Rotor Temperature Estimation for Electric Vehicles
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Solution Overview
Problem
Existing rotor temperature estimation methods in electric vehicles are inadequate during 'hot starts,' leading to potential overheating due to slow response rates and inaccurate initial temperature estimates, which can result in reduced motor performance and lifespan.
Innovation Solution
Implementing a fast-mode rotor temperature estimator with a temporarily increased limit value for rapid temperature estimation during high torque conditions, followed by a normal-mode estimator for sustained operation, utilizing both thermal and resistance models to accurately track rotor temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a normal-mode rotor temperature estimator is used, then the temperature estimation is stable and accurate under normal conditions, but the response rate is slow during hot starts causing potential overheating
Solution Approach 1:
The patent applies dynamics by making the estimator mode changeable based on operating conditions. The system dynamically switches between normal-mode and fast-mode estimators using a mode selection mechanism that monitors parameters like motor current and temperature differential. This allows the system to adapt its response characteristics to match the actual thermal state of the motor, resolving the contradiction between stability and rapid response.
Solution Approach 2:
The patent changes the estimation parameters by using different limit values for temperature estimation in different modes. In fast-mode, a higher limit value is used to allow faster temperature estimation during hot starts, while in normal-mode, a lower limit value maintains accuracy. This parameter change enables the system to overcome the slow response issue without sacrificing overall estimation reliability.
2Power
If full torque is applied during hot start with inaccurate temperature estimation, then motor performance is maximized, but overheating risk increases due to slow temperature tracking
Solution Approach 1:
The patent applies preliminary action by implementing a fast-mode estimator that proactively estimates rotor temperature more quickly during hot starts before the normal-mode estimator would take effect. This preliminary fast estimation allows the control system to make informed torque decisions earlier, preventing overheating while maintaining performance. The mode selection mechanism triggers this preliminary action based on detected hot start conditions.
Solution Approach 2:
The patent uses feedback by continuously monitoring temperature estimates and comparing them against limit values to determine when to switch between modes. The system feedback loop detects when the motor is in a hot start state and activates the appropriate estimation mode, ensuring that torque application is always based on the most accurate available temperature information, thereby preventing overheating while maximizing performance.
3Speed
If a fast-mode rotor temperature estimator with increased limit value is used during hot starts, then temperature estimation response rate increases, but system complexity increases due to mode switching mechanism
Solution Approach 1:
The patent applies segmentation by dividing the temperature estimation system into distinct modes (fast-mode and normal-mode) with different characteristics. Each mode is handled by separate estimation logic with appropriate limit values, and a mode selection mechanism determines which segment is active. This segmentation allows the system to achieve fast response when needed while keeping the overall architecture manageable through clear separation of concerns.
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 effectively mitigates overheating risks by rapidly estimating rotor temperature during 'hot starts' and maintaining accurate tracking, thereby protecting the electric motor from damage and ensuring reliable performance.
Implementation Method 1
a resistance rotor temperature estimator providing a second temperature estimate for the rotor of the electric motor
Data Source
AI summary
In accordance with exemplary embodiments, rotor temperature estimation is provided for estimating rotor temperatures of an electric motor in an electric vehicle. A method comprises estimating a rotor temperature in a controller for an electric motor of a vehicle using a fast-mode rotor temperature estimator for a time interval, and then deactivating the fast-mode rotor temperate estimator after the time interval and activating a normal-mode rotor temperature estimator in the controller for the electric motor of the vehicle. A system comprises an electric motor, a resistance rotor temperature estimator including a limit value limiting a temperature estimate increase for temperature estimates, and a controller for the electric motor, which uses the temperature estimate and is configured to temporarily increase the limit value of the resistance rotor temperature estimator providing a fast-mode rotor temperature estimate.