Electro-Mechanical Brake Home Position Sensing Without Load Sensors
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Solution Overview
Problem
Existing electro-mechanical brakes (EMBs) face challenges in accurately calculating the home position due to errors in estimating clamping force using current sensors, leading to unstable braking performance.
Innovation Solution
The electro-mechanical brake system incorporates a current sensor to measure motor current and a position sensor to track the pressing unit's position, utilizing two check points (C1 and C2) to calculate the home position or contact point with higher accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a load sensor is used to measure clamping force, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces the mechanical load sensor with an electrical measurement approach. Instead of directly measuring clamping force with a load sensor, the system measures the current consumed by the motor during brake operation. Since the motor current is directly related to the torque and thus the clamping force, this electrical measurement method achieves the same measurement objective without requiring additional mechanical sensors, thereby reducing device complexity while maintaining measurement capability.
2Measurement precision
If a load sensor is mounted in the EMB, then clamping force measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent utilizes the existing motor's current sensor (which is already present for motor control) to infer clamping force, rather than installing an additional expensive load sensor. The current sensor is a standard component in the motor control system, and by cleverly using its data for dual purposes (motor control and force measurement), the system avoids the need for expensive additional sensors, thereby reducing manufacturing cost while maintaining measurement accuracy.
3Device complexity
If clamping force is estimated by measuring motor current, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent employs a feedback mechanism where the measured motor current is continuously monitored and used to calculate the clamping force. The system establishes a relationship between motor current and clamping force through calibration or theoretical modeling, then uses this relationship in real-time to determine the actual clamping force applied. This feedback approach allows the system to compensate for variations in motor characteristics and operating conditions, thereby improving measurement precision without adding complex hardware.
4Device complexity
If clamping force is estimated by measuring motor current, then device complexity is reduced, but home position calculation accuracy deteriorates
Solution Approach 1:
The patent performs preliminary calibration or characterization of the motor-current to clamping-force relationship before actual braking operation. During this preliminary phase, the system establishes the specific relationship between motor current and clamping force for that particular brake assembly, taking into account factors like friction pad characteristics and motor efficiency. This preliminary action creates a customized calibration curve or lookup table that is then used during normal operation to accurately determine home position and clamping force, thereby compensating for the lack of direct load sensing.
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 more precise calculation of the home position, thereby enhancing the stability and reliability of the braking performance in EMBs.
Implementation Method 1
a current sensor configured to measure an intensity (i) of current flowing through the motor
Implementation Method 2
a position sensor configured to measure a position (d) of the pressing unit
Implementation Method 3
a motor configured to supply power to the pressing unit so that the pressing unit presses the friction pad
Implementation Method 4
a friction pad configured to face the brake disc and press the brake disc
Data Source
AI summary
An electro-mechanical brake includes: a brake disc; a friction pad; a pressing unit configured to press the friction pad toward the brake disc; a motor supplying power to the pressing unit; a current sensor; a position sensor configured to measure a position of the pressing unit; and an initial position calculating unit calculating at least one of a home position or a contact point of the pressing unit, wherein the pressing unit is configured to pass through a first check point at which a first current is measured, and a second check point at which a second current greater than the first current is measured, and wherein the initial position calculating unit calculates at least one of the home position or the contact point based on the first current, the first check point, the second current, and the second check point.