Electric Brake Clamping Force Determination via Motor Current
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Solution Overview
Problem
Current methods for determining the application force of electric brakes using DC motors in vehicles rely on dedicated sensors, which are costly and not cost-effective, especially for secondary functions like electric parking brakes.
Innovation Solution
A method that measures the current strength signal from the DC motor using high-frequency sampling and filtering to derive the application force without the need for force sensors, by generating trigger signals based on threshold crossings and incrementing/decrementing a rotation signal to calculate the number of revolutions, allowing for the determination of clamping force or surface pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dedicated force sensors or angle sensors are used to determine application force, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The DC motor serves itself by using its own current signal for force determination. The evaluation unit processes the motor's current signal to extract application force information, eliminating the need for external force sensors. The motor's operational parameters are reused for dual purposes: driving the brake and measuring the applied force.
Solution Approach 2:
The patent replaces mechanical force sensors with an electrical signal processing system. Instead of using physical sensors to detect force, the system uses electrical current signal analysis through high-pass filtering and trigger signal generation to determine application force, substituting a mechanical measurement system with an electrical one.
2Measurement precision
If dedicated force sensors are used, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The current signal from the DC motor is used for multiple purposes: controlling the motor operation and determining the application force. This multi-functional use of the existing current signal eliminates the need for separate sensing components, reducing manufacturing costs while maintaining measurement capability.
Solution Approach 2:
The system uses the motor's own operational current signal to determine force, making the system self-sufficient and eliminating the need for additional expensive sensing components that would increase manufacturing costs.
3Measurement precision
If high-frequency sampling is used to measure current signal, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The system applies high-frequency sampling only when necessary for accurate force determination, rather than continuously at maximum frequency. The evaluation unit processes current signals with sufficient frequency to capture the relevant mechanical motion information, avoiding excessive energy consumption while maintaining adequate measurement precision.
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
Enables cost-effective determination of application force without additional sensors, utilizing existing current signals for electric brake operation, thereby reducing costs in DC motors across various vehicle applications.
Implementation Method 1
The electric brake includes in particular the DC motor (20). The DC motor is designed for use in a motor vehicle (10).
Implementation Method 2
A first useful signal (41) is generated by filtering the measured current intensity signal using a high-pass filter (53).
Implementation Method 3
A large number of trigger signals (48) are generated when the first useful signal (41) rises above a first threshold value (SW1) and/or the first useful signal (41) falls below a second threshold value (SW2).
Data Source
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AI summary
The invention relates to a method for determining the clamping force (64) of an electric brake (12). The electric brake (12) includes a DC motor (20) and is used in a motor vehicle (10). First, a current signal (40) of the DC motor (20) is measured at a sampling frequency of at least 2 kilohertz. A first useful signal (41) is generated by high-pass filters (53) of the measured current signal (40). At least one trigger signal (48) is generated when the magnitude of the first useful signal (41) exceeds a first threshold value (SW1) in an increasing manner. A revolution signal (45) is incremented or decremented depending on the polarity (51) of a voltage (50) applied to the DC motor (20). This allows the number of revolutions (N) of a braking component of the electric brake (12) to be obtained. The clamping force (64) is determined as a function of the number of revolutions (N).