Brake Factor Offset Correction for Electric Vehicle Braking Linearity
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Solution Overview
Problem
The friction coefficient of brake pads in electric vehicle brake systems varies with temperature, leading to uneven braking linearity and a heterogeneous braking experience due to changes in the brake factor, which is calculated using a constant value including the friction coefficient, piston area, and effective radius.
Innovation Solution
A system and method that estimates the brake factor by determining activation conditions based on deceleration, wheel speed, and pressure signals, calculates a brake factor offset by comparing estimated and previous factors, and updates this offset to correct the friction coefficient, thereby maintaining consistent braking linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a constant brake factor is used for calculating target braking hydraulic pressure, then the control system is simple, but the braking linearity becomes uneven due to friction coefficient changes with temperature
Solution Approach 1:
The brake factor is transformed from a static constant value to a dynamic value that changes based on brake temperature. The controller estimates the brake factor by multiplying a reference brake factor by a temperature coefficient determined from the brake temperature, allowing the system to adapt to temperature variations and maintain consistent braking linearity throughout the braking process.
Solution Approach 2:
The invention changes the parameter of the brake factor from a fixed constant to a temperature-dependent variable. By introducing a temperature coefficient that varies with brake temperature, the system dynamically adjusts the brake factor to compensate for friction coefficient changes, thereby maintaining reliable braking linearity without excessive system complexity.
2Reliability
If the brake factor is adjusted to compensate for friction coefficient changes, then the braking linearity is improved, but the control system complexity increases
Solution Approach 1:
The system uses brake temperature as feedback to dynamically adjust the brake factor. The controller continuously monitors brake temperature and uses this information to determine the appropriate temperature coefficient, which then modifies the brake factor for target braking hydraulic pressure calculation. This feedback mechanism improves braking linearity while keeping the control logic relatively simple.
Solution Approach 2:
The system uses readily available sensor data (brake temperature from the existing sensor network) to automatically adjust the brake factor without requiring additional complex hardware or manual intervention. The controller self-regulates the braking pressure calculation based on the temperature conditions, maintaining braking linearity through self-service adjustment.
3Ease of operation
If a fixed brake factor is used, then the control calculation is simple, but the braking feeling becomes heterogeneous due to temperature variations
Solution Approach 1:
The brake factor transitions from a static fixed value to a dynamic value that adapts to brake temperature conditions. The controller calculates the target braking hydraulic pressure using the temperature-adjusted brake factor, which maintains consistent braking feeling across different temperature conditions while keeping the calculation method straightforward and integrated into the existing control flow.
Data Source
AI summary
The present disclosure provides a system and a method for correcting a friction coefficient of a brake pad for a vehicle, which can estimate a brake factor including a friction coefficient of a brake pad, and ultimately correct the brake factor through the calculation and the update of a brake factor offset based on the estimated brake factor, thereby enhancing the braking linearity of an electric brake system.