Rotor Position Sensor Offset Determination Using Phase Line Short-Circuit
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Solution Overview
Problem
Existing methods for determining the measuring offset of a rotor position sensor in electric machines are inefficient and require significant measurement effort, particularly in automotive applications where high automotive safety integrity levels (ASIL) are necessary.
Innovation Solution
A method that computes the measuring offset by short-circuiting the phase lines of an electric machine's stator windings, using both current angle information from the rotor position sensor and impedance information, without requiring voltage measurements, thereby reducing measurement effort and ensuring high ASIL integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electromagnetic-force-based voltage measurement is used to determine measuring offset, then measurement accuracy can be achieved, but measurement effort and complexity increase significantly
Solution Approach 1:
The patent extracts the voltage measurement step from the offset determination process. Instead of measuring voltages induced by electromagnetic forces, the method uses only current measurements combined with impedance information to calculate the offset angle. This removes the complex voltage measurement apparatus and safety measures while maintaining determination accuracy through alternative calculation paths using current angle information and impedance data.
Solution Approach 2:
The patent replaces the electromagnetic-force-based voltage measurement system with an electrical calculation system. Rather than physically measuring electromagnetic-induced voltages requiring specialized sensors and safety infrastructure, the method substitutes this with computational processing of current measurements and impedance parameters to derive the same offset information with reduced hardware complexity.
2Reliability
If voltage measurement with safety measures is performed to achieve ASIL C integrity, then safety integrity level is met, but measurement effort and system complexity increase
Solution Approach 1:
The patent makes the offset determination system self-sufficient by using existing current measurements and impedance information that are already available in the motor control system. The method leverages data that is already being processed for motor control purposes, eliminating the need for separate voltage measurement infrastructure and associated safety measures. The system serves itself by repurposing existing measurement data for offset determination.
Solution Approach 2:
The patent creates a multi-functional approach where the same current measurements and impedance data used for motor control are simultaneously utilized for offset determination. This universal use of existing data streams achieves the required ASIL C integrity without requiring dedicated voltage measurement systems, as the calculation method inherently produces reliable results suitable for automotive safety requirements.
3Measurement precision
If additional voltage measurement apparatus is added to determine offset accurately, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent extracts the offset determination function from the voltage measurement apparatus. By using current measurements and impedance calculations instead of voltage measurements, the method removes the need for additional voltage sensing hardware, signal conditioning circuits, and associated measurement infrastructure while maintaining the capability to accurately determine the offset angle.
Data Source
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AI summary
Method for determining a measuring offset of a rotor position sensor (2) assigned to a rotor (3) of an electric machine (4), wherein stator windings of the electric machine (4) are supplied by phase lines (17) between an inverter (6) and the stator windings, comprising the following steps: - providing a control signal (44) causing the phase lines (17) to be short-circuited when the rotor (3) rotates with a rotation rate; - computing a first current angle information (45) based on a current information, which represents a d-current and a q-current being determined based on a rotor position information (22) provided by the rotor position sensor (2) while the phase lines (17) are short-circuited; and - determining the measuring offset based on the first current angle information (45) and a second current angle information (46) being based on an impedance information (42) concerning the electric machine (4) and on the rotation rate of the rotor (3).