Closed-Loop EV Power Limiting for Battery-Safe Torque Control
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Solution Overview
Problem
Conventional battery management systems face challenges in accurately estimating battery power limits, leading to underutilization of available resources and safety concerns due to conservative efficiency factor assumptions and complex, memory-intensive offline efficiency maps.
Innovation Solution
A method involving closed-loop control using a battery power limit as a setpoint and actual battery power as feedback to calculate an electric power reference, determining torques for electric motors to operate within safe power limits while maximizing battery usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant efficiency factor is used to ensure battery safety, then reliability is improved, but productivity deteriorates due to underestimation of available battery power
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant efficiency factor to a dynamic efficiency map that adapts to varying operating conditions. The efficiency map is updated in real-time based on measured actual efficiency values during vehicle operation, allowing the system to optimize battery power utilization while maintaining safety across different driving scenarios.
Solution Approach 2:
The patent implements parameter changes by modifying the efficiency factor from a fixed constant to a variable parameter that changes based on operating conditions. The system measures actual efficiency under different conditions (load, temperature, state of charge) and uses these measurements to update the efficiency map, thereby optimizing the balance between safety and power utilization.
2Productivity
If a predetermined offline efficiency map is used to maximize battery power utilization, then productivity is improved, but device complexity increases due to memory and computational requirements
Solution Approach 1:
The patent applies partial action by implementing a simplified efficiency map that captures the most critical operating conditions rather than attempting to model all possible scenarios. The system focuses on measuring and storing efficiency data for key operating points, reducing memory requirements while maintaining sufficient accuracy for safe and efficient battery management.
Solution Approach 2:
The system performs self-service by automatically measuring actual efficiency during normal vehicle operation and using these measurements to update the efficiency map without requiring external calibration or complex offline simulations. The battery management system learns and adapts to its own operating characteristics over time.
3Productivity
If a predetermined offline efficiency map is used to estimate electrical power, then productivity is improved, but measurement precision deteriorates due to artifacts and overshooting near power limits
Solution Approach 1:
The patent implements feedback by continuously measuring actual battery power and efficiency during operation, then using these measurements to correct and update the efficiency map. The system compares estimated power (based on the efficiency map) with actual measured power, and uses the difference to refine the efficiency values, thereby eliminating artifacts and overshooting near power limits.
Data Source
AI summary
A method for determining one or more torques to be applied by one or more electric motors of a vehicle is provided. The method comprising: obtaining a power request for the one or more electric motors; performing a closed loop control using a discharge battery power limit as a setpoint and an actual battery power as a feedback to obtain a control action; calculating an electric power reference using the power request and the control action; and determining the one or more torques to be applied by the one or more electric motors using the electric power reference.