Electro-mechanical Brake Clamping Force Estimation
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Solution Overview
Problem
The existing 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 do not consider the hysteresis characteristics of the piston's moving path, which affects braking force estimation.
Innovation Solution
An electro-mechanical brake system that includes a position detection unit, a current detection unit, and a motor controller to calculate the contact point and braking force by considering the hysteresis characteristics of the piston's position, using a current sensor and a position sensor to estimate the clamping force without 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 approach. Instead of directly measuring clamping force with a load sensor, the system measures the current consumed by the motor during brake pad actuation. The motor controller calculates clamping force based on the relationship between motor current and piston displacement, substituting a complex mechanical sensing system with a simpler electrical measurement system that uses existing motor control infrastructure.
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 approach. Instead of directly measuring clamping force with a load sensor, the system measures the current consumed by the motor during brake pad actuation. The motor controller calculates clamping force based on the relationship between motor current and piston displacement, substituting a complex mechanical sensing system with a simpler electrical measurement system that uses existing motor control infrastructure.
Solution Approach 2:
The patent makes the motor serve dual functions: it not only actuates the brake pads but also provides the measurement signal through its current consumption. The motor controller utilizes the electrical characteristics of the motor itself to infer clamping force, eliminating the need for separate sensing components. This self-service approach reduces manufacturing cost by repurposing existing system components.
3Ease of manufacture
If current sensor is used to estimate clamping force, then manufacturing cost is reduced, but measurement accuracy deteriorates due to noise
Solution Approach 1:
The patent introduces piston position as an intermediary variable to bridge the relationship between motor current and clamping force. Instead of directly using noisy current measurements, the system first determines piston position based on motor current and control signals, then calculates clamping force by combining position information with current data. This intermediary approach filters out measurement noise and improves estimation accuracy.
Solution Approach 2:
The patent implements a feedback mechanism where the motor controller continuously monitors motor current and adjusts the actuation signal based on the relationship between current, piston position, and desired clamping force. The system uses feedback from position detection (through motor control) to refine the clamping force estimation, compensating for noise in the current measurements and improving overall measurement accuracy.
4Device complexity
If piston moving path is not considered, then calculation complexity is reduced, but braking force estimation accuracy deteriorates due to hysteresis
Solution Approach 1:
The patent applies preliminary action by pre-establishing the relationship between piston position, moving direction, and braking force characteristics. The motor controller stores or pre-calculates the hysteresis curves that represent different moving paths (extending vs. retracting). When estimating braking force, the system retrieves the appropriate curve based on the current moving direction, avoiding complex real-time calculations while maintaining high accuracy.
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 accurate estimation of clamping force and braking force, improving the precision of braking control by accounting for the piston's position and hysteresis characteristics, thereby enhancing braking stability and reducing manufacturing costs and size.
Implementation Method 1
a piston configured to push a brake pad towards a wheel disc by driving a motor
Implementation Method 2
a brake pad disposed on one side of the wheel disc, the brake pad to contact the wheel disc
Data Source
AI summary
The present disclosure in some embodiments provides an electro-mechanical brake comprising a piston configured to push a brake pad towards a wheel disc by driving a motor, the electro-mechanical brake comprising: a position detection unit detecting a position of the piston; a current detection unit detecting a value of current flowing through the motor; a motor controller controlling a motor to move the piston toward the wheel disc for a preset time when a vehicle is stopped; and a contact point calculation unit calculating a contact point that is a position of the piston when the brake pad starts to contact with the wheel disc, based on a first position that is a position of the piston when a first current value is detected, using the current detection unit.