EV Torque Balancing Under Battery Discharge Power Limits
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Solution Overview
Problem
Existing electric vehicle systems face challenges in managing electrical power demands to prevent exceeding the power limits of the electric energy storage device, which can affect vehicle dynamics and stability when battery output is constrained.
Innovation Solution
A method is developed to adjust the torque command of electric machines to minimize the difference in electrical power consumption between left and right machines, ensuring the total power delivery aligns with the maximum allocated discharge power, thereby limiting battery output and maintaining vehicle stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the electric energy management system limits electrical power demands on the electric energy storage device to prevent exceeding power limits, then the battery output is protected, but vehicle drivability and stability are degraded
Solution Approach 1:
The system dynamically adjusts torque commands for left and right electric machines based on real-time battery state of charge and power limits. The torque reduction value is continuously optimized to minimize power consumption difference while adapting to changing battery conditions, ensuring both battery protection and maintained drivability under varying operating conditions.
Solution Approach 2:
The system changes operational parameters by adjusting torque commands and power allocation to left and right electric machines. When battery power limits are approached, the system modifies the torque reduction value parameter to balance power consumption between machines, thereby protecting the battery while minimizing impact on vehicle performance.
2Productivity
If unequal torque commands are applied to left and right electric machines to meet power demands, then vehicle performance is optimized, but battery power limits are exceeded
Solution Approach 1:
The system implements feedback control by continuously monitoring the difference in electrical power consumption between left and right electric machines. When the state of charge falls below a threshold or power limits are approached, the system adjusts torque commands based on the calculated torque reduction value, creating a closed-loop control that ensures battery power limit compliance while maintaining vehicle performance.
Solution Approach 2:
The system applies partial torque reduction to electric machines when battery power limits are approached. Rather than completely limiting power output, the system reduces torque commands by an optimized amount that minimizes power consumption difference between machines, allowing the battery to operate within limits while still delivering acceptable vehicle performance.
3Reliability
If torque commands are reduced to stay within battery power limits, then battery output is protected, but vehicle stability is compromised
Solution Approach 1:
The system intentionally creates asymmetric torque commands for left and right electric machines when battery power limits are approached. By applying different torque reduction values to each machine based on their individual power consumption characteristics, the system protects the battery while minimizing the impact on vehicle stability through differentiated torque management.
Data Source
AI summary
Methods and systems are provided for operating an electric vehicle during conditions when output of an electric energy storage device is limited. In one example, torque commands of left and right electric machines are adjusted in equal amounts so that output of the electric energy storage device may be limited. The approach may be applied to electric machines on front and rear sides of an electric vehicle.