Rotor Bearing Angle Sensing for Precise EV Drivetrain Torque
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Solution Overview
Problem
Existing methods for determining torque in electrically operated motor vehicles are inaccurate, particularly in applications where separate electric motors drive vehicle wheels, leading to unwanted torque differences that affect vehicle tracking.
Innovation Solution
A device using two rolling bearings with angular position sensors to measure the angular position of a rotor, transmitting signals to a vehicle controller to determine torque differences and improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If indirect torque determination from process data is used, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent replaces indirect estimation methods with direct mechanical measurement using angular position sensors on rolling bearings. The torsion angle is mechanically captured through the relative angular positions of the rotor at different axial locations, providing direct torque measurement instead of indirect calculation from electrical parameters.
Solution Approach 2:
The patent introduces angular position sensors on rolling bearings as intermediary measurement elements. These sensors measure the angular position of the rotor at different axial locations, and the difference in angular positions serves as an intermediary parameter that directly reflects the torsion angle and torque, bridging the gap between mechanical rotation and torque measurement.
2Measurement precision
If two rolling bearings with angular position sensors are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The rolling bearings serve multiple functions: they support the rotor mechanically and simultaneously host angular position sensors for torque measurement. This multi-functionality reduces the need for separate measurement components, thereby limiting the increase in device complexity while achieving precise torque determination.
Solution Approach 2:
The patent merges the torque measurement function with the existing rolling bearing structure. By integrating angular position sensors into the rolling bearings that already support the rotor, the system combines structural support and measurement functions into a single integrated component, reducing overall system complexity.
3Measurement precision
If rolling bearings are spaced at greatest possible axial distance, then measurement precision is improved, but length of rotor increases
Solution Approach 1:
The patent employs dynamic adjustment of the axial spacing between rolling bearings based on specific application requirements. The spacing can be optimized for different operating conditions, allowing the system to adapt between maximizing measurement precision (larger spacing) and minimizing rotor length (smaller spacing) depending on the operational context.
Data Source
AI summary
A device for determining a torque in a drivetrain of an at least partially electrically operated motor vehicle is provided, having a first electric motor with a first rotor rotatably mounted in at least two rolling bearings spaced in the axial direction. The first rotor is operatively connected to at least a first vehicle wheel to be driven by the first electric motor. The first rolling bearing has a first angular position sensor and the second rolling bearing has a second angular position sensor, the sensors each generating a signal that represents the angular position of the first rotor at the particular bearing point. The signals are transmitted to a vehicle controller, in which the torque of the first electric motor applied to the first rotor is determined from the difference between the angular positions and is provided to control the motor vehicle.