EPS Motor Position Sensor Offset Measurement
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Solution Overview
Problem
Conventional EPS motor systems face challenges in accurately measuring the rotation angle due to mechanical tolerance discrepancies between the motor position sensor and the EPS motor, leading to increased size and cost due to the need for separate EEPROM storage for offset calibration.
Innovation Solution
An apparatus and method that measure the offset between the EPS motor and its position sensor by using a drive motor to generate a back electromotive force signal and a motor position sensor to sense rotation, calculating an offset value to correct the measurement difference, thereby allowing accurate detection of the actual rotation angle without requiring a separate EEPROM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the motor position sensor is mounted inside the EPS motor, then the measurement precision of rotation angle is improved, but the device complexity and size increase due to requiring separate EEPROM storage
Solution Approach 1:
The patent merges the offset calibration functionality into the ECU by utilizing its existing EEPROM memory, eliminating the need for a separate EEPROM in the motor assembly. The offset value is stored in the ECU's memory space, integrating the calibration data storage function into the existing control unit and reducing overall device complexity.
Solution Approach 2:
The ECU's EEPROM is used for multiple purposes: storing both the offset calibration values and the normal operational control data. This multi-functional use of the existing memory resource eliminates the need for dedicated separate storage, reducing device complexity while maintaining measurement precision.
2Measurement precision
If the motor position sensor is mounted inside the EPS motor, then the measurement precision of rotation angle is improved, but the volume of the EPS motor increases
Solution Approach 1:
The patent combines the offset storage function with the ECU's existing memory resources, eliminating the need for a separate EEPROM component in the motor assembly. This integration removes the additional volume that would be required for separate storage hardware while maintaining the ability to store calibration data.
3Reliability
If a separate EEPROM is provided for storing offset value, then the reliability of offset calibration is improved, but the device complexity and cost increase
Solution Approach 1:
The ECU's EEPROM is utilized for dual purposes: storing offset calibration values and storing operational control data. This multi-functional approach maintains the reliability of offset calibration by providing dedicated storage space within the existing memory architecture, while avoiding the added complexity of separate dedicated storage hardware.
Solution Approach 2:
The patent merges the offset calibration storage function into the ECU's existing memory system, combining multiple storage functions into a single integrated solution. This eliminates the need for separate EEPROM hardware while maintaining data integrity and calibration reliability through the ECU's established memory management protocols.
4Volume of moving object
If the motor position sensor is mounted outside the EPS motor, then the volume of EPS motor is reduced, but the measurement precision of rotation angle deteriorates due to mechanical tolerance
Solution Approach 1:
The patent introduces an offset parameter that compensates for the mechanical tolerance between the externally mounted sensor and the motor center. By calculating and applying this offset value, the system corrects the measurement error caused by the external mounting position, thereby restoring measurement precision while maintaining the volume reduction benefit of external sensor placement.
Solution Approach 2:
The offset value acts as an intermediary correction factor between the externally mounted sensor and the actual motor rotation angle. This intermediary parameter compensates for the positional discrepancy, allowing accurate angle measurement despite the sensor being mounted outside the motor where mechanical tolerance would otherwise cause errors.
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 solution reduces the size of the EPS motor by mounting the position sensor externally, eliminates the need for a separate EEPROM, and ensures accurate rotation angle detection by compensating for measurement discrepancies, enhancing the reliability of the motor position sensor's measurements.
Implementation Method 1
a back electromotive force measurement unit that measures a back electromotive force generated by the EPS motor so as to generate a back electromotive force signal
Implementation Method 2
a motor position sensor that is installed outside the EPS motor and senses the rotation of the EPS motor so as to generate a position signal
Data Source
AI summary
The present invention relates to an apparatus for measuring an offset of an EPS motor position sensor and a method therefor, the apparatus comprising: a drive motor that drives an EPS motor at a predetermined constant speed; a back electromotive force measurement unit that measures a back electromotive force generated by the EPS motor so as to generate a back electromotive force signal; a motor position sensor that senses the rotation of the EPS motor so as to generate a position signal; and an offset calculation unit that calculates an offset value by using a difference between the back electromotive force signal measured in the back electromotive measurement unit and the position signal generated by the motor position sensor.