Rotor Position Sensor Offset Determination Using q-Current Plausibility
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Solution Overview
Problem
Existing methods for determining the measuring offset of a rotor position sensor in electric machines lack the necessary integrity and accuracy, particularly in automotive applications where torque estimation based on rotor position is critical for safety.
Innovation Solution
The method enhances the integrity and accuracy of measuring offset determination by utilizing q-currents, which are detected with higher integrity levels, and evaluates the plausibility of d-axis candidate values based on q-currents, allowing for the use of less complex and cheaper voltage detection units while maintaining accuracy through a dq-transformation and plausibility criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage detection units with high integrity level are used to determine measuring offset, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent uses q-current as an intermediary parameter to validate the plausibility of d-axis candidate values. Instead of directly relying on high-integrity voltage detection, the system uses the easily measurable q-current (with high integrity level) to indirectly verify the accuracy of the measuring offset determination, thus avoiding the need for complex high-integrity voltage detection units.
Solution Approach 2:
The patent replaces the need for high-integrity voltage detection hardware with a software-based plausibility evaluation method. By using dq-transformation and evaluating the q-current component, the system achieves high-precision measuring offset determination through computational methods rather than hardware upgrades.
2Device complexity
If simple voltage detection units are used, then device complexity is reduced, but measurement precision of measuring offset deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the q-current is used to evaluate the plausibility of determined d-axis candidate values. The system continuously monitors the q-current and uses it to validate whether the measuring offset determination is correct, providing feedback that ensures measurement precision even with simple voltage detection units.
Solution Approach 2:
The patent changes the approach from directly measuring voltages with high integrity to using current measurements (q-current) for validation. By transforming the problem into the dq-coordinate system and using the q-current parameter as a validation criterion, the system achieves high measurement precision without requiring high-integrity voltage detection hardware.
3Reliability
If high integrity level current detection is used for q-current, then reliability of plausibility evaluation is improved, but device complexity increases
Solution Approach 1:
The patent makes the existing current detection unit serve multiple functions: it not only provides current information for motor control but also enables high-reliability plausibility evaluation of the measuring offset. By using the same current detection hardware for dual purposes through dq-transformation, the system achieves high reliability without additional detection devices.
Data Source
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AI summary
Method for determining a measuring offset of a rotor position sensor (5) assigned to a rotor (4) of an electric machine (1), comprising steps of - applying a short circuit to stator windings of the electric machine; - acquiring currents flowing into the stator windings (3) in the short-circuited state; and - determining the measuring offset depending on a q-current determined from the acquired currents.