Brake Booster Zero Point Detection via Learning Operation
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Solution Overview
Problem
Existing electrically driven brake boosters face challenges in accurately detecting the zero point due to variations in temperature characteristics and sensor mount errors, leading to reduced control precision.
Innovation Solution
An electrically driven brake booster system that includes a master cylinder, a pressing member, an electrically driven actuator, and a controller, which uses a learning operation to detect the reference point by having a moving member contact a fixed member, allowing for precise control of hydraulic pressure and improving detection precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If sensor values are used directly for control, then the system is simple to operate, but detection precision deteriorates due to temperature characteristics and sensor variation
Solution Approach 1:
The system performs preliminary learning operations to establish reference values for sensor readings at specific positions (brake pedal not operated, brake pedal operated, master cylinder pressure zero). These pre-acquired reference values are stored and used for subsequent control operations, eliminating the need for complex real-time compensation algorithms while maintaining high detection precision.
2Measurement precision
If reference point detection is performed continuously, then detection precision is maintained, but loss of time increases due to frequent learning operations
Solution Approach 1:
The learning operation is performed periodically under specific conditions (when brake pedal is not operated and master cylinder pressure is zero) rather than continuously. This periodic execution maintains reference point accuracy while minimizing interference with normal braking operations and reducing overall time loss.
3Reliability
If learning operation is performed frequently, then reference point accuracy is maintained, but productivity decreases due to operational interruptions
Solution Approach 1:
The system proactively performs learning operations during idle periods when the brake pedal is not operated and master cylinder pressure is zero, before accuracy degradation occurs. This preliminary action ensures reference point accuracy is maintained without requiring frequent interruptions during active braking, thus preserving both reliability and productivity.
Data Source
AI summary
In an electrically driven brake booster wherein an electrically driven actuator moves a booster piston upon operation of a brake pedal to generate a hydraulic pressure for driving a brake force at the maser cylinder, the electrically driven actuator controls to move the booster piston as the pressing member in order to correctly detect presence/absence of an operation of the booster piston and detect a movement pattern of an input rot and an input piston as the shaft member relative to a movement of the pressing member. In accordance with the movement pattern, presence/absence of an operation of the brake pedal is detected. By confirming that the brake pedal is not operated, by the method described above, a zero point of a stroke sensor for detecting the position of the shaft member and zero points of oil pressure sensors for detecting a hydraulic pressure supplied by the master cylinder are learnt.