Brake-by-wire fallback mode using pedal switch signals
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Solution Overview
Problem
Brake-by-wire systems face challenges in maintaining effective braking when there is a loss or degradation of signal from sensors, leading to potential inability to determine driver's braking demands, which can necessitate a transition to a mechanical hydraulic fallback mode, resulting in inadequate braking forces and feedback.
Innovation Solution
Implementing a by-wire fallback braking mode that uses a controller to command predetermined magnitudes of brake force based on the status of a brake pedal on/off switch, allowing the system to remain in a by-wire mode even with signal loss, thereby avoiding the need for a complete mechanical push-through fallback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical push-through system is activated as fallback when sensor signal is lost, then braking function can be maintained, but braking force magnitude and pedal feedback quality deteriorate
Solution Approach 1:
The system changes the operational parameters of the brake actuator to command predetermined magnitudes of brake force based on brake pedal position requests, even when sensor signals are lost. This allows the system to maintain reliable braking function while preserving adequate braking force magnitude through parameter-based control rather than mechanical push-through.
2Reliability
If a mechanical push-through system is activated as fallback, then braking can continue, but system complexity increases due to additional mechanical components
Solution Approach 1:
The patent replaces the mechanical push-through system with an electronic control-based fallback mechanism. The brake actuator is controlled electronically to provide predetermined magnitudes of brake force when sensor signals are lost, eliminating the need for complex mechanical push-through components while maintaining braking reliability.
3Reliability
If sensor signal loss occurs, then system reliability is compromised, but maintaining by-wire mode with predetermined brake force can preserve reliability while improving ease of operation
Solution Approach 1:
The system provides self-service during sensor signal loss by automatically commanding predetermined magnitudes of brake force based on brake pedal position requests without requiring driver intervention or system mode switching. The brake actuator autonomously maintains reliable braking function while preserving ease of operation.
Data Source
AI summary
A vehicle includes a brake-by-wire system that delivers a certain amount of brake fluid pressure to wheel brakes depending upon the position of a brake pedal. A brake-by-wire fallback or backup mode of operation is also provided. When activated, this by-wire fallback mode commands a certain, known magnitude of brake pressure. The commanded amount of brake pressure can vary based on the state of a brake pedal on/off switch, and can be set regardless of brake pedal position. This provides a backup to the brake-by-wire system without necessarily requiring a mechanical push-through backup system to brake the vehicle in the event a backup mode is required.