Electromechanical Parking Brake Force Compensation After Actuator Failure
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Solution Overview
Problem
Existing braking systems with electromechanical brake actuators face challenges in safely holding a vehicle in various conditions, particularly when one or more actuators fail, especially on inclines or with heavy loads, due to varying brake pad and disc cooling and the need for precise control to prevent damage.
Innovation Solution
A braking system with individually controllable electromechanical brake actuators that includes a monitoring device to detect vehicle states and adjust braking force based on predetermined values and compensation values, ensuring safe holding by increasing braking force when necessary to compensate for faulty actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromechanical brake actuators are used for parking brake function, then emergency braking capability is enabled and service brake independence is improved, but control precision requirements increase and risk of excessive braking force exists
Solution Approach 1:
The control unit continuously monitors the actual braking force generated by the electromechanical brake actuator and compares it with the desired braking force. Based on this feedback, the control unit adjusts the actuator's operation in real-time to maintain precise control and prevent excessive braking force, thereby resolving the contradiction between enabling emergency braking and maintaining control precision.
Solution Approach 2:
The system dynamically adjusts the braking force by modifying the operational parameters of the electromechanical brake actuator based on real-time vehicle conditions, brake disc temperature, and actuator status. This dynamic control enables the system to adapt to changing conditions and maintain precise braking force control while providing emergency braking capability.
2Ease of operation
If fixed target braking force values are used for parking brake, then control simplicity is maintained, but insufficient braking force may occur when brake discs cool down
Solution Approach 1:
The control unit applies a preliminary compensation factor to the target braking force value before actuating the brake, anticipating the cooling effect on the brake disc. This preliminary adjustment ensures that sufficient braking force is available even as the brake disc cools down, while maintaining relatively simple control logic through predefined compensation strategies.
Solution Approach 2:
The system changes the target braking force parameter dynamically based on brake disc temperature and time since braking. By adjusting this parameter according to thermal conditions, the system ensures sufficient braking force is maintained throughout the cooling process while keeping the control approach straightforward through temperature-based parameter adjustment.
3Ease of operation
If brake actuators are controlled with predetermined braking force values, then control simplicity is maintained, but excessive wear occurs when actuators are faulty
Solution Approach 1:
The control unit continuously monitors the actual braking force and compares it with the commanded braking force. When a discrepancy is detected indicating a faulty actuator, the control unit adjusts the target braking force values for other actuators and reduces the faulty actuator's contribution to prevent excessive wear, while maintaining simple overall control through automated compensation.
Solution Approach 2:
The system implements a compensation mechanism that anticipates potential actuator failures by distributing braking force reserves across multiple actuators. When one actuator is identified as faulty, the previously reserved braking capacity of other actuators is activated to compensate, preventing the faulty actuator from operating in an excessive wear condition while maintaining simple control logic.
4Reliability
If monitoring device detects vehicle states and adjusts braking force dynamically, then braking safety is improved, but device complexity increases
Solution Approach 1:
The control unit is designed to perform multiple functions: it controls the electromechanical brake actuators for parking brake, monitors vehicle states through integrated sensors, detects actuator faults, calculates compensated target braking force values, and prevents excessive wear. By consolidating these diverse functions into a single multi-functional control unit, the system achieves improved braking safety while minimizing the increase in overall device complexity.
Data Source
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AI summary
The invention relates to a braking system (10) for performing a parking brake function (82) of a vehicle (100) with several individually controllable, in particular electromechanical, brake actuators (14), a monitoring arrangement (30) which is configured to detect at least a first state (38) and a second state (40) of the vehicle, and a brake control unit (20) which is configured to send a parking brake request signal (26) which preferably indicates a locking request (28a, 28b) of several or all wheels (12) of the vehicle (100).to receive and, after receiving the parking brake request signal (26), in the case of a first state (38) detected by the monitoring arrangement (30), to control each of the brake actuators with a predetermined value (48) as the target braking force value (22) for the respective brake actuator (14), and in the case of a second state (40) detected by the monitoring arrangement (30), to control at least one of the brake actuators (14) with a target braking force value (22) that corresponds to a sum (72) of the predetermined value (48) for one brake actuator (14) and a compensation value component (70) determined for one brake actuator (14). The invention further relates to a vehicle (100) with a brake system (10) and a method (200) for performing a parking brake function (82) of a brake system (10).