Vehicle Brake Torque Control for Load-Dependent Energy Capture
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Solution Overview
Problem
Existing brake systems in vehicles with electric drive motors face challenges in optimizing regenerative braking energy capture across varying load conditions, leading to either over-braking or underutilization of energy due to insensitive pedal feedback, particularly in commercial vehicles with significant weight differences between loaded and unloaded states.
Innovation Solution
A method and control system that adjust non-friction braking torques based on vehicle load, providing different non-friction braking limits for each load condition to optimize energy capture while maintaining vehicle handling, by using a controller to manage regenerative and friction braking systems dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the brake system is configured to maximize non-friction braking at the rear axle for the fully loaded vehicle, then energy capture is maximized, but the brake system may over brake at the rear axle when the vehicle is unloaded
Solution Approach 1:
The brake control system dynamically adjusts the distribution of braking torque between friction and non-friction brakes based on real-time vehicle load conditions. The controller receives load information and continuously modifies the braking torque allocation to optimize energy capture while preventing over-braking, ensuring reliable vehicle handling across varying load states.
Solution Approach 2:
The system changes the braking torque parameters based on vehicle load conditions. When the vehicle transitions from loaded to unloaded state, the controller adjusts the non-friction braking torque limit to prevent excessive braking force that would compromise vehicle handling, while still maintaining effective energy capture during braking events.
2Ease of operation
If the brake pedal travel is mapped the same for the loaded and unloaded conditions, then the brake system is simple to control, but the brake pedal may be too sensitive when the vehicle is in the unloaded condition
Solution Approach 1:
The brake pedal sensitivity is dynamically adjusted based on vehicle load detection. When the vehicle is unloaded, the system modifies the relationship between brake pedal travel and braking torque application to reduce sensitivity, preventing overly aggressive braking responses while maintaining straightforward pedal operation for the driver.
3Reliability
If the brake system is configured to maximize non-friction braking at the rear axle for the unloaded vehicle, then sensitivity is improved, but the brake system may not utilize all of the available non-friction braking when the vehicle is loaded
Solution Approach 1:
The controller adjusts the non-friction braking torque parameters based on detected vehicle load conditions. When the vehicle is loaded, the system increases the available non-friction braking torque capacity to fully utilize regenerative braking potential, while when unloaded, it maintains appropriate sensitivity by limiting torque to match the lower vehicle mass and braking requirements.
Data Source
AI summary
A method for controlling a brake system in a vehicle includes providing a first non-friction braking torque for an axle of the vehicle when the vehicle has a first load. A second non-friction braking torque lower than the first non-friction braking torque is provided for the axle when the vehicle has a second load lower than the first load. Non-friction braking at the axle is limited by the first and second non-friction braking torques when the vehicle has the first and second loads, respectively.