Electric Booster Brake Pedal Detection via Relative Position Threshold
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Solution Overview
Problem
Conventional electric boosters face challenges in accurately detecting driver-operated brake pedal movements during automatic brake control due to the assist piston's advancement, which can pull the input piston and brake pedal inward, making it difficult to distinguish between automatic and driver-initiated brake operations.
Innovation Solution
An electric booster system that includes an input member, an assist member, a master cylinder, an electric actuator, a controller, and a biasing unit, which sets a determination threshold value for the relative position between the input and assist members, allowing the controller to determine if the brake pedal is operated by comparing the relative position with this threshold and detecting a predetermined movement of the input member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the assist piston is advanced during automatic brake control, then the brake hydraulic pressure is increased, but the input piston is pulled in toward the master cylinder through the neutral spring, causing false detection of brake pedal operation
Solution Approach 1:
The detection function is segmented into two independent parts: brake pedal operation detection (via stroke sensor detecting input piston displacement) and automatic brake control status detection (via controller monitoring assist piston position). This segmentation allows the system to distinguish between genuine brake pedal operations and input piston movements caused by assist piston advancement during automatic control.
Solution Approach 2:
The stroke sensor acts as an intermediary detection device that directly monitors input piston displacement independent of the assist piston's position. By introducing this separate detection mechanism, the system can accurately determine whether the driver has operated the brake pedal without being influenced by the neutral spring's pull-in effect during automatic brake control.
2Device complexity
If only brake pedal displacement is monitored, then the detection system remains simple, but it becomes difficult to distinguish between brake pedal displacement caused by assist piston advancement and displacement caused by actual driver operation
Solution Approach 1:
The controller receives feedback from both the stroke sensor (detecting input piston displacement) and the position sensor (detecting assist piston position). By processing this combined feedback information, the controller can reliably determine whether detected displacement results from driver operation or from automatic control assistance, thereby maintaining high detection accuracy.
Solution Approach 2:
The system replaces simple mechanical displacement monitoring with an integrated detection approach combining stroke sensor feedback and controller logic. This substitution transforms the detection mechanism from a purely mechanical system vulnerable to false signals into a智能化 control system that can interpret the meaning behind displacement events.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate detection of driver-operated brake pedal movements during automatic brake control, ensuring proper switching between automatic and driver-priority brake control modes, enhancing the system's reliability and accuracy.
Implementation Method 1
an electric actuator adapted to provide a thrust force to the assist member
Implementation Method 2
a biasing unit adapted to bias the input member and the assist member so that a relative position therebetween is moved toward a predetermined neutral position
Implementation Method 3
a master cylinder adapted to generate a brake hydraulic pressure according to a forward or backward movement of the assist member
Data Source
AI summary
An electric motor is controlled based on an operation of a brake pedal to move a primary piston forward through a ball screw mechanism, thereby generating a hydraulic pressure in a master cylinder. At this time, a reaction force from the hydraulic pressure in the master cylinder is fed back to the brake pedal through an input piston. Automatic brake control, which generates the hydraulic pressure by driving the electric motor regardless of whether there is the operation of the brake pedal, is carried out. During the automatic brake control, an actual relative position is compared with a determination threshold value set based on the relative position between the primary piston and the input piston which is generated by a movement of the primary piston, and it is determined that the brake pedal is operated in a case where the relative position is smaller than the determination threshold value.