Electronic Parking Brake Motor Impedance Detection
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Solution Overview
Problem
Electronic parking brake systems face challenges in accurately determining motor stuck failures, as they rely on current thresholds that can lead to incorrect determinations when the stall current threshold value falls within the target current range, causing misinterpretation of normal operation versus motor stuck failures.
Innovation Solution
The system incorporates a current detector and electronic control unit that calculates the impedance of the motor using a vector sum of resistance and inductive reactance components, determining motor stuck failures based on impedance values and movement states, rather than solely relying on current thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a stall current threshold value is used to determine parking brake completion, then the determination process is simple, but motor stuck failures cannot be accurately detected when the threshold falls within the target current range
Solution Approach 1:
The patent changes the detection parameter from simple current threshold to impedance value. By calculating impedance using Z = sqrt(R² + (ωL)²) where R is resistance and L is inductance, the system can reliably distinguish motor stuck failures from normal operation regardless of current threshold settings. This parameter transformation resolves the contradiction by providing accurate detection without sacrificing operational simplicity.
2Device complexity
If current threshold alone is used for motor stuck detection, then the detection method is simple, but false determination occurs when stall current threshold falls within target current range
Solution Approach 1:
The patent introduces impedance calculation as an intermediary measurement between current detection and motor stuck determination. By measuring both resistance R and inductance L components and calculating impedance Z, the system creates a more precise indicator that mediates between the simple current measurement and the complex motor state, eliminating false determinations while maintaining reasonable system complexity.
3Reliability
If impedance calculation is used to detect motor stuck failures, then detection accuracy is improved, but system complexity increases
Solution Approach 1:
The patent replaces complex mechanical diagnostic methods with electrical impedance measurement. Instead of using mechanical sensors or complex diagnostic procedures to detect motor stuck failures, the system uses electrical measurements (resistance and inductance) to calculate impedance, providing accurate detection with relatively simple electrical circuitry and computation.
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 allows for precise and reliable detection of motor stuck failures, preventing system malfunctions and enhancing safety by accurately distinguishing between normal operation and motor stuck conditions.
Implementation Method 1
a current detector configured to detect a motor current flowing through the motor of the EPB actuator
Implementation Method 2
calculates an impedance of the motor when a motor current value detected by the current detector is higher than a preset value
Implementation Method 3
calculates an impedance of the motor using a vector sum of a resistance component and an inductive reactance component of the motor
Implementation Method 4
an EPB actuator which has a motor and provides disc brakes provided in wheels with parking brake power by rotating the motor
Data Source
AI summary
Disclosed herein are an electronic parking brake (EPB) system and a method of controlling the same. The EPB system including an EPB actuator which has a motor and provides disc brakes provided in wheels with parking brake power includes a parking switch configured to be turned on or off by a driver, a current detector configured to detect a motor current flowing through the motor of the EPB actuator, a motor driving unit configured to drive the motor of the EPB actuator, and an electronic control unit which applies a parking brake in which the motor of the EPB actuator is rotated by the motor driving unit in one direction to provide the disc brakes with the parking brake power when the parking switch is turned on, calculates an impedance of the motor when a motor current value detected by the current detector is higher than a preset value while applying the parking brake, and determines whether a motor stuck failure occurs based on the calculated impedance of the motor.