Electro-Mechanical Brake Force Estimation Using Current and Piston Position
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Solution Overview
Problem
Existing electro-mechanical brakes (EMBs) face challenges in accurately estimating braking force during traveling without additional calibration due to changes in brake pad wear and stiffness, which can lead to braking heterogeneity and potential accidents.
Innovation Solution
An electro-mechanical brake system that includes a current detection unit, position detection unit, and actual braking force value detection unit, utilizing first and second maps to correlate motor current, piston position, and braking force, enabling accurate braking force estimation without additional calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration is performed during traveling to update braking force data, then measurement precision of braking force is improved, but safety is worsened due to potential braking heterogeneity and traffic accidents
Solution Approach 1:
The system performs calibration and updates the force map during periods when the vehicle is not traveling (e.g., when the driver opens the door or starts up the vehicle). This preliminary action ensures that the braking force data is updated before traveling begins, avoiding the need to perform calibration during traveling and thus preventing braking heterogeneity and potential accidents while maintaining measurement precision.
2Reliability
If calibration is performed only when the driver opens the door or starts up the vehicle, then safety is improved by avoiding calibration during traveling, but measurement precision deteriorates because the force map cannot reflect real-time changes in brake pad wear and stiffness
Solution Approach 1:
The system uses feedback from multiple sensors (motor current sensor, piston position sensor, wheel speed sensor) to continuously monitor the actual braking force during traveling. The estimated braking force is compared with the actual braking force, and the difference is used to update the force map in real-time without requiring calibration during traveling. This feedback mechanism maintains measurement precision while ensuring safety by avoiding calibration during active driving.
Solution Approach 2:
The system performs self-updating of the force map by using its own operational data (motor current, piston position, wheel speed) to estimate and refine braking force characteristics. This self-service capability allows the system to adapt to changes in brake pad wear and stiffness without external calibration interventions during traveling, maintaining both safety and measurement precision.
3Measurement precision
If a force sensor is mounted on the electro-mechanical brake to measure braking force, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system uses existing components (motor, piston, sensors already present in the electro-mechanical brake system) as intermediaries to estimate braking force. Instead of directly measuring braking force with a dedicated force sensor, the system uses motor current and piston position data as intermediary parameters to calculate the braking force, thereby avoiding the need for additional expensive force sensors while maintaining measurement precision.
Solution Approach 2:
The system replaces the mechanical force sensor measurement approach with an estimation approach based on electrical and positional parameters. By substituting the direct mechanical measurement (force sensor) with an estimation method using motor current and piston position data, the system reduces device complexity and cost while maintaining the ability to accurately determine braking force.
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
The system accurately detects braking force changes during traveling, ensuring stable vehicle performance and reducing braking heterogeneity by using current and piston position data to adjust braking force effectively.
Implementation Method 1
an actuator that is driven by a motor is mounted on a brake caliper. The electro-mechanical brake presses a wheel disk using a motor
Implementation Method 2
The brake pad presses the wheel disk to generate the braking force
Data Source
AI summary
An electro-mechanical brake including a piston configured to push a brake pad toward a wheel disk through driving of a motor, the electro-mechanical brake including: a current detection unit configured to detect an actual current value flowing through the motor; a position detection unit configured to detect an actual piston position of the piston; an effective value extraction unit configured to filter the actual current value and extract an effective value from the actual current value; and an actual braking force value detection unit configured to detect an actual braking force value based on a first map, a second map, the actual piston position, and the effective value, wherein the first map is a map in which a correlation relationship between a current flowing through the motor, a position of the piston, and a braking force in a first state is converted into data, the second map is a map in which the current flowing through the motor and a factor in the first state are converted into data, and the factor is a ratio of the braking force to the current flowing through the motor.