Wheel Brake Inlet Valve Current Switching for Quiet Pressure Control
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Solution Overview
Problem
Modern hydraulic motor vehicle braking systems face pressure control errors and high noise levels due to parameter and model inaccuracies when attempting to individually control inlet valves for wheel-specific brake pressures, especially in open-loop control functions.
Innovation Solution
A method involving an opening current applied to the inlet valve below its characteristic curve to ensure precise control, followed by a switch to an intermediate current for stable pressure setting, allowing for continuous pressure equalization without pulsing, thereby reducing noise emissions and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the inlet valve is actuated with pulsed current to individually control wheel brake pressures, then wheel-specific pressure control is achieved, but pressure control errors occur due to parameter and model inaccuracies
Solution Approach 1:
The patent implements feedback control by continuously monitoring the actual wheel brake pressure and comparing it with the target pressure. Based on the pressure difference, the control unit adjusts the actuating current to the inlet valve in real-time, correcting deviations caused by parameter inaccuracies and model errors. This closed-loop feedback mechanism ensures reliable pressure control despite initial inaccuracies in the control model.
2Speed
If the inlet valve is opened with high current to quickly build up brake pressure, then pressure build-up speed is improved, but noise emissions increase significantly
Solution Approach 1:
The patent employs periodic pulsed actuation of the inlet valve instead of continuous high current application. The control unit sends periodic opening commands to the inlet valve at optimized intervals, allowing pressure to build up in controlled pulses. This periodic action reduces the average noise level compared to continuous high-current operation while maintaining adequate pressure build-up speed for braking requirements.
3Loss of time
If the inlet valve is kept fully open to allow rapid pressure equalization, then pressure response time is reduced, but noise load and pressure control accuracy deteriorate
Solution Approach 1:
The patent dynamically adjusts the inlet valve opening degree based on real-time pressure conditions. Instead of keeping the valve fully open, the control unit modulates the valve opening proportionally to the pressure difference between system pressure and wheel brake pressure. This dynamic control allows rapid pressure equalization when needed while reducing valve opening (and associated noise) when pressure differences are small, thus resolving the contradiction between response time and noise reduction.
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
This approach enables precise and quiet control of wheel pressures by minimizing noise and reducing pressure control errors, even in the absence of direct pressure sensors, by using a pressure model to calculate actual wheel pressures and adjusting the valve current based on system and setpoint pressures.
Implementation Method 1
an electromagnetic actuator, in particular a solenoid, is assigned to the inlet valve
Data Source
AI summary
The disclosure relates to a method for controlling a hydraulic pressure in at least one wheel brake of a hydraulic motor vehicle braking system, wherein a system pressure is generated by an electrical pressure supply device and, by control of an in particular normally open inlet valve, having an opening current characteristic curve, a required hydraulic pressure, which is lower than the system pressure, is set in the at least one wheel brake. In order to improve the pressure control, provision is made that the inlet valve is opened by application of an opening current, in particular below the opening current characteristic curve, and is switched over from the opening current to an intermediate current on the opening current characteristic curve.