Electro-Mechanical Brake Clamping Force Estimation via Piston Hysteresis
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Solution Overview
Problem
Electro-mechanical brakes face challenges in accurately estimating clamping force due to measurement noise from current sensors, leading to reduced estimation accuracy compared to load sensors, and the need for higher braking response and durability, which complicates design and increases manufacturing costs.
Innovation Solution
An electro-mechanical brake system that includes a position detection unit, a calculation unit, and a braking force calculation unit to estimate clamping force based on the position of the piston, considering hysteresis characteristics, using a current sensor instead of a load sensor, and employing a low pass filter to reduce noise in current measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a load sensor is used to measure clamping force, then measurement accuracy is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent replaces the mechanical load sensor with an electrical measurement system. Instead of directly measuring clamping force with a mechanical sensor, the system measures the current consumed by the motor during brake pad actuation. The control unit calculates clamping force based on the relationship between motor current and piston displacement, thereby substituting a complex mechanical sensing system with a simpler electrical measurement approach that uses existing motor control infrastructure.
Solution Approach 2:
The patent introduces current as an intermediary parameter to indirectly measure clamping force. Rather than directly sensing the mechanical force, the system measures the electrical current drawn by the motor, which serves as a proxy indicator. The control unit then correlates this current measurement with piston position data to estimate the actual clamping force applied to the brake pads, using the current as a mediating variable in the measurement process.
2Measurement precision
If a load sensor is used to measure clamping force, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
The patent replaces the mechanical load sensor with an electrical measurement system. Instead of directly measuring clamping force with a mechanical sensor, the system measures the current consumed by the motor during brake pad actuation. The control unit calculates clamping force based on the relationship between motor current and piston displacement, thereby substituting a complex mechanical sensing system with a simpler electrical measurement approach that uses existing motor control infrastructure.
Solution Approach 2:
The patent employs inexpensive current sensing capabilities that are already integrated into standard motor control systems rather than expensive dedicated load sensors. By utilizing the existing current measurement infrastructure of the motor driver, the system achieves clamping force estimation without requiring additional costly sensing components, thereby reducing overall manufacturing cost while maintaining functional accuracy.
3Device complexity
If current sensor is used to estimate clamping force, then device complexity and manufacturing cost are reduced, but measurement accuracy deteriorates due to measurement noise
Solution Approach 1:
The patent implements a feedback mechanism where the control unit continuously monitors both the current consumed by the motor and the position of the piston. By comparing the measured current with the expected current-piston position relationship, the system can detect and compensate for measurement deviations. The control unit uses this feedback information to refine the clamping force estimation, thereby improving accuracy despite the inherent noise in current measurements.
Solution Approach 2:
The patent makes the current measurement serve multiple functions: it not only provides information for clamping force estimation but also enables monitoring of motor operating conditions, detection of abnormal states, and verification of piston movement. This multi-functional use of the current sensor data allows the system to compensate for measurement noise by cross-validating readings against expected operational patterns, thereby improving overall measurement reliability without adding dedicated noise-filtering hardware.
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 accurate estimation and calculation of braking force, improving control precision and reducing manufacturing costs by eliminating the need for load sensors while maintaining high braking performance.
Implementation Method 1
a piston configured to press the brake pads toward the wheel disc by driving a motor
Implementation Method 2
a wheel disc, a pair of brake pads disposed on both sides of the wheel disc, and a piston configured to press the brake pads toward the wheel disc
Data Source
AI summary
An electro-mechanical brake configured such that a piston pulls a brake pad toward a wheel disc by driving a motor is disclosed. The electro-mechanical brake comprising: a hysteresis data storage unit storing rising-section function data on a rising section in which braking force increases as the piston moves toward the wheel disc, and falling-section function data on a falling section in which the braking force decreases as the piston moves away from the wheel disc; a position detection unit detecting a position of the piston; a calculation unit calculating a differential value of the position of the piston with respect to time; a past state data storage unit storing data on a preceding section corresponding to a preceding piston position; and a braking force calculation unit calculating the braking force based on the differential value of the piston position and the data on the preceding section.