Electronic Park Brake Controller for Shift-by-Wire Transmission
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Solution Overview
Problem
In shift-by-wire transmission systems, the mechanical park brake function may fail to maintain vehicle stationary when the engine is off or electrical components are unpowered, due to potential failures in downstream torque transmission components, which can lead to unintended vehicle movement.
Innovation Solution
A controller is programmed to apply the electronic park brake when a speed difference between measured and expected speeds of downstream components exceeds a calibratable threshold, and the ignition is off, ensuring the vehicle remains stationary by engaging the electronic park brake independently of engine or electrical power states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical park brake system is used in shift-by-wire transmission, then the transmission can be locked to prevent vehicle movement, but the system may fail to maintain vehicle stationary when the engine is off or electrical components are unpowered
Solution Approach 1:
The electronic park brake is proactively applied based on predicted failure conditions (ignition off state, downstream component failures) before actual vehicle movement occurs. The controller monitors sensor inputs and applies the EPB in advance when failure modes are detected, preventing the need for mechanical park brake intervention.
Solution Approach 2:
The electronic park brake acts as an intermediary between the transmission mechanical park system and the vehicle braking system. It provides an additional layer of protection by independently engaging the wheel brakes when the mechanical park system may fail, without requiring direct modification to the mechanical park brake components.
2Reliability
If the electronic park brake is applied independently of engine or electrical power states, then the vehicle remains stationary even when unattended, but the system requires monitoring of multiple parameters and conditions
Solution Approach 1:
The controller leverages existing sensors and systems already present in the vehicle (speed sensors, ignition state monitoring, downstream component sensors) to detect failure conditions. Rather than adding dedicated monitoring systems, the electronic park brake controller utilizes multi-functional existing components to determine when EPB application is necessary.
Solution Approach 2:
The system continuously monitors sensor inputs (vehicle speed, downstream component speeds, ignition state) and provides feedback to the controller. When sensor readings indicate failure conditions (e.g., non-zero speed when vehicle should be stationary, ignition off state), the controller responds by applying the electronic park brake to maintain vehicle stationary status.
Data Source
AI summary
A vehicle includes a transmission mechanical park system, an electronic park brake, and at least one controller. The at least one controller is programmed to in response to (i) a speed difference of a measured speed and an expected speed of a downstream component of the vehicle that transmits torque downstream of the transmission mechanical park system exceeding a calibratable threshold and (ii) an ignition state of OFF, apply the electronic park brake to restrain movement of the vehicle.