Brake-By-Wire Fallback Control for Wheel Speed Sensor Failure
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Solution Overview
Problem
Conventional brake-by-wire systems lose braking stability and control when a wheel speed sensor fails, leading to potential wheel lock and loss of steering capability.
Innovation Solution
A brake-by-wire system with a brake controller that outputs specific control signals to manage brake forces across four wheels, including stopping brake forces on one axle and adjusting brake forces on the other axle based on valid wheel speed signals, to maintain stable braking even with faulty wheel speed sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If wheel speed sensors are installed on all four wheels for independent slip ratio control, then wheel lock prevention capability is improved, but system reliability deteriorates when a sensor fails
Solution Approach 1:
The patent merges the braking control of wheels on the same axle by using a common brake force when one wheel speed sensor fails. Instead of completely disabling braking on the affected axle, the system combines control of both wheels on that axle under a single brake force command, allowing continued braking functionality while compensating for the missing sensor data.
Solution Approach 2:
The brake controller is designed to perform multiple functions: it can operate in normal mode with all four sensors, in degraded mode with one sensor failed using combined axle control, and in emergency mode with both sensors on an axle failed using cross-axle control. This multi-functionality ensures the system adapts to different failure scenarios while maintaining braking capability.
2Reliability
If wheel speed sensors are used for precise slip ratio control, then emergency braking safety is improved, but the vehicle becomes vulnerable to sensor failures
Solution Approach 1:
The system prepares for sensor failure by having pre-defined fallback control strategies. When a sensor failure is detected, the system automatically transitions to a degraded control mode where brake forces are adjusted based on available sensor data and vehicle dynamics models, cushioning the impact of the failure and preventing complete loss of braking stability.
Solution Approach 2:
The system continuously monitors wheel speed sensor signals and compares them against expected values based on vehicle dynamics. When inconsistencies indicate sensor failure, the feedback mechanism triggers a mode switch to degraded or emergency control strategies, maintaining braking stability despite the fault condition.
3Ease of operation
If independent brake force control is applied to each wheel, then wheel lock prevention is improved, but control complexity increases when sensors fail
Solution Approach 1:
The control system is segmented into independent operational modes that can be activated based on sensor availability. The controller divides the four-wheel braking system into manageable control groups (individual wheels when sensors are available, paired wheels on the same axle when one sensor fails, or cross-axle pairing when both sensors on an axle fail), simplifying control signal management in each mode.
Data Source
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AI summary
This application provides a brake-by-wire system for a vehicle, the vehicle, and a control method for the brake-by-wire system for the vehicle, relates to the field of new energy vehicles, and may be applied to an electric vehicle and a hybrid vehicle. A brake controller is communicatively connected to a wheel speed sensor of each wheel of the vehicle. The brake controller is configured to output a second control signal in response to invalidity of a wheel speed sensor of one wheel on one axle. The second control signal is used to control two brake units corresponding to the other axle to output brake forces and control two brake units corresponding to the one axle to stop outputting brake forces. Therefore, even if the wheel speed sensor of the wheel on the one axle is invalid, a wheel on the other axle can still be controlled, to prevent the wheel on the other axle from being locked. This can improve traveling safety of the vehicle.