Cooperative Brake Torque Estimation for One-Pedal Deceleration
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Solution Overview
Problem
Current motor vehicle powertrain systems face challenges in efficiently managing brake torque during one-pedal driving operations, particularly when the propulsion actuator's capacity is insufficient to meet deceleration demands, leading to suboptimal vehicle control and increased system complexity.
Innovation Solution
A closed-loop feedback control system with intelligent control logic that coordinates friction brake and propulsion actuators to estimate and manage brake torque, using real-time data to calculate friction brake torque requests and optimize actuator distribution, ensuring efficient deceleration even when propulsion actuator capacity is limited.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the propulsion actuator capacity is increased to meet deceleration demands, then the braking performance is improved, but the system complexity and cost increase
Solution Approach 1:
The patent combines friction brake system and propulsion actuator braking into a unified cooperative brake system. The control module integrates torque requests from both systems and distributes them optimally, merging two separate braking mechanisms into a coordinated whole that shares the deceleration load, thereby improving overall brake torque capacity without proportionally increasing system complexity
Solution Approach 2:
The propulsion actuator serves dual functions: propulsion during acceleration and braking during deceleration. By enabling the propulsion actuator to provide braking torque in addition to the friction brake system, the system achieves multi-functionality where a single component (propulsion actuator) performs both driving and braking roles, improving brake torque capacity without adding dedicated braking components
2Productivity
If the friction brake torque is increased to compensate for insufficient propulsion actuator capacity, then the deceleration demand is met, but the wear on friction brakes increases and energy efficiency decreases
Solution Approach 1:
The control module dynamically adjusts the distribution of brake torque between friction brakes and propulsion actuator based on real-time operating conditions. During regenerative braking opportunities, the system maximizes propulsion actuator torque contribution and minimizes friction brake usage. The torque distribution is continuously optimized to meet deceleration demands while preserving energy efficiency and reducing friction brake wear
Solution Approach 2:
The system changes the operational parameters of the propulsion actuator by adjusting torque requests within its capacity limits. The control module calculates optimal torque distribution parameters that maximize the use of propulsion actuator braking (which is energy-efficient through regenerative braking) while minimizing friction brake application, thereby maintaining deceleration capability while improving energy efficiency
3Speed
If the brake torque distribution is optimized in real-time, then the response time is improved, but the computational complexity increases
Solution Approach 1:
The control module implements a feedback mechanism that continuously monitors the actual brake torque contribution from both friction brakes and propulsion actuator. Based on this feedback and the driver's torque request, the system dynamically adjusts the torque distribution in real-time. This closed-loop control ensures rapid response to changing deceleration demands while using measured actual performance to guide control decisions
Solution Approach 2:
The control module performs preliminary calculations of optimal torque distribution based on the driver's torque request and current system state before actuation. By pre-calculating the optimal torque split between friction brakes and propulsion actuator based on available capacity and current operating conditions, the system prepares the brake torque distribution in advance, enabling rapid response when deceleration is commanded without excessive computational complexity during real-time execution
Data Source
AI summary
A method of operating a vehicle includes a vehicle controller receiving an operator-input vehicle control command with an associated torque request, and identifying any propulsion actuator constraints that limit a brake torque capacity available from the vehicle powertrain. Using the propulsion actuator constraint(s) and torque request, the controller determines a propulsion brake torque distribution for the vehicle's road wheels and a maximum brake torque capacity for the powertrain actuator(s). A first brake torque request is determined using the propulsion brake torque distribution and a vehicle control mode of the powertrain system, and a second brake torque request is determined using the maximum brake torque capacity and the vehicle control mode. A friction brake torque command is determined by arbitrating between the first and second brake torque requests. The vehicle controller transmits the friction brake torque command to the friction brake system and a powertrain brake command to the powertrain actuator(s).