of the vehicle to a target deceleration by controlling the electromechanical actuators based on brake pressure and transverse acceleration, allowing for an improved braking effect without relying on wheel speed information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the hydraulic service brake device is partially failed or operating in unboosted mode, then braking safety is compromised, but the system cannot provide sufficient braking force
Solution Approach 1:
The braking system is divided into two independent segments: the hydraulic service brake device for the front axle and the electromechanical parking brake device for the rear axle. This segmentation allows the rear brake system to independently provide braking force when the hydraulic system is compromised, ensuring braking safety is maintained even when one segment fails or operates in reduced capacity.
Solution Approach 2:
The control unit acts as an intermediary that coordinates between the degraded hydraulic service brake system and the electromechanical parking brake system. It calculates the required braking force distribution and activates the parking brake actuators to supplement insufficient hydraulic braking force, thereby maintaining overall braking safety and effectiveness.
2Force
If the electromechanical parking brakes are used for dynamic braking, then braking force is achieved, but vehicle stability is compromised due to uncontrolled braking forces
Solution Approach 1:
The control unit continuously monitors the actual longitudinal deceleration of the vehicle and compares it with the target deceleration value. Based on this feedback, it dynamically adjusts the braking force applied by the electromechanical parking brake actuators, ensuring that the braking force is precisely controlled to maintain vehicle stability while achieving the desired deceleration.
Solution Approach 2:
The braking system transitions from static, binary control (brake applied or not) to dynamic, continuous control. The control unit continuously modulates the braking force of the electromechanical parking brakes based on real-time vehicle deceleration requirements, enabling smooth and stable braking performance that adapts to changing driving conditions.
3Extent of automation
If the EPB control button is pressed to activate dynamic braking, then braking is initiated, but the application forces cannot be metered in an analogue way
Solution Approach 1:
The manual, binary control mechanism of the EPB control button is replaced with an automated electronic control system. The control unit receives the driver's braking request through the button press and automatically calculates, modulates, and applies the appropriate braking force through the electromechanical parking brake actuators, eliminating the need for manual force metering while maintaining ease of operation.
4Measurement precision
If wheel speed measurements are used for brake control, then precise braking control is achieved, but the system fails when wheel speed sensors are unavailable or fail
Solution Approach 1:
The braking control system extracts its dependency from wheel speed sensors and instead uses vehicle longitudinal deceleration measurements. By removing the requirement for wheel speed measurement, the system maintains precise braking control capability while becoming immune to wheel speed sensor failures or unavailability, significantly improving system reliability.
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
This approach enhances braking safety and stability by ensuring proportional braking forces between the front and rear axles, maintaining vehicle control and preventing wheel locking, even in conditions where wheel speed sensors are unavailable or fail.
Implementation Method 1
a parking brake device with wheel brakes on a rear axle that can each be actuated by an electromechanical actuator
Implementation Method 2
a hydraulic service brake device with hydraulically actuable wheel brakes on at least one front axle
Implementation Method 3
An actual longitudinal deceleration of the motor vehicle is measured
Data Source
Figure 1
AI summary
The invention relates to a method for operating a brake system of a motor vehicle having a hydraulic service brake device (10) having hydraulically actuatable wheel brakes (1, 2) on at least a front axle (VA) of the motor vehicle and having a parking brake device (20) having wheel brakes (5, 6) actuatable by respective electromechanical actuators on a rear axle (HA) of the motor vehicle, wherein a motor-vehicle actual longitudinal deceleration (aFzg,ist) is measured, wherein, during braking by means of the hydraulic service brake device (10) during travel of the motor vehicle, braking is performed by means of the parking brake device (20), wherein a motor-vehicle target longitudinal deceleration (aFzg,soll) to be achieved is determined and the electromechanical actuators of the parking brake device (20) are controlled in such a way that the motor-vehicle actual longitudinal deceleration (aFzg,ist) is controlled to the motor-vehicle target longitudinal deceleration (aFzg,soll). The invention further relates to a brake system.