EV Wheel Holding Transition to Prevent Brake Creak and Vibration
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Solution Overview
Problem
Existing methods for holding electric vehicles at a standstill on inclined surfaces often result in uncomfortable noises and vibrations due to the transition from motor-based holding to service brake holding.
Innovation Solution
A method where the motor torque is gradually reduced at individual wheels while the service brake remains inactive, allowing the service brake to take over only after the motor torque has been completely reduced, thereby avoiding simultaneous activation and reducing noise and vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the service brake is activated simultaneously with the reduction of motor torque during holding transition, then the vehicle can be held safely at a standstill, but uncomfortable noises and vibrations occur for vehicle occupants
Solution Approach 1:
The holding transition is segmented into distinct phases: first reducing motor torque to zero, then activating the service brake. This segmentation prevents simultaneous operation of both systems, eliminating the creaking noises and vibrations that occur when they operate together during the transition.
Solution Approach 2:
The motor torque is reduced to zero before the service brake is activated. This preliminary action ensures that the electric drive motor is completely disengaged from the holding function before the mechanical brake takes over, preventing the harmful interactions that cause noise and vibration.
2Adaptability or versatility
If the motor torque is reduced while the service brake takes over simultaneously, then the transition from motor-based holding to brake-based holding can occur, but creaking noises and vibrations are generated
Solution Approach 1:
The holding function is maintained continuously throughout the transition by ensuring that either the motor torque or the service brake is actively holding the vehicle at any given moment. The service brake is activated only after motor torque reaches zero, ensuring continuous holding action without interruption or harmful simultaneous operation.
3Reliability
If the service brake is activated during motor torque reduction, then the holding function can be maintained, but the comfort for vehicle occupants deteriorates due to noise and vibration
Solution Approach 1:
The motor torque is reduced to zero as a preliminary step before activating the service brake. This ensures that the electric drive motor is completely disengaged before the mechanical brake engages, preventing the harmful interactions that cause noise and vibration while maintaining continuous holding function.
Data Source
AI summary
A method for holding a two-track motor vehicle. The motor vehicle has at least one electric drive machine. Four wheels of the motor vehicle can be held via a service brake. In an initial situation when the motor vehicle is at a standstill, the motor vehicle is held by virtue of a motor torque of the electric drive machine applied to at least two wheels. In a manner dependent on a situation and/or gradient, the motor torque that holds the at least two wheels is reduced at one wheel. After the motor torque at the one wheel is reduced, the service brake at the wheel is activated. After the service brake at the one wheel is activated, the motor torque at a further wheel is reduced. After the motor torque at the further wheel is reduced, the service brake at the further wheel is activated.