Vehicle Driveline Shift Control for Electrical Machine Thermal Balancing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The differential thermal stress caused by non-symmetrical operation of electrical machines in a vehicle powertrain leads to uneven aging of the machines and their associated power electronics, reducing the overall service life of the powertrain.
Innovation Solution
A method is introduced where, upon detecting a shift to non-symmetrical operation, the powertrain transitions into a preconditioning mode before the shift, where the electrical machine with higher torque or torque gradient is operated with a limited torque or torque gradient to reduce its temperature and that of its power electronics, while the other machine compensates to maintain performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-symmetrical operation is used during shift execution, then shift performance is improved, but thermal load and aging of one electrical machine increases
Solution Approach 1:
The control device performs preliminary cooling action by reducing the torque of the first electrical machine before the shift operation begins. This preemptive measure lowers the temperature of the electrical machine and its power electronics before they are subjected to high thermal stress during non-symmetrical shift execution, thereby extending their service life while maintaining shift performance
2Ease of operation
If one electrical machine is loaded with higher torque during shift, then shift control is improved, but differential thermal stress between machines increases
Solution Approach 1:
The control device applies preliminary anti-action by reducing the torque of the first electrical machine before differential thermal stress can develop. This countermeasure offsets the potential harmful thermal effects that would otherwise occur during non-symmetrical operation, allowing shift control to proceed without excessive thermal stress accumulation
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 reduces thermal stress and matches the thermal loads of both electrical machines and their power electronics, thereby extending the service life of the powertrain by ensuring more even aging and performance.
Implementation Method 1
the first electrical machine and the second electrical machine are each loaded or operated with an equal torque and an equal torque gradient
Implementation Method 2
Aging of the first electrical machine and aging of the second electrical machine depend on a thermal load of the first electrical machine and a thermal load of the second electrical machine, respectively
Data Source
AI summary
A vehicle powertrain has a first electrical machine with first power electronics, a second electrical machine with second power electronics, and a transmission connected between the electrical machines and an output. In symmetrical operation, the first and the second electrical machine are operated with an equal torque and torque gradient. When executing a shift non-symmetrical operation, the first and the second electrical machines are operated with different torque and/or torque gradient. During a symmetrical operation if it is detected that a shift with a non-symmetrical operation is to be executed, the symmetrical operation is exited prior to executing the shift to provide a mode in which the electrical machine operated with higher torque and/or torque gradient, is operated with limited torque and/or torque gradient to reduce a temperature of the electrical machine and the associated power electronics operated with a higher torque and/or torque gradient.