Electric Machine Torque Control via Coil Temperature Estimation
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Solution Overview
Problem
Inaccurate oil temperature readings in electric machines can lead to incorrect torque adjustments, limiting the performance of vehicles powered by electric machines.
Innovation Solution
A system that includes a traction motor, a generator, and an oil circulation path with sensors, where a controller alters the current provided to the motor and generator based on the temperature of their windings to maintain a requested torque output, even in the event of a fault in the oil temperature sensor, using an estimation method that calculates the oil temperature from the coil temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oil temperature sensor is used to monitor temperature, then temperature monitoring is achieved, but measurement accuracy deteriorates when sensor fault occurs
Solution Approach 1:
The patent uses coil temperature as an intermediary parameter to estimate oil temperature when the oil temperature sensor fails. Instead of directly measuring oil temperature with a faulty sensor, the system measures coil temperature (which remains reliable) and uses it as a proxy to infer oil temperature, thereby maintaining measurement accuracy through an alternative measurement path.
Solution Approach 2:
The system performs preliminary detection of sensor faults and switches to an alternative measurement strategy before complete failure occurs. By continuously monitoring the relationship between coil temperature and oil temperature, the system can detect when the oil temperature sensor becomes unreliable and proactively switch to using coil temperature for torque adjustments, preventing performance degradation.
2Productivity
If torque adjustments are made based on temperature readings, then performance is optimized, but incorrect torque adjustments occur when temperature readings are inaccurate
Solution Approach 1:
The system implements feedback control by continuously monitoring both coil temperature and oil temperature (when available) and using this information to adjust torque in real-time. When the oil temperature sensor fails, the feedback mechanism switches to using only coil temperature data, allowing the system to maintain optimal torque adjustments based on the most reliable temperature information available, thus preserving productivity while ensuring reliability.
3Measurement precision
If oil temperature is monitored directly, then accurate oil temperature measurement is achieved, but system complexity increases with additional sensors
Solution Approach 1:
The patent makes the coil temperature sensor multi-functional by using it for both its primary purpose (monitoring coil temperature for insulation protection) and as a substitute for oil temperature measurement when the dedicated oil temperature sensor fails. This universal approach allows the system to maintain oil temperature monitoring capability without requiring additional sensors, thereby reducing device complexity while preserving measurement precision.
Data Source
AI summary
A vehicle having at least two electric machines includes an oil circulation path that circulates oil through the electric machines. A controller commands the electric machines to fulfill torque demands. The controller utilizes the oil temperature in the oil circulation path to control the commanded torque output by the electric machines. In the event of a failure or fault in an oil temperature sensor, the controller estimates the oil temperature from the temperature of coils within at least one of the electric machines. The estimated oil temperature is utilized instead of the sensed oil temperature to control the torque outputs to satisfy torque demands.