Pneumatic Brake Booster Modulation Point Calibration
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Solution Overview
Problem
The accuracy of the control point in a pneumatic brake booster calibration is heavily dependent on component tolerances of pressure sensors and brake boosters, leading to inaccuracies in the transition between pneumatic and hydraulic amplification.
Innovation Solution
A method that calculates the control point using the quotient of brake master cylinder pressure and pedal travel, identifying a local maximum in the gradient profile to correct the modulation point, thereby reducing sensor error robustness and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the control point is calculated using a linear equation with two parameters determined by calibration process, then the modulation point can be determined, but the accuracy is heavily dependent on component tolerances of pressure sensors and brake booster
Solution Approach 1:
The invention changes the calibration parameters from pressure difference-based parameters to parameters based on the quotient of master brake cylinder pressure and pedal travel. This parameter transformation makes the calibration independent of pressure sensor tolerances, as the quotient relationship compensates for sensor errors. The method determines a local maximum of the gradient profile of this quotient to identify the modulation point, thereby improving accuracy without being affected by component tolerances.
2Measurement precision
If the pressure difference between working chamber and vacuum chamber is increased until saturation point is exceeded, then the modulation point can be detected as minimum of pressure curve, but the process requires complex calibration procedure
Solution Approach 1:
The invention extracts the essential characteristic for modulation point detection from the complex pressure difference calibration process. Instead of requiring the full calibration procedure with pressure difference manipulation, the method uses the quotient of master brake cylinder pressure and pedal travel, whose gradient profile directly reveals the modulation point at its local maximum. This extraction simplifies the calibration while maintaining detection accuracy.
3Reliability
If the quotient of master brake cylinder pressure and pedal travel is used to determine control point, then robustness against sensor errors is improved, but additional measurements are required
Solution Approach 1:
The invention makes the pedal travel sensor serve multiple functions: it is used both for determining the quotient (which provides robustness against pressure sensor errors) and for identifying the modulation point through gradient analysis. The master brake cylinder pressure sensor similarly contributes to both the quotient calculation and the overall control system. This multi-functionality approach achieves sensor error robustness without requiring entirely separate measurement systems.
Data Source
Figure 1~2
Figure 3~4
AI summary
The invention relates to a method for calibrating a modulation point of a pneumatic brake booster (10) which is calculated from the at least one pressure sensor signal, in which method the vacuum pressure of a vacuum chamber and/or the working pressure of a working chamber of the brake booster (10) are/is determined by means of a pressure sensor (11) which generates the pressure sensor signal, and the vacuum chamber of the brake booster (10) can be operatively connected to a master brake cylinder (20) in order to generate a master brake cylinder pressure as a function of the pedal travel of a brake pedal (30); according to the invention the following method steps are provided: a) determination of the master brake cylinder pressure (pH) and of the pedal travel (sp), b) generation of the quotient (pH/sp) from the master brake cylinder pressure (pH) and pedal travel (sp), c) determination of a local maximum value (4) of the profile of the quotient (pH/sp) formed from the master cylinder pressure (pH) and the pedal travel (sp), d) determination of a further modulation point as that value of the master brake cylinder pressure (pH) which corresponds to the local maximum value (4) determined in method step c), and e) correction of the calculated modulation point by means of the further modulation point which is determined in method step d).