Hydraulic Valve Overflow Map for Brake Pressure Accuracy
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Solution Overview
Problem
Existing hydraulic or electrohydraulic vehicle brake systems face pressure position inaccuracies and control oscillations due to manufacturing tolerances, which are not adequately addressed by prior methods that only consider the control characteristic of valves, leading to suboptimal pressure regulation and increased costs from additional pressure sensors.
Innovation Solution
The method involves using an overflow characteristics map to account for additional valve characteristics beyond the control characteristic, allowing for precise pressure regulation by determining the pressure build-up and reduction speeds, and modifying the overflow map based on individual valve properties to improve accuracy without requiring individual measurement of each valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional pressure sensors are used in each wheel brake cylinder to achieve exact pressure measurement and adjustment, then pressure control precision is improved, but system cost increases
Solution Approach 1:
The patent creates a virtual copy of the pressure sensor function through software-based pressure estimation. Instead of using physical pressure sensors in each wheel brake cylinder, the system uses a pressure model that calculates expected pressure values based on valve characteristics and control signals. This virtual pressure measurement replaces the need for expensive additional hardware sensors while maintaining sufficient control precision.
Solution Approach 2:
The patent replaces the mechanical/physical pressure sensing system with an electronic/software-based pressure estimation system. The physical pressure sensors are substituted by a computational model that estimates pressure based on electrical signals to valves and known system characteristics, thereby reducing hardware complexity and cost.
2Device complexity
If only control characteristic is considered for valve calibration without additional pressure sensors, then device complexity is reduced, but pressure control precision deteriorates due to manufacturing tolerances
Solution Approach 1:
The patent implements a feedback mechanism where the pressure model continuously compares expected pressure values with actual system behavior. The valve characteristics are calibrated and stored, and the pressure model uses these calibrated values along with current valve control signals to estimate actual pressure. This feedback loop allows the system to compensate for manufacturing tolerances and maintain precision without additional sensors.
Solution Approach 2:
The patent changes the approach from directly measuring pressure to estimating pressure through parameter calculations. By using calibrated valve characteristics (control characteristic and overflow characteristic) and control signals as input parameters, the system computes pressure values through a pressure model, transforming the measurement problem into a calculation problem that is less sensitive to manufacturing variations.
3Device complexity
If manufacturing tolerances of valves and pumps are not compensated, then device complexity remains low, but pressure position accuracy deteriorates leading to control oscillations
Solution Approach 1:
The patent performs preliminary calibration of valve characteristics before normal operation. The control characteristic and overflow characteristic of each valve are determined and stored in advance. This preliminary characterization of components allows the pressure model to account for individual manufacturing variations, compensating for tolerances before they cause control problems during actual brake operation.
Solution Approach 2:
The system uses its own existing data (valve control signals and calibrated characteristics) to compensate for manufacturing tolerances. The pressure model leverages information already available in the control system to self-correct for component variations, eliminating the need for external calibration equipment or additional sensors during normal operation.
Data Source
Figure 1~3
AI summary
The invention relates to a method for optimizing the pressure setting accuracy. In said method, a hydraulic pressure is built up according to a pressure requirement by means of a hydraulic pump, and overflow control is performed using an analog-controlling hydraulic valve and a known control characteristic curve of the analog-controlling hydraulic valve, which overflow control counteracts a pressure build-up produced by the hydraulic pump that exceeds the pressure requirement. The method is characterized in that, in addition to the known control characteristic curve of the analog-controlling hydraulic valve, at least one additional valve characteristic is taken into account for the overflow control.