Wheel Brake Torque Limits for Regenerative Braking Control
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Solution Overview
Problem
Existing brake systems in electrified vehicles, particularly heavy-duty vehicles, face issues with brake fading due to heat buildup during prolonged braking, leading to reduced braking capability, and there is a need to improve braking action by determining optimal torque limits for various brakes to enhance electric power regeneration.
Innovation Solution
A method to determine actuator brake torque limits for each wheel based on actuator-specific torque capacity and current operational state, combined with road condition torque capability ranges estimated from lateral wheel force, friction, and vertical wheel force, ensuring the electric machine is prioritized within its limits to maximize power regeneration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brake torque limits are not determined, then actuator performance is maintained, but mechanical damage to the brake assembly occurs
Solution Approach 1:
The system performs preliminary characterization of the brake assembly to determine torque limits before normal operation. This advance preparation involves applying test torques and measuring brake disc deflection to establish safe operating parameters, preventing mechanical damage while enabling full actuator performance during subsequent operation.
Solution Approach 2:
The system continuously monitors brake disc deflection using a displacement sensor and compares it against predetermined thresholds. When the deflection exceeds the threshold, the controller reduces the actuator torque to prevent mechanical damage. This feedback loop enables dynamic torque adjustment based on real-time brake assembly conditions.
2Measurement precision
If brake torque limits are determined through traditional testing, then torque limits are established, but vehicle availability is reduced due to bench testing requirements
Solution Approach 1:
The system performs brake characterization and torque limit determination directly in the vehicle during normal operation, eliminating the need for separate bench testing facilities. The vehicle's own actuators and sensors are used to characterize the brake assembly, allowing torque limits to be established without removing the vehicle from service.
Solution Approach 2:
The system performs preliminary characterization of the brake assembly to determine torque limits before normal operation. This advance preparation involves applying test torques and measuring brake disc deflection to establish safe operating parameters, preventing mechanical damage while enabling full actuator performance during subsequent operation.
3Power
If actuator torque is increased to compensate for wear, then actuator performance is maintained, but mechanical damage to the brake assembly occurs
Solution Approach 1:
The system continuously monitors brake disc deflection using a displacement sensor and compares it against predetermined thresholds. When the deflection exceeds the threshold, the controller reduces the actuator torque to prevent mechanical damage. This feedback loop enables dynamic torque adjustment based on real-time brake assembly conditions.
Solution Approach 2:
The system dynamically adjusts actuator torque based on real-time feedback from the displacement sensor. Rather than using a fixed torque limit, the system modifies torque output according to the measured brake disc deflection, allowing optimal performance while preventing mechanical damage throughout the brake assembly lifecycle.
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 reduces the risk of overheating and ensures that brake torque is distributed optimally across actuators, enhancing electric power generation during braking and increasing the vehicle's operational distance.
Implementation Method 1
A method of determining actuator torque limits for a brake assembly is disclosed. The method includes applying a torque to a brake disc of the brake assembly, measuring a brake disc deflection with a displacement sensor
Data Source
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AI summary
The present invention relates to a method of determining actuator brake torque limits for a plurality of actuators (104), wherein each actuator (104) is operable to apply a brake torque on a wheel (102) of a vehicle (100), the method comprising determining, for each actuator (104), an actuator brake torque capability range based on an actuator specific torque capacity and a current operational state of the actuator (104); determining, for each wheel (102) of the vehicle (100), a road condition brake torque capability range based on an estimated lateral wheel force acting on the wheel (102), an estimated friction (218) between a tire surface of the wheel (102) and a road surface, and a vertical wheel force (220) acting on the wheel (102); and determining, for each actuator (104), an upper actuator brake torque limit (228) and a lower actuator brake torque limit (230) based on the actuator brake torque capability range and the road condition brake torque capability range.