Electro-Mechanical Brake Force Estimation Without In-Drive Calibration
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Solution Overview
Problem
Existing electro-mechanical brakes (EMBs) face challenges in accurately estimating braking force during traveling without performing additional calibration, as the state of the brake pad changes due to wear and stiffness variations.
Innovation Solution
The EMB employs a control method that generates and utilizes two maps: a first map correlating current, piston position, and braking force, and a second map representing the ratio of braking force to current. These maps allow the EMB to accurately detect the actual braking force value even when the brake pad state changes during traveling.
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 driver discomfort and traffic accidents
Solution Approach 1:
The system performs calibration during stationary periods (vehicle startup, door opening, or when vehicle speed is below threshold) before actual driving begins. This preliminary calibration updates the force map and stiffness values without interfering with driving operations, ensuring accurate braking force estimation is ready before traveling while maintaining safety during actual driving
2Reliability
If calibration is performed only when driver opens door or starts up vehicle, then safety is maintained, but measurement precision deteriorates as brake pad wear and stiffness changes are not reflected in real-time
Solution Approach 1:
The system continuously monitors vehicle speed and automatically triggers calibration when the vehicle is stationary or moving below a threshold speed. This feedback mechanism ensures that calibration is performed at appropriate moments to update braking force data without compromising safety, while still capturing real-time changes in brake pad wear and stiffness
Solution Approach 2:
The calibration timing is made dynamic rather than static - instead of fixed calibration only at startup, the system adapts calibration timing based on real-time vehicle operating conditions (speed thresholds). This allows the system to perform calibration when safe to do so while maintaining up-to-date braking force estimation throughout the vehicle's operation
3Measurement precision
If force sensor is mounted on electro-mechanical brake to measure braking force, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The electro-mechanical brake system performs self-calibration by utilizing its own operational data (motor current, piston position, vehicle speed) and environmental feedback to update its braking force characteristics. The system serves its own measurement needs through automatic calibration routines that establish the relationship between actuator input and braking output without requiring external force sensors
Solution Approach 2:
The system replaces direct mechanical force measurement (using force sensors) with an indirect measurement approach based on electrical and positional parameters. By measuring motor current, voltage, and piston position - which are easier to measure electrically and mechanically - and using calibration-derived relationships, the system substitutes complex force sensing with simpler electrical measurements combined with computational modeling
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 the EMB to accurately detect and adjust braking force without additional calibration, ensuring stable vehicle behavior and reducing uncomfortable braking, even when the brake pad state changes due to wear or stiffness variations during traveling.
Implementation Method 1
an actuator driven by a motor is mounted on a brake caliper... a motor starts to rotate to move a piston forward
Implementation Method 2
The electro-mechanical brake generates friction braking force... The brake pad presses the wheel disc so that the braking force is generated
Data Source
AI summary
An electro-mechanical brake includes a piston driven by a motor to push a brake pad toward a wheel disc. The brake also includes: a current detection unit for current flowing through the motor; a piston position detection unit; a map generating unit and a braking force value detection unit. When power is applied to the vehicle at start-up, the first map comprises data correlating current flowing through the motor, position of the piston, and braking force, the second map comprises data of is a map of the current flowing through the motor and a factor are converted into data with reference to the first state, and the factor is a ratio of the braking force to the current flowing through the motor. A braking force value detection detects braking force based on piston position, a current value in the motor, the first map, and the second map.