Brake System Pressure Estimation Using Actuator Torque
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Solution Overview
Problem
Existing brake-by-wire systems lack a reliable method for setting and adjusting the desired pressure in the pressure supplying device, especially when the pressure sensor fails or exceeds its measuring range, leading to inaccurate control of the brake pressure.
Innovation Solution
A method that determines pressure in a cylinder-piston arrangement using electromechanical actuator variables, such as actuator torque and position, through a pressure model, allowing for reliable setting and adjustment of the desired pressure, even without a functional pressure sensor, by integrating this information into an open-loop or closed-loop control unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure sensor is used to measure the brake pressure, then the pressure control accuracy is improved, but the system reliability deteriorates when the pressure sensor fails or exceeds its measuring range
Solution Approach 1:
The patent introduces an intermediary estimation method that uses actuator variables (torque, position) as mediators to infer pressure when the direct measurement via pressure sensor is unavailable or unreliable. This intermediary approach bridges the gap between actuator control and pressure outcome, maintaining system reliability during sensor failure.
Solution Approach 2:
The patent changes the measurement parameters from direct pressure sensing to indirect parameter estimation using actuator torque and position. By switching to these alternative parameters that remain available during sensor failure, the system maintains operational reliability while sacrificing some measurement precision under normal conditions.
2Reliability
If additional sensors are added to monitor pressure reliably, then the system reliability is improved, but the device complexity increases
Solution Approach 1:
The patent applies self-service by utilizing the existing actuator's own variables (torque, position) to monitor and estimate the pressure state. Instead of adding external sensors, the system uses the actuator's inherent data to serve the pressure monitoring function, avoiding additional hardware complexity.
Solution Approach 2:
The actuator serves multiple functions: it controls pressure generation and simultaneously provides data for pressure estimation. By making the actuator multi-functional, the system eliminates the need for separate dedicated pressure sensors, reducing overall device complexity while maintaining reliability.
3Reliability
If a pressure model is used to estimate pressure from actuator variables, then the system reliability under sensor failure is improved, but the manufacturing precision of pressure control deteriorates
Solution Approach 1:
The patent applies partial action by using the pressure model estimation only when necessary (during sensor failure or when sensor data is unreliable), rather than relying on it exclusively. This partial use maintains reliability during critical failures while minimizing the impact on normal precision control when sensors are functional.
Data Source
AI summary
The invention relates to a method for operating a brake system, in particular for motor vehicles, having an electrically controllable pressure supplying device for hydraulically actuating at least one wheel brake. The pressure supplying device includes a cylinder-piston arrangement with a hydraulic pressure chamber. The piston of the cylinder-piston arrangement being movable by an electromechanical actuator in order to generate a specificable target pressure in the hydraulic pressure chamber. An actuator torque and an actuator position of the electromechanical actuator are ascertained, and a pressure value for the pressure in the hydraulic pressure chamber is determined using the actuator toque and the actuator position taking into consideration a pressure model.