Electric Brake Re-Clamping Sequence for Fail-Open Parking Hold
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Solution Overview
Problem
The electric brake apparatus with a fail-open mechanism experiences a decline in performance when a failure occurs during re-clamping, leading to a loss of braking force, especially when voltage drops or power supply disruptions occur, affecting the ability to keep a vehicle stopped.
Innovation Solution
The electric brake apparatus desynchronizes re-clamping between the left and right wheels by not releasing the holding of braking force on one wheel until re-holding control is completed on the other wheel, ensuring that braking force is maintained on at least one wheel even if a failure occurs during re-clamping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If re-clamping is performed on both left and right wheels simultaneously, then the braking force can be restored quickly after thermal contraction, but a voltage drop or power supply disruption during re-clamping causes both wheels to lose braking force, declining the performance of keeping the vehicle stopped
Solution Approach 1:
The re-clamping operation is divided into separate sequential steps for left and right wheels instead of being performed simultaneously. The controller performs re-clamping on one wheel first, completes it, then performs re-clamping on the other wheel. This segmentation ensures that if a power failure occurs during re-clamping of one wheel, the other wheel maintains its braking force, preventing complete loss of stopping capability.
Solution Approach 2:
The controller performs re-clamping on one wheel before releasing the braking force holding on the other wheel. This preliminary action ensures that at least one wheel maintains reliable braking force throughout the re-clamping process, serving as a safety backup during the operation.
2Adaptability or versatility
If the electric brake apparatus operates with a fail-open mechanism, then the system can continue operating after motor failure, but the braking force is completely released when a voltage drop occurs during re-clamping, affecting vehicle stopping performance
Solution Approach 1:
The sequential re-clamping approach segments the vulnerable operation into isolated steps. By completing re-clamping on one wheel before releasing the hold on the other, the system ensures that partial failure during the process does not result in complete loss of braking capability, improving reliability while maintaining fail-open adaptability.
Solution Approach 2:
The braking force holding mechanism on one wheel serves as a cushioning backup during the re-clamping operation on the other wheel. This beforehand cushioning ensures that even if re-clamping fails due to voltage drop, the vehicle stopping performance is maintained by the other wheel's held braking force.
3Productivity
If re-holding control is performed on both wheels at the same time, then the overall braking force restoration is faster, but the complexity of control increases and the risk of simultaneous failure increases
Solution Approach 1:
The control process is segmented into sequential phases for left and right wheels. This segmentation reduces control complexity by eliminating the need for complex synchronization logic while still achieving efficient braking force restoration through the ordered sequence of operations.
Data Source
AI summary
An electric brake apparatus includes a brake mechanism, a parking mechanism, and a main ECU and rear electric brake ECUs. The main ECU performs re-holding control (re-clamping) of, after holding a braking force by the parking mechanism, releasing the holding of the braking force with the braking force applied or maintained and further applying the braking force, and then holding the braking force by the parking mechanism after that. In this case, the main ECU does not release the braking force on a rear right wheel until completing the re-holding control on a rear left wheel side. Alternatively, the main ECU does not release the braking force on the rear left wheel side until completing the re-holding control on the rear right wheel.